1B- Atom Structure, Bonding

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Topic 2 Microscopic World I

Part A Unit-based exercise

Unit 5 Atomic structure

Fill in the blanks

1 All elements are made of atoms .

2 Elements exist in different states at room

conditions. Silver and sulphur are solids ;

bromine and mercury are liquids ; chlorine

and oxygen are gases .

3 Elements can be classified into three main

groups: metals , metalloids and

non-metals .

4 The melting and boiling points of non-metals are

usually low .

5 Metals are usually good conductors of

heat and electricity.

6 Boron , silicon and germanium

are metalloids.

7 Atoms consist of a nucleus in the centre

and a cloud of electrons that move in

circular orbits called shells .

8 The nucleus of an atom contains two types of

particles : protons and neutrons .

9 The number of protons in an atom of an

element equals the atomic number of the

element.

10 The sum of the numbers of protons and neutrons

in an atom equals the mass number of

the atom.

11 Different atoms of an element with the same

number of protons but different number of

neutrons are isotopes .

12 The weighted average relative isotopic mass

of all the naturally occurring isotopes of an

element on the 12C = 12.00 scale is the relative

atomic mass of that element.

13 The way in which electrons are arranged in an

atom is its electronic arrangement .

14 The electronic arrangement of an atom can be

represented by an electron diagram.

15 In a hydrogen atom, the region in which there is

95% chance of finding the electron is called an

orbital .

True or false

Decide whether each of the following statements is true or false.

16 At room temperature and pressure, all F

metals are solids.

17 Solid non-metals are usually dull in T appearance.

18 Silicon is a metalloid. T

19 Molten sulphur is a good conductor F of electricity.

20 The symbol of magnesium is Ma. F

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21 The atomic number of an element T

equals the number of electrons in an atom of that element.

22 An atom of an element must F

contain equal number of protons and neutrons.

23 All atoms contain neutrons. F

24 A sodium atom (123

1Na) contains 11 F

neutrons.

25 A fluorine atom contains 9 electrons. T

26 Isotopes of an element have the same T

number of protons.

27 Isotopes of an element have the same F

mass.

28 The atomic number of oxygen is 8. T

29 In an atom, the second electron shell F

can hold a maximum of 10 electrons.

30 A calcium atom contains 3 occupied F

electron shells.

Multiple choice questions

31 Which of the following combinations is correct?

Element Symbol

A Calcium CB Chlorine ChC Iron IrD Potassium K D

32 Which of the following elements is a gas at room temperature and pressure?

A CarbonB IronC OxygenD Silicon C

33 Which of the following elements is a solid at room temperature and pressure?

A ClB NC NeD S D

34 Which of the fol lowing conbinations is INCORRECT?

Element State at room temperature and pressure

A Argon gasB Beryllium liquidC Calcium solidD Phosphorus solid B

35 Consider the information below:

Element Melting point (°C) Boiling point (°C)

W –200 –45

X 1 245 1 869

Y –58 37

Z 52 114

Which of the following elements is a gas at 25 °C?

A WB XC YD Z A

36 The table shows the melting points and boiling points of four substances at 1 atm pressure.

Substance Melting point (°C) Boiling point (°C)

W –189 –186

X –110 –40

Y –7 60

Z –90 10

Which of the following substances exists as a liquid at –100 °C and 1 atm pressure?

A WB XC YD Z B

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37 Consider the following information:


W –50 5

X 4 81

Y 68 104

Z –95 69

Which of the following substances is / are in liquid state at room temperature and pressure?

A W onlyB X onlyC X and Z onlyD Y and Z only C

38 Which of the following elements is a metal?

A AluminiumB CarbonC GermaniumD Neon A

39 Which of the fol lowing elements is a metalloid?

A BoronB CopperC HeliumD Phosphorus A

40 Which of the following elements is a non-metal?

A BaB BeC CsD Kr D


SolidMelting

pointElectrical

conductivitySolubility in

water

W low non-conducting soluble

X high non-conducting soluble

Y high good insoluble

Z very high non-conducting insoluble

Which of the following solids is likely to be a metal?

A WB XC YD Z C

42 Which of the following statements concerning silicon is INCORRECT?

A Properties of silicon are in between metals and non-metals.

B Silicon is brittle.C S i l icon can be used to make semi-

conductors.D Silicon is soluble in water. D

43 Which of the following statements concerning the basic structure of an atom is correct?

A An atom must have equal numbers of protons and neutrons.

B The mass of one proton is approximately equal to that of an electron.

C A neutron carries a small negative electrical charge.

D A proton carries a small positive electrical charge.

D

44 The atomic number of an element X is 10. An atom of X has a mass number 22. Which of the following combinations concerning the atom of X is correct?

Number of Number of Number of protons neutrons electrons

A 10 12 10B 10 12 12C 12 10 10D 12 10 12 A

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45 An atom has 28 electrons and 30 neutrons. Which of the following combinations concerning the atom is correct?

Atomic number Mass number

A 28 30B 28 58C 30 28D 58 28 B

46 Which of the following combinations concerning the atomic structure of the atom 2

513X is correct?


A 51 23 51B 28 51 23C 23 28 23D 23 23 28 C

47 Which of the following particles contains the same number of neutrons as 1

326S?

A 1231Na

B 1242Mg

C 1284Si

D 1315P D

48 Which of the following combinations concerning isotopes of an element is correct?

Number of Number of Number of neutrons protons electrons

A different same differentB same different sameC different same sameD same same same

C

49 Consider the following information of four atoms:

AtomAtomicnumber

Massnumber

Number ofneutrons

I 37 20

II 19 39

III 20 20

IV 41 22

Which of the following atoms are isotopes?

A I and IIIB II and IIIC I and IVD II and IV D

50 The following table shows the relative abundance of isotopes of lithium:

Isotope Relative abundance (%)

6Li 7.4

7Li 92.6

The relative atomic mass of lithium is

A 6.07.B 6.93.C 6.07 g.D 6.93 g. B

51 Element X has two isotopes, 85X and 87X. The table below lists the relative abundance of each isotope.


85X 72.1

87X 27.9

What is the relative atomic mass of X?

A 85.2B 85.6C 86.2D 86.6 B

52 Metal X has three isotopes, 189X, 190X and 192X. The graph below shows the relative abundance of the isotopes.

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What is the relative atomic mass of X?

A 189.7B 190.3C 190.7D 191.3 C

53 Element X occurs in nature as two isotopes, 79X and 81X. If the relative atomic mass of X is 79.9, what is the relative abundance of the 81X isotope?

A 30.0%B 35.0%C 40.0%D 45.0% D

54 The relative atomic mass of potassium is 39.1. It is NOT a whole number because

A the mass of electrons has been taken into account.

B fractional protons exist.C fractional neutrons exist.D isotopes of potassium exist. D

55 The atomic mass of element X is 69.7. X has two isotopes, 69X and aX, and the relative abundance of 69X is 65.0%. What is the value of a?

A 70B 71C 72D 73 B

56 The atomic number of an element X is 15. The electronic arrangement of an atom of X is

A 2,13.B 2,8,5.C 2,10,3.D 2,4,8,1. B

57 Which of the following represents the electronic arrangement of an atom of a metalloid?

A 2,1B 2,2C 2,3D 2,4 C

58 The electron diagram of an atom of element X is shown below:

(Only electrons in the outermost shell are shown.)

X could be

A Cl.B P.C S.D Si. C

59 Which of the following descriptions of metals is / are correct?

(1) They are all solids at room conditions.(2) They are good conductors of electricity.(3) They are all stored in paraffin oil.

A (1) onlyB (2) onlyC (1) and (3) onlyD (2) and (3) only B

60 Which of the following descriptions concerning non-metals are correct?

(1) Their melting points are often low.(2) They are brittle if they are solids.(3) They are poor conductors of heat.

A (1) and (2) onlyB (1) and (3) onlyC (2) and (3) onlyD (1), (2) and (3) D

61 Which of the following statements concerning metalloids is / are correct?

(1) All metalloids are solids.(2) Gallium is a metalloid.(3) Metalloids cannot conduct electricity at

room temperature.

A (1) onlyB (2) onlyC (1) and (3) onlyD (2) and (3) only A

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62 Which of the following statements concerning isotopes of an element is / are correct?

(1) They have different number of neutrons.(2) They have different atomic numbers.(3) They have the same mass.


63 Consider the following information concerning atoms P and Q:

AtomNumber of

protonsNumber ofneutrons

Number ofelectrons

P 15 16 15

Q 16 16 16

Which of the following statements concerning P and Q is / are correct?

(1) P is an atom of a non-metal.(2) Q is an atom of a metal.(3) P and Q are isotopes of the same

element.



Particle

X Y Z

Number of protons 8 8 10

Number of electrons 8 8 10

Number of neutrons 10 8 10

Which of the following statements concerning the particles is / are correct?

(1) X and Z have the same mass.(2) X and Y are isotopes.(3) Y and Z have the same electronic

arrangement.


65 The atomic number of element X is 15. It has only one isotope with a mass number 31.

Which of the following statements concerning X is / are correct?

(1) X is a gas at room temperature and pressure.

(2) There are 5 electrons in the outermost shell of an atom of X.

(3) There are 15 neutrons in the nucleus of an atom of X.


66 An atom of element X has an electronic arrangement 2,8,1. Which of the following statements concerning X are correct?

(1) It is a metal.(2) Its atom has 11 protons.(3) Its symbol is K.

A (1) and (2) onlyB (1) and (3) onlyC (2) and (3) onlyD (1), (2) and (3) A

67 The isotope cobalt-60 (260

7Co) is used to destroy cancer cells in the human body. Which of the following statements concerning a 2

607Co atom

are correct?

(1) It contains 33 neutrons.(2) It contains 27 protons.(3) The number of electrons it has is different

from another isotope of cobalt.


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Directions : Each question (Questions 68 – 75) consists of two separate statements. Decide whether each of the two statements is true or false; if both are true, then decide whether or not the second statement is a correct explanation of the first statement. Then select one option from A to D according to the following table :

A Both statements are true and the 2nd statement is a correct explanation of the 1st statement. B Both statements are true but the 2nd statement is NOT a correct explanation of the 1st statement. C The 1st statement is false but the 2nd statement is true. D Both statements are false.

1st statement 2nd statement

68 Carbon is a solid at room temperature and Carbon is a non-metal. B

pressure.

69 Atoms are electrically neutral. Atoms have the same number of protons A

and electrons.

70 The number of neutrons and that of protons An atom is electrically neutral. C

in an atom should be the same.

71 The atomic number of sulphur (132

6S) is 16. A 1326S atom contains 16 neutrons. B

72 2544X and 2

546Y are isotopes. 2

544X and 2

546Y have the same mass number C

but different atomic numbers.

73 Isotopes of a given element have different Isotopes of a given element have different A relative isotopic masses. numbers of neutrons.

74 The relative atomic mass of magnesium is not a Magnesium has isotopes. A

whole number.

75 Isotopes of an element have the same mass. All atoms of an element contain the same C

number of electrons.

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Unit 6 The periodic table

Fill in the blanks

1 In the periodic table, the elements are arranged

in order of increasing atomic number .

2 The vertical columns in the periodic table

are groups . The horizontal rows

are periods .

3 The number of outermost shell electrons in an

atom of an element equals the group number

of the element.

4 The number of occupied electron shells in an atom

of an element equals the period number

of the element.

5 Across a period of the periodic table, the

e lements change from metals through

metalloids to non-metals .

6 Group I elements are called alkali metals.

7 Group I elements are stored in paraffin oil in

the laboratory.

8 T h e re a c t i v i t y o f G ro u p I e l e m e n t s

increases as we move down the group.

9 Sodium reacts with water to give hydrogen

gas and sodium hydroxide .

10 Group II elements are called alkaline earth

metals.

11 Group VII elements are called halogens .

12 There is a gradual change in the intensity of

the colour of Group VII elements. Chlorine

is greenish yellow in colour, bromine

is reddish brown in colour while iodine

is black in colour.

13 The react i v i t y o f Group V I I e lements

decreases as we move down the Group.

14 Group 0 elements are called noble gases .

15 The octet rule states that atoms become

stable by having eight electrons in their outermost

shells.

16 Argon is used to fill electric light bulbs.

17 When an atom of an element loses one or more

electrons, it forms a positive ion.

18 When an atom of an element gains one or more

electrons, it forms a negative ion.

19 A magnesium atom tends to lose 2 electrons

to form an ion. A magnesium ion has

12 protons and 10 electrons.

20 A nitrogen atom tends to gain 3 electrons

to form an ion. A nitride ion has 7 protons

and 10 electrons.

True or false


21 In the periodic table, the elements are F

arranged in order of increasing atomic mass.

22 Group number of an element equals the T

number of outermost shell electrons in an atom of the element.

23 Elements in the second period of the T

periodic table show a gradual changefrom having metallic property to having non-metallic property.

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24 Across the third period of the periodic F

table, the elements show a gradual increase in the number of occupied electron shells in their atoms.

25 Sulphur belongs to Period 2 of the F

periodic table.

26 Aluminium is a Group III element. T

27 Sodium is an alkali metal. T

28 Argon is a halogen. F

29 Magnesium is an alkaline earth metal. T

30 Neon belongs to Group 0 of the periodic T table.

31 Potassium is stored in paraffin oil in the T

laboratory.

32 The melting point of sodium is higher F

than that of lithium.

33 Beryllium and calcium have the same F

chemical properties.

34 Bromine is a volatile liquid. T

35 Iodine vapour is brown in colour. F

36 The boiling point of halogens increases T

as we move down the group.

37 35Cl and 37Cl have different chemical F properties.

38 A helium atom has an octet structure F in its outermost shell.

39 All Group 0 elements are colourless T gases at room temperature and pressure.

40 An oxygen atom gains 2 electrons to T form a stable oxide ion.


41 Which of the following statements concerning the periodic table is correct?

A Elements are arranged in order of increasing mass number.

B The vertical columns are called periods.C The horizontal rows are called groups.D Non-metals are found on the right. D

42 Which of the following statements concerning elements in the same group is correct?

A Their atoms have the same number of occupied electron shells.

B They have the same atomic number.C Their atoms have the same number of

outermost shell electrons.D Their chemical properties are the same.

C

43 Which of the following statements concerning elements in Period 2 of the periodic table is correct?

A They have similar chemical properties.B The atom of each element has 2 outermost

shell electrons.C The atom of each element has two occupied

electron shells.D Across the period, the elements change from

metalloids to metals. C

44 To which group does carbon belong?

A Group IIB Group IVC Group VID Group 0 B

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45 The electron diagram of an atom of element X is shown below:

X belongs to

A Group II.B Group IV.C Group VI.D Group 0. C

46 An atom of element X has 2 completely filled shells only. X is in

A Group 0.B Group II.C Group IV.D Group VI. A

47 To which group does the element 1315X belong?

A Group IB Group IIIC Group VD Group VII C

48 Which of the following combinations is correct?

Element Group number

A Boron IIB Bromine VIIC Chlorine VD Silicon III B

49 Which of the following pairs of elements belongs to the same group?

A Argon and neonB Carbon and chlorineC Calcium and potassiumD Magnesium and sodium A

50 Lithium and sodium show similar chemical properties because they

A are both metals.B have the same atomic number.C have the same electronic arrangement in their

atoms.D have the same number of outermost shell

electrons in their atoms. D

51 Which of the following pairs of atomic numbers corresponds to elements with similar chemical properties?

A 7 and 13B 9 and 17C 11 and 18D 14 and 20 B

52 Element X and aluminium belong to the same group. The atomic number of X could be

A 6.B 23.C 26.D 31. D

53 To which period does sulphur belong?

A Period 2B Period 3C Period 4D Period 5 B

54 Which of the following pairs of elements belong to the same period?

A Argon and aluminiumB Beryllium and siliconC Chlorine and nitrogenD Phosphorus and oxygen A

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55 Elements X and Y are in the same period of the periodic table. Which of the following statements concerning X and Y is correct?

A They have the same relative atomic mass.B Their atoms have the same number of occupied

electron shells.C Their atoms have the same number of

outermost shell electrons.D They have similar chemical properties.

B

56 The atomic number of an element X is 9. Which of the following statements concerning X is INCORRECT?

A X is a non-metal.B X belongs to Period 2 of the periodic table.C X is a gas at room temperature and

pressure.D X belongs to Group II of the periodic table.

D

57 Which of the following statements concerning sodium is correct?

A It is more reactive than potassium.B It gives a lilac flame in flame test.C It floats on water.D It reacts with water to form oxygen gas.

C

58 Which of the following graphs can represent the variation of the melting point of the Group I elements, Na, K, Rb and Cs, with increasing atomic number?

A B

DC

A

59 Which of the following statement concerning chlorine is correct?

A It is a reddish brown gas.B Its atom has 7 outermost shell electrons.C It is used to manufacture sodium chloride.D It is more reactive than fluorine. B

60 Consider the following elements:

Element Atomic number

W 4

X 11

Y 12

Z 19

Which of the following elements is the most reactive metal?

A WB XC YD Z D

61 A solid element X has a melting point of 650 °C. X conducts electricity and reacts readily with dilute hydrochloric acid to give hydrogen. X is probably a

A Group II element.B Group IV element.C Group VI element.D Group 0 element. A

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62 Which of the following statements concerning calcium is correct?

A It is in Period 4 of the periodic table.B It is an alkali metal.C It reacts with metals to form salts.D It catches fire when reacting with cold

water. A

63 Which of the following graphs shows the trend in the boiling points of the halogens?

A B

C D

C

64 Which of the following statements concerning chlorine, bromine and iodine is INCORRECT?

A They are all coloured substances.B They are all poisonous.C Their reactivity increases with relative atomic

mass.D They all react with sodium sulphite solution.

C

65 Argon is used to fill electric light bulbs because it

A is cheap.B is unreactive.C glows when hot.D is colourless. B

66 Which of the following statements concerning noble gases is INCORRECT?

A They are all colourless gases.B All of them have little reactivity.C All of their atoms have 8 outermost shell

electrons.D Their boiling points increase from helium to

argon. C

67 A and B are two noble gases. If the atomic number of A is x, then the atomic number of B could be

A x – 8.B x – 2.C x + 10.D x + 16. A

Directions: Questions 68 – 69 refer to the portion of the periodic table shown below.

68 Which is the most reactive metal?

A aB bC gD h C

69 Which is a liquid at room temperature and pressure?

A cB dC eD j D

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ElementMelting

point (°C)Density(g cm–3)

Electricalconductivity

W 98 0.97 good

X 113 2.07 non-conducting

Y 838 1.74 good

Z 1 744 11.3 good

Which of the following is likely to be a Group I element?

A WB XC YD Z A

71 Rubidium and potassium belong to the same group of the periodic table. The relative atomic mass of rubidium is larger than that of potassium. Which of the following statements concerning rubidium is probably correct?

A It has a very high melting point.B Its atom has 2 outermost shell electrons.C It is very hard.D It is more reactive than potassium. D

72 Strontium and calcium belong to the same group of the periodic table. Which of the following statements concerning strontium is correct?

A It can be extracted from its ore by physical methods.

B Its atom has one outermost shell electron.C It tarnishes when exposed to the air.D It floats on water. C

73 Krypton belongs to the same group as neon in the periodic table. Which of the following statements concerning krypton is INCORRECT?

A An atom of krypton has an octet structure in its outermost shell.

B Krypton belongs to Period 3 of the periodic table.

C Krypton is a colourless gas at room temperature and pressure.

D A balloon full of krypton falls in the air. B

74 Which of the following descriptions for the formation of a stable ion from a magnesium atom is correct?

A The magnesium atom gains two neutrons.B The magnesium atom loses two electrons.C The mass number of the magnesium atom

decreases by 2.D The atomic number of the magnesium atom

decreases by 2. B

75 Which of the following pairs of species has the same number of electrons?

A Li+ and HB O2– and Cl–

C Na+ and S2–

D Ne and F– D

76 An iron atom 2566Fe forms a Fe3+ ion. Which of

the following combinations concerning the Fe3+ ion is correct?


A 29 30 23B 29 27 26C 26 30 23D 26 27 26 C

77 X is an element and the X2+ ion has an electronic arrangement 2,8,8. Which of the following statement concerning X is correct?

A X is a halogen.B X is an alkali metal.C X is a transition metal.D X is a Period 4 element. D

78 An anion carries 1 negative charge. It has 36 electrons. How many protons does the anion have?

A 34B 35C 36D 37 B

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79 M is an element. The M2+ ion has 34 neutrons and 28 electrons. What is M?

A GeB NiC SeD Zn D

80 Consider the following information of particles X and Y :

ParticlesNumber of

protonsNumber ofelectrons

Number ofneutrons

X 8 10 8

Y 8 8 10

Which of the following statements is correct?

A X and Y are isotopes.B X and Y are atoms of different elements.C X is an anion.D Y is a cation. C

81 In moving from Group I to Group VII across the second period of the periodic table, which of the following statements is / are correct?

(1) The elements show a gradual increase in atomic size.

(2) The elements change from metallic to non-metallic across the period.

(3) The elements show a gradual decrease in melting point.


82 Which of the following descriptions is / are true when going down Group IV of the periodic table?

(1) The elements show a gradual increase in relative atomic mass.

(2) The elements show a gradual increase in atomic size.

(3) The elements show a gradual increase in the number of outermost shell electrons in their atoms.

A (1) and (2) onlyB (1) and (3) only C (2) and (3) onlyD (1), (2) and (3) A

83 Element X has an isotope 40 18X. Which of the

following statements is / are correct?

(1) X is in Period 3 of the periodic table.(2) X is in Group VI of the periodic table.(3) 40

18X has 18 neutrons.


84 There is a gradual change in the properties of alkali metals from lithium to potassium. Which of the following properties are in the orderlithium < sodium < potassium?

(1) Atomic size(2) Chemical reactivity(3) Melting point


85 Which of the following statements concerning Group II elements is / are correct?

(1) Their atoms have 2 outermost shell electrons.

(2) They are less dense than water.(3) They are stored in water in the

laboratory.


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86 Which of the following statements concerning halogens is / are correct?

(1) Their reactivity increases with relative atomic mass.

(2) Bromine is a volatile liquid.(3) Iodine vapour is purple in colour.

A (1) onlyB (2) onlyC (1) and (3) onlyD (2) and (3) only D

87 Consider the following information about three elements, X, Y and Z.


X 11

Y 16

Z 17

Which of the following statements concerning X, Y and Z are correct?

(1) X, Y and Z belong to the same period of the periodic table.

(2) X is an alkaline earth metal.(3) Y and Z are non-metals.

A (1) and (2) onlyB (1) and (3) onlyC (2) and (3) onlyD (1), (2) and (3) B

88 Helium is used to fill airships because

(1) its density is very low.(2) it does not burn.(3) the air contains a high percentage by

volume of it.


89 Which of the following statements concerning noble gases are correct?

(1) All noble gases have 8 outermost shell electrons in their atoms.

(2) Their relative atomic masses increase down the group.

(3) They are all colourless gases at room temperature and pressure.

A (1) and (2) onlyB (1) and (3) onlyC (2) and (3) onlyD (1), (2) and (3) C

90 The atomic number of element X is 12. Which of the following statements concerning X are correct?

(1) X tarnishes when exposed to the air.(2) X sinks in water.(3) X is extracted by electrolyzing its molten

ore.


91 Caesium (Cs) is a Group I element. Which of the following statements concerning caesium are correct?

(1) It reacts with water to give an alkaline solution.

(2) It gives a characteristic flame colour in flame test.

(3) Its melting point is less than 100 °C.


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92 Strontium is a Group II element below calcium in the periodic table. Which of the following statements concerning strontium are correct?

(1) It forms an ion carrying two negative charges.

(2) It is more reactive than calcium.(3) It reacts with non-metals to form salts.


93 There is a gradual change in the properties of halogens from chlorine to iodine. Which of the following properties are in the orderchlorine < bromine < iodine?

(1) Reactivity(2) Density(3) Atomic size


94 Astatine is a Group VII element below iodine in the periodic table. Which of the following statements concerning astatine is / are probably correct?

(1) It is colourless.(2) Its atom has 7 outermost shell electrons.(3) It is a solid at room temperature and

pressure.


95 The electronic arrangement of an atom of element X is 2,8,18,18,8,2. Which of the following statements concerning X are correct?

(1) It is denser than water.(2) It gives a characteristic flame colour in

flame test. (3) It reacts with dilute hydrochloric acid to

give hydrogen.


96 Which of the following particles is / are present in a H+ ion?

(1) Proton(2) Neutron(3) Electron


97 Which of the following statements concerning the formation of an oxide ion from an oxygen atom is / are correct?

(1) An oxygen atom and an oxide ion have the same number of occupied electron shells.

(2) The atomic number of the oxygen atom increases by 2.

(3) The mass number of the oxygen atom increases by 2.


98 Which of the following species has / have the same electronic arrangement as a neon atom?

(1) O2–

(2) Li+

(3) K+


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99 Atom X can form a stable ion X–. Which of the following statements is / are correct?

(1) Ion X– has one more neutron than atom X.

(2) Both atom X and ion X– have the same nuclear charge.

(3) Ion X– has one more occupied electron shell than atom X.


100 X, Y and Z are three consecutive elements in the periodic table. X forms a stable anion X–, while Z forms a stable cation Z+. Which of the following statements about X, Y and Z is / are correct?

(1) X– and Z+ have the same electronic arrangement.

(2) X– and Z+ have the same number of protons.

(3) X, Y and Z belong to the same period.





101 Elements are arranged in order of their atomic Atomic numbers are always whole numbers B

numbers, rather than relative atomic masses, while there are fractional relative atomic in the periodic table. masses.

102 Lithium and neon belong to the same period Atoms of lithium and neon have the same A

of the periodic table. number of occupied electron shells.

103 Nitrogen and oxygen belong to the same period Nitrogen and oxygen are colourless gases. B

of the periodic table.

104 Across the second period of the periodic table, Across the second period of the periodic D

the elements show a gradual increase in table, the elements show a gradual melting point. increase in the number of occupied electron shells in their atoms.

105 Across the third period of the periodic table, Across the third period of the periodic table, B

the atomic size of the elements. the metallic character of the elements decreases.

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106 Sodium and potassium show similar chemical Atoms of sodium and potassium have the A properties. same number of outermost shell electrons.

107 The density of Group II elements decreases The reactivity of Group II elements decreases D

down the group. down the group.

108 The reactivity of halogens increases down the The atomic size of halogens increases down C

group. the group.

109 The elements in Group 0 of the periodic table The outermost shell of an atom of a A are very unreactive. Group 0 element is completely filled.

110 A chloride ion and an argon atom show similar A chloride ion and an argon atom have the C

chemical properties. same electronic arrangement.

Unit 7 Ionic and metallic bonds

Fill in the blanks

1 Substances can be classified into groups according

to how they conduct electricity.

a) Substances which conduct electricity but are

not chemically changed during conduction are

conductors .

b) Compounds which conduct electricity in molten

state or aqueous solution and are

decomposed by electricity during conduction

are electrolytes .

c) Substances which do not conduct electricity

are non-conductors .

2 When metal atoms combine with non-metal

atoms, ionic bonds result.

3 When electricity is passed through molten

lead(II) bromide, lead(II) ions move towards the

negative electrode while bromide ions move

towards the positive electrode.

4 An ion that forms from a group of atoms is called

a polyatomic ion.

5 A sulphate ion is formed from one sulphur atom

and four oxygen atoms. The whole group

of atoms carries two negative charges.

6 A sulphite ion is formed from one sulphur atom

and three oxygen atoms. The whole group

of atoms carries two negative charges.

7 An aqueous solution of potassium permanganate

is purple in colour. This colour comes from

the permanganate ions.

8 The green colour of jade is due to the presence

of chromium(III) ions.

9 A chemical formula is a way of representing a

chemical substance using symbols and figures.

10 A metallic bond is a type of bond in which

positive metal ions are held together by a ‘sea’

of mobile electrons.

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True or false


11 An ionic bond is the strong forces of F

attraction between ions of the same charge.

12 Ionic bond usually occurs when metals F

combine.

13 When calcium combines with fluorine, T

each calcium atom loses two electrons and each fluorine atom gains one electron.

14 Element X (atomic number 11) combines F

with element Y (atomic number 16) to form a compound with the chemical formula XY2.

15 Magnesium combines with oxygen to T

form a compound with the chemical formula MgO.

16 Element X (atomic number 20) reacts T

with element Y (atomic number 7) to form a compound with the chemical forumla X3Y 2.

17 The chemical formula of the compound F

formed between astatine (At) and potassium is KAt2.

18 An aqueous solution of iron(II) sulphate is F

yellow-brown in colour.

19 An aqueous solution of potassium T

dichromate is orange in colour.

20 Metallic bond is a type of bond in which F

positive metal ions are held together by a ‘sea’ of negative ions.


21 Which of the following substances is a non-conductor of electricity?

A AlcoholB CopperC GraphiteD Molten potassium chloride A

Directions: Questions 22 and 23 refer to the following experiment.

The circuit shown below is set up and the solid lead(II) bromide is heated until it becomes molten.

22 Which of the following statements concerning the experiment is INCORRECT?

A The bulb lights up.B Nichrome wires can be used as electrodes.C A reddish brown gas is evolved at electrode

Y.D The experiment should be carried out in a

fume cupboard. C

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23 Which of the following can be deduced from the experimental results?

A Molten lead(II) bromide can be decomposed by electricity.

B Solid lead(II) bromide is a non-electrolyte.C Metallic bonds exist in molten lead(II)

bromide.D Solid lead(II) bromide is a covalent compound

but molten lead(II) bromide is an ionic compound.

A

24 Which of the following pairs of elements will

combine to form an ionic compound?

A Copper and magnesiumB Lithium and sodiumC Potassium and oxygenD Silicon and hydrogen C

25 Consider the atomic numbers of four elements.

Element a b c d

Atomic number 6 9 10 11

Which of the following pairs of elements will combine to form an ionic compound?

A a and bB a and cC b and dD c and d C

26 A part of the periodic table is shown below.

Which of the following elements will combine with element d to form an ionic compound?

A aB bC cD e B

27 In which of the following substances do metallic

bonds exist?

A CopperB Copper(II) sulphateC Sodium chlorideD Silicon A

28 Which of the following is an electron diagram of potassium oxide?

A

B

C

D

C

29 Elements X and Y form a compound with the following electron diagram:

(Only electrons in the outermost shells are shown.)

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Which of the following combinations is correct?

X Y

A Al ClB Ca SC Li OD Mg Br B

30 The atomic number of element X is 12. X reacts with element Y to form an ionic compound with the chemical formula XY2. To which group of the periodic table does Y belong?

A Group IIB Group VC Group VID Group VII D

31 The atomic number of element X is 11. X reacts with element Y to form an ionic compound with the chemical formula X2Y. To which group of the periodic table does Y belong?

A Group IB Group IVC Group VID Group VII C

32 Elements X and Y belong to the first three periods of the periodic table. The compound formed between these two elements has the following electronic structure:


How many electrons are there in the outermost shell of an atom of X and that of Y?

X Y

A 1 2B 1 5C 2 5D 2 8 C

33 An ionic compound has the chemical formula XY where X and Y represent the cation and anion respectively. If both X and Y have the same electronic arrangement, the compound may be

A aluminium oxide.B magnesium oxide.C lithium fluoride.D sodium chloride. B

34 The atomic number of an element X is 7. What is the chemical formula of the compound formed between magnesium and X?

A MgXB MgX2

C Mg2X3

D Mg3X2 D

35 An atom of element X has 13 protons while an atom of element Y has 8 electrons. What is the chemical formula of the compound formed between X and Y?

A XYB XY3

C X2Y3

D X3Y2 C

36 Elements X and Y form a compound with the following electronic structure:


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Which of the following combinations is correct?

X Y

A B HB Li NC Mg ClD Na O B

37 Which of the following pairs of elements would react with each other most vigorously?

A Chlorine and lithiumB Chlorine and potassiumC Fluorine and lithiumD Fluorine and potassium D

38 Consider the information given in the table below:


w 9

x 14

y 18

z 20

Which of the following pairs of elements would react with each other most readily?

A w and yB w and zC x and yD x and z B

39 Which of the following ions is a polyatomic ion?

A Ammonium ionB Chloride ionC Magnesium ionD Sulphide ion A

40 Which of the following compounds, when dissolved in water, gives a green solution?

A Cobalt(II) chlorideB Magnesium chlorideC Nickel(II) sulphateD Potassium permanganate C

41 Which of the following ions is responsible for the greenish blue colour of turquoise?

A Copper(II) ionB Dichromate ionC Iron(III) ionD Manganese(III) ion A

42 Which of the following ions is responsible for the purple colour of amethyst?

A Cu2+

B Fe2+

C Mn3+

D Ni2+ C

43 Which of the following solids dissolves in water to form a colourless solution?

A CrCl3B CuCl2C FeCl3D ZnCl2 D

44 The table below shows the colours of the aqueous solutions of three ionic compounds:

Compound Colour of aqueous solution

WZ blue

XY orange

XZ colourless

Which of the following combinations about the colours of the ions involved is most likely to be correct?

W2+(aq) X2+(aq) Y2–(aq) Z2–(aq)

A Blue orange orange blueB Blue colourless orange colourlessC Colourless colourless colourless colourlessD Colourless orange colourless blue

B

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45 A drop of potassium permanganate solution is placed in the centre of the moistened filter paper. A d.c. power supply is then applied. Within a few minutes, a coloured patch develops near the positive electrode.

What is the colour of the patch?

A BlueB BrownC OrangeD Purple D

46 Element X forms a compound having the chemical formula K2X2O7. X could be

A Cr.B F.C Mg.D S. A

47 How many elements does ammonium sulphate consist of?

A 3B 4C 5D 6 B

48 Rubidium (Rb) is in the same group as sodium. What is the chemical formula of rubidium carbonate?

A RbCO3

B Rb(CO3)2

C Rb2CO3

D Rb3(CO3)2 C

49 The chemical formula of calcium phosphate is

A Ca(PO4)2.B Ca(PO4)3.C Ca2(PO4)3.D Ca3(PO4)2. D

50 M is an element in the third period of the periodic table. M forms a sulphate with the chemical formula M2(SO4)3. The chemical formula of the chloride of M is

A MCl2.B MCl3.C M2Cl.D M2Cl3. B

51 The chemical formula of thorium hydroxide is Th(OH)4. The chemical formula of thorium permanganate is likely to be

A ThMnO4.B Th(MnO4)2.C Th4MnO4.D Th(MnO4)4. D

52 Strontium (Sr) belongs to Group II of the periodic table. Which of the following statements concerning strontium is correct?

A Strontium is an alkali metal.B Strontium is less reactive than calcium.C The chemical formula of strontium chloride is

SrCl.D The density of strontium is higher than that

of sodium. D

53 Astatine (At) is a Group VII element. Which of the following statements concerning astatine is correct?

A Astatine is a solid at room temperature and pressure.

B Astatine is more reactive than chlorine.C Astatine is in Period 4 of the periodic table.D The formula of the compound formed between

astatine and calcium is Ca2At. A

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54 Element X can form a cation X+ with an electronic arrangement 2,8. Which of the following statements concerning X is correct?

A It is a gas at room temperature and pressure.

B It is in Period 2 of the periodic table.C It reacts vigorously with water.D It reacts with oxygen to form a compound

with the chemical formula XO2. C

55 Which of the following pairs of elements will combine to form ionic compound(s)?

(1) Calcium and fluorine(2) Neon and nitrogen(3) Potassium and sodium


56 Element X can form a cation X2+ with an electronic arrangement 2,8,8. Which of the following statements concerning X are correct?

(1) It can react with hydrogen to form a compound with the chemical formula XH2.

(2) It is in Period 3 of the periodic table.(3) It burns with a brick-red flame.


57 Caesium (Cs) belongs to Group I of the periodic table. Which of the following statements concerning caesium is / are correct?

(1) It reacts with water vigorously.(2) It has a high density.(3) The chemical formula of caesium hydroxide

is Cs(OH)2.


58 Rubidium (Rb) is a Group I element below potassium in the periodic table. Which of the following statements about rubidium are correct?

(1) Its oxide is a crystalline solid.(2) Metallic bonding exists in it.(3) The chemical formula of its sulphate is

Rb2SO4.


59 Barium (Ba) is a Group II element below calcium in the periodic table. Which of the following statements concerning barium are correct?

(1) It forms a stable ion carrying 2 positive charges.

(2) It is less reactive than calcium.(3) It forms a sulphide with the chemical

formula BaS.


60 Strontium (Sr) is a Group II element. Which of the following statements concerning strontium carbonate are correct?

(1) Its chemical formula is SrCO3.(2) It conducts electricity in solid state.(3) It is insoluble in water.


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61 The atomic number of element X is 7. Which of the following statements concerning X are correct?

(1) X is a gas at room temperature and pressure.

(2) X is in Period 3 of the periodic table.(3) X reacts with magnesium to form a

compound with the chemical formula Mg3X2.


62 An ionic compound has the chemical formula X2Y where X and Y represent the cation and anion respectively. If both X and Y have the same electronic arrangement, the compound could be

(1) lithium oxide.(2) potassium sulphide.(3) sodium oxide.


63 Which of the following ions are green in colour?

(1) Cr3+(aq)(2) Ni2+(aq)(3) MnO4

–(aq)


64 Consider the following experiment:

Which of the following statements concerning the experiment are correct?

(1) A green colour gradually develops near electrode X.

(2) Gas bubbles are evolved at electrode Y.(3) The experiment can be used to show that

ions migrate towards oppositely charged electrodes.


65 Which of the following statements about the

metallic bonding in a solid are correct?

(1) The solid contains a regular arrangement of positive ions.

(2) Outermost shell electrons of atoms are delocalized throughout the solid.

(3) This type of bonding exists in some ionic compounds.


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66 An oxide ion is very stable. An oxide ion has an electronic arrangement A

similar to that of a noble gas atom.

67 Atoms of helium and neon have 8 outermost Helium and neon are noble gases. C

shell electrons.

68 Magnesium is in Period 2 of the periodic table. Atoms of magnesium form ions carrying two C

positive charges.

69 Element X (atomic number = 20) reacts Each atom of X loses two electrons and each A

with element Y (atomic number = 7) to form atom of Y accepts three electrons to form a an ionic compound. compound with the chemical formula X3Y2.

70 A metal M which forms a chloride MCl3 must Only metals in Group III of the periodic table D

belong to Group III of the periodic table. form ions with three positive charges.

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Unit 8 Covalent bonds

Fill in the blanks

1 A covalent bond is formed when one or

more pairs of outermost shell electrons are shared

between two atoms.

2 The pair of electrons shared between two atoms

is called bond pair electrons.

3 The pair of electrons in the outermost shell of an

atom that is not involved in bonding is called

lone pair electrons.

4 Each hyd rogen mo lecu l e cons i s t s o f

two hydrogen atoms. Hydrogen forms

diatomic molecules.

5 A molecule which consists of one atom only is

called a monoatomic molecule.

6 In a hydrogen chloride molecule, the hydrogen

atom contributes one electron(s) for

bonding.

7 In an ammonia molecule, the nitrogen atom

has three bond pair(s) and one lone

pair(s) of electrons.

8 In a PCl3 molecule, the phosphorus atom

contributes three electron(s) for sharing.

9 A dative covalent bond is a covalent bond

in which the bond pair electrons are provided by

the same atom.

10 When an ammonia molecule and a hydrogen

ion combine to form an ammonium ion,

t h e n i t ro g e n a t o m s u p p l i e s i t s

lone pair electrons to the hydrogen ion.

True or false


11 In a molecule, the pair of electrons in T

the outermost shell of an atom that is not involved in bonding is called lone pair electrons.

12 Nitrogen exists as triatomic molecules. F

13 Carbon combines with silicon to form a T

covalent compound.

14 Neon and nitrogen combine to form a F

covalent compound.

15 The total number of electrons in a water F

molecule is 8.

16 In a SiCl4 molecule, the silicon atom T

contributes 4 electrons for bonding.

17 Iodine and oxygen have the same T

bonding type.

18 Hydrogen chloride and siliver chloride F have the same bonding type.

19 Phosphorus combines with hydrogen to F

form a compound with the chemical formula PH2.

20 Covalent bonds exist in ammonium T chloride.

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21 Element X (atomic number = 7) exists as molecules X2. Which of the following is the electron diagram of a molecule of X?


A

B

C

D

D

22 An element exists as diatomic molecules. The atomic number of the element could be

A 9.B 10.C 11.D 13. A

23 Which of the following pairs of elements will combine to form a covalent compound?

A Lead and bromineB Potassium and chlorineC Sodium and hydrogenD Sulphur and oxygen D

24 Which of the following pairs of elements will combine to form a covalent compound?

A Lithium and nitrogenB Mercury and fluorineC Neon and nitrogenD Fluorine and chlorine D

25 Consider the atomic numbers of four elements.

Element a b c d


Which of the following pairs of elements will combine to form a covalent compound?

A a and cB a and dC b and cD b and d C

26 The following diagram represents the particles in an element.

In which group of the periodic table is this element likely to be found?

A IIB IIIC IVD V D

27 Which of the following diagrams best represents the electron diagram of a compound formed between nitrogen and fluorine?


A

B

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C

D

C

28 Which of the following electron diagrams is correct?


A

B

C

D

D

29 Which of the following substances exists as atoms at room temperature and pressure?

A AmmoniaB HydrogenC NeonD Nitrogen C

30 The atomic number of an element X is 16. The chemical formula of the compound formed between chlorine and X is

A XCl.B XCl2.C X2Cl.D X2Cl3. B

31 The electron diagram of the compound formed between elements X and Y is shown below:


How many outermost shell electrons are there in an atom of X?

A 2B 4C 6D 8 C

32 The electron diagram of a compound formed between elements X and Y is shown below:


Which of the following combinations concerning X and Y is correct?

X Y

A Carbon sulphurB Silicon oxygenC Oxygen lithiumD Oxygen fluorine D

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33 The electron diagram of a compound formed from element X and hydrogen is shown below:


How many electrons are there in the outermost shell of an atom of X?

A 3B 4C 5D 6 C

34 Which of the following molecules contains three pairs of bond pair electrons?

A C2H4

B CO2

C H2SD PCl3 D

35 Which of the following molecules has two pairs of lone pair electrons on the underlined atom?

A CH4

B HCNC NH3

D SCl2 D

36 Elements X and Y have 5 and 7 outermost shell electrons in their atoms respectively. Which of the following combinations concerning the compound they form is correct?

Chemical formula Type of bond

A XY3 covalentB X3Y covalentC X3Y ionicD XY3 ionic A

37 Element X can form an anion X3– with an electronic arrangement 2,8. Which of the following statements concerning X is correct?

A It is in Group III of the periodic table.B It is a solid at room temperature and

pressure.C It exists as diatomic molecules.D It can react with fluorine to form

an ionic compound. C

38 Which of the following electron diagrams is correct?


A

C

B

D

D

39 In which of the following groups of substances there exists a difference in bonding type among the substances?

A Aluminium, mercury, sodiumB Calcium chloride, hydrogen chloride, silver

chlorideC Carbon dioxide, nitrogen, oxygenD Iodine, methane, sulphur dioxide B

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40 X is an element in the third period of the periodic table. The chemical formula of the compound formed between aluminium and X is Al2X3. Which of the following electron diagrams best represents the compound formed between X and hydrogen?


A

B

C

D

H X

H

H

H X

H

H

H

H X

H X

H

C

41 The electron diagram of a compound formed between an element X and chlorine is shown below.


What would be the chemical formula of the compound formed between X and calcium?

A CaXB CaX2

C Ca2X3

D Ca3X2 D

42 Consider the elements from lithium to fluorine in the second period of the periodic table. Which of the following statements is correct?

A They show a gradual change from having metallic property to having non-metallic property.

B They show a gradual increase in the number of occupied electron shells in their atoms.

C They show a gradual decrease in melting point.

D Their oxides change from covalent to ionic.

A

43 Which of the following diagrams best represents the arrangement of particles in a metal?

A

B

C

D

D

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44 Consider the following table:

ElementAtomicnumber

Relativeatomic mass

X 9 19.0

Y 13 27.0

The formula mass of the compound formed between X and Y is

A 40.0.B 84.0.C 100.0.D 111.0. B

45 Consider the following table:

ElementAtomicnumber

Relativeatomic mass

X 6 12.0

Y 16 32.1

The relative molecular mass of the compound formed between X and Y is

A 38.1.B 44.1.C 56.1.D 76.2. D

46 Which of the following elements can react together to form a covalent compound?

(1) Magnesium(2) Phosphorus(3) Oxygen(4) Helium

A (1) and (2) onlyB (1) and (4) onlyC (2) and (3) onlyD (3) and (4) only C

47 A portion of the periodic table is shown below.

Which of the following pairs of elements will form covalent compound(s) upon combination?

(1) a and f(2) b and d(3) c and e


48 Which of the following molecules have single covalent bonds only?

(1) CH4

(2) CO2

(3) H2O


49 Which of the following molecules contain multiple bond(s)?

(1) CO2

(2) N2

(3) HCN


50 Which of the following statements concerning chlorine and bromine are correct?

(1) They form ions with 1 negative charge.(2) They exist as diatomic molecules.(3) They can react with sodium sulphite

solution.

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51 Which of the following statements concerning a methane molecule is / are correct?

(1) The number of bonding electrons contributed by each hydrogen atom in the molecule is 2.

(2) The number of bonding electrons contributed by the carbon atom in the molecule is 4.

(3) The total number of electrons in the molecule is 8.


52 Which of the following electron diagrams are correct?

(1)

(2)

(3)



53 X and Y are two different elements. The electron diagram of a compound formed between X and Y is shown below:


Which of the following statement is / are correct?


(2) There are 8 electrons in the outermost shell of an atom of Y.

(3) Each atom of X in the above compound has 4 lone pairs of electrons.


54 X, Y and Z are three different elements. The electron diagram (showing electrons in the outermost shells only) of the compound formed by X, Y and Z is shown below:

Which of the following statments are correct?

(1) There is 1 electron in the outermost shell of an atom of X.


(3) There are 7 electrons in the outermost shell of an atom of Z.


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55 X, Y and Z are three different elements. The electron diagram (showing electrons in the outermost shells only) of the compound formed by X, Y and Z is shown below:

Which of the following statments are correct?



(3) There are 7 electrons in the outermost shell of an atom of Z.


56 Which of the following pairs of elements can form a compound with the chemical formula XY2?

X Y

(1) Carbon oxygen(2) Lead chlorine(3) Lithium oxygen


57 Which of the following bonds exist in ammonium nitrate?

(1) Covalent bond(2) Ionic bond(3) Metallic bond



Element X Y Z

Atomic number 9 12 16

Which of the following statements concerning the elements are correct?

(1) X and Y react to g ive an ionic compound.

(2) X and Z form a compound by electron sharing.

(3) Y and Z react to form a compound with the chemical formula YZ.


59 Which of the following statements concerning elements in the third period of the periodic table are correct?

(1) S o d i u m i s m o re r e a c t i v e t h a n magnesium.

(2) Phosphorus and chlorine will combine to form a covalent compound.

(3) The compound formed between silicon and chlorine has the chemical formula SiCl4.


60 The atomic numbers of elements X and Y are smaller than 20. X and Y belong to Group IV and VI of the periodic table respectively. Which of the following statements are correct?

(1) X tends to form an ion carrying 2 negative charges.

(2) Y is a non-metal.(3) X and Y combine to form a covalent

compound.


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61 Bromine and chlorine belong to the same group Both bromine and chloride exist as diatomic B

of the periodic table. molecules.

62 Neon and nitrogen combine to form a covalent Neon and nitrogen are non-metals. C

compound.

63 Phosphorus forms a covalent compound with Phosphorus and chlorine belong to the same B

chlorine. period of the periodic table.

64 When hydrogen combines with chlorine, an During the reaction, every electron released D

ionic compound is formed. by a hydrogen atom is accepted by a chlorine atom.

65 Calcium carbonate is a covalent compound. Covalent bonds exist in calcium carbonate. C

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Unit 9 Relating the properties of substances to structures and bonding

Fill in the blanks

1 Sod ium ch lo r ide has a g iant ion ic

structure.

2 Diamond has a giant covalent structure.

3 Iodine has a simple molecular strcuture.

4 Magnesium has a giant metallic structure.

5 Ionic compounds are usually soluble in water

but insoluble in non-aqueous solvents.

6 Molten ionic compounds can conduct electricity

because they contain mobile ions.

7 Allotropes are two (or more) forms of the

same element in which the atoms or molecules

are arranged in different ways.

8 In a quartz crystal, each silicon atom is joined

to four oxygen atoms by covalent

bonds, while each oxygen atom is joined

to two silicon atoms.

9 In graphite, the cabon atoms are arranged

in flat layers. Within each layer, each carbon

atom is joined to three carbon atoms

by covalent bonds. Van der Waals’

forces exist between the layers.

10 Substances with simple molecular structures are

usually slightly soluble or insoluble in water

but very soluble in non-aqueous solvents.

11 Bromine has a simple molecular structure.

The atoms in each molecule are held together by

a covalent bond . The separate molecules are

held together by van der Waals’ forces .

12 Metals are good conductors of electricity due to

the movement of mobile electrons .

True or false


13 Quartz and graphite are allotropes. F

14 The strcuture of silicon is similar to that T

of diamond.

15 Silicon carbide (SiC) has a simple F

molecular structure.

16 Silane (SiH4) has a simple molecular T

structure.

17 Carbon disulphide (CS2) has a giant F covalent structure.

18 Sugar has a simple molecular structure. T

19 Copper has a giant metallic structure. T

20 Ionic compounds conduct electricity in F solid state.

21 Sodium chloride is hard due to the strong T ionic bonds between the ions.

22 The melting point of diamond is higher F than that of graphite.

23 In quartz, van der Waals’ forces hold the F atoms together.

24 Graphite has a slippery feel. T

25 Diamond is harder than graphite. T

26 Graphite is used as electrodes in dry T

cells.

27 In dry ice, the carbon dioxide molecules F

are held together by covalent bonds.

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28 In iodine, the atoms in each molecule F are held together by van der Waals’ forces.

29 Iodine is very soluble in water. F

30 Carbon dioxide and silicon dioxide have F similar physical properties.

31 The melting point of hydrogen chloride is T lower than that of potassium chloride.

32 Silver is a good conductor of electricity T due to the movement of mobile electrons.


33 Which of the following terms correctly describes the structure of potassium bromide?

A Giant covalent structureB Giant ionic structureC Giant metallic structureD Simple molecular structure B

34 Which of the following diagrams best represents the giant structure of a sodium chloride crystal? (In these diagrams, represents a Na+ ion and

represents a Cl– ion.)

A B

C D

A

35 Which of the following substances is an electrolyte?

A ArgonB PotassiumC Potassium fluorideD Tetrachloromethane C

36 Solid zinc chloride CANNOT conduct electricity because

A it contains molecules.B it is a non-electrolyte.C it is a covalent compound.D it does not contain mobile ions. D

37 Ionic compounds have high melting points because

A the ions are packed in layers.B they are insoluble in water.C ionic bonds hold the ions together.D they contain mobile ions. C

38 Magnesium oxide is used to line industrial furnaces because it has a very high melting point.

Which type of bond needs to be broken for magnesium oxide to melt?

A Covalent bondB Dative covalent bondC Ionic bondD Metallic bond C

39 Which of the following chlorides has the highest melting point?

A HClB KClC SCl2D PCl3 B

40 Which of the following substances is the hardest?

A DiamondB SteelC GraphiteD Magnesium oxide A

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41 Which of the following correctly describes the structure of silicon dioxide?

A Simple molecular structureB Giant ionic structureC Giant covalent structureD Giant metallic structure C

42 Quartz has a very high melting point because

A it is a covalent compound.B it has a giant covalent structure.C its atoms are held together by strong ionic

bonds.D it contains molecules held together by strong

forces. B

43 Which of the following substances is the most stable in moist air?

A CaB NaC SiO2

D SO2 C

44 Graphite can be used as a lubricant. This is because graphite has

A mobile ions.B delocalized electrons.C covalent bonds between atoms in the

layers.D van der Waals’ forces between the layers of

atoms. D

45 Which of the following correctly describes the structure of dry ice?

A Giant covalent structureB Giant ionic structureC Giant metallic structureD Simple molecular structure D

46 Which of the following substances has a simple molecular structure?

A DiamondB MercuryC NitrogenD Quartz C

47 Which of the following substances consists of separate molecules?

A Calcium oxideB GraphiteC IodineD Sodium C

48 Which of the following oxides has a simple molecular structure?

A MgOB Al2O3

C SiO2

D Cl2O D

49 In which of the following substances do van der Waals’ forces exist?

A QuicklimeB SiliconC Solid carbon dioxideD Solid ammonium chloride C

50 Bromine is a liquid at room temperature and pressure because

A bromine has a giant covalent structure.B bromine molecules are diatomic.C bromine molecules are held together by weak

intermolecular forces only.D bromine atoms within the molecules are held

by strong covalent bonds. C

51 A substance melts at –10 °C and boils at 58 °C. Which of the following statements concerning the substance is probably correct?

A It has a simple molecular structure.B It is insoluble in non-aqueous solvents.C It is a gas at room temperature and

pressure.D It conducts electricity in solid state. A

52 Which of the following substances is insoluble in water but soluble in non-aqueous solvents?

A Common saltB SugarC SulphurD Sodium nitrate C

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53 An element X combines with chlorine to form a compound with a simple molecular structure. The atomic number of X could be

A 10.B 11.C 16.D 20. C

54 The atomic number of element X is 15. It has only one isotope with a mass number 31. Which of the following statements concerning X is correct?

A X is a gas at room temperature and pressure.

B The chemical forumla of the hydride of X is XH3.

C There are 16 electrons in an atom of X.D Covalent bonds hold the molecules of X

together. B


Element X Y Z


Which of the following statements concerning X, Y and Z is correct?

A X and Z combine to form a covalent compound.

B Y has a simple molecular structure.C Z exists as a liquid at room conditions.D A metal cyclinder containing X should bear

the following hazard warning label.

A


Element X Y Z


Which of the following statements concerning X, Y and Z is correct?

A X has a high melting point.B Y has a giant covalent structure.C Z gives an apple green flame in flame test.D X and Z combine to form a compound with

a simple molecular structure. B

57 Consider the following substances:

carbon dioxide (CO2), silicon dioxide (SiO2) and sodium oxide (Na2O)

The ascending order of the melting points of these substances is

A CO2 < Na2O < SiO2

B CO2 < SiO2 < Na2OC SiO2 < CO2 < Na2OD Na2O < SiO2 < CO2 A

Directions: Questions 58 – 59 refer to the following information of four elements:

ElementMelting

point (°C)Boiling

point (°C)

Electrical conductivity in

molten / liquid state

W 650 1 120 good conductor

X 1 610 2 230 non-conductor

Y –39 357 good conductor

Z 113 445 non-conductor

58 Which of the fo l lowing statements i s INCORRECT?

A W is a brittle solid.B X has a giant covalent structure.C Y is a good conductor of heat.D Z is a non-metal. A

59 Element Y is likely to be

A magnesium.B mercury.C silicon.D sodium. B

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SubstanceMelting

point (°C)Electrical

conductivitySolubility in

water

W –7 non-conducting slightly soluble

X 46 non-conducting insoluble

Y 420 conducting insoluble

Z 782 non-conducting soluble

Which of the substances exists as a simple molecular solid at room temperature?

A WB XC YD Z B

61 A Group I element X forms a compound with a Group VII element Y. Which of the following statements concerning the compound is INCORRECT?

A The compound has a giant ionic structure.B The compound is a liquid at room temperature

and pressure.C The chemical formula of the compound is

XY.D The compound conducts electricity in molten

state. B

62 The table below shows the information of two elements.

Element Electronic arrangement of atom

X 2,8,5

Y 2,7

Which of the following statements concerning the compound Z formed between X and Y is correct?

A The bonds in Z are formed by electron transfer.

B Z has a giant structure.C Z has a low melting point.D The chemical formula of Z is XY4. C

63 X and Y are elements. The melting points of their chlorides are given below:

Element Melting point (°C)

Chloride of X –82

Chloride of Y 808


A Both X and Y are non-metals.B The chloride of X is an ionic compound.C The chloride of Y is a solid at room temperature

and pressure.D The chloride of Y conducts electricity in solid

state. C

64 Which of the following substances can conduct electricity in both solid and liquid states?

A Carbon dioxideB DiamondC MagnesiumD Sodium chloride C

65 Copper has a high melting point because

A it is ductile.B it contains mobile electrons.C it is malleable.D metallic bonds hold its particles together. D

66 Why does a silver wire conduct electricity when it is connected to a battery?

A Mobile electrons in the metal move.B Silver ions move towards the positive terminal

of the battery.C The silver atoms become ions.D The structure of silver breaks down. A

67 The table below shows the electrical conductivity of four substances W, X, Y and Z.

Substance Solid stateMolten state

Aqueous solution

W ✘ ✘ ✘

X ✘ ✔ ✔

Y ✘ ✘ ✔

Z ✔ ✔(insoluble in

water)

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(In the table, ✔ and ✘ represent ‘can conduct electricity’ and ‘cannot conduct electricity’ respectively.)

Which of the substances is likely to be a metal?

A WB XC YD Z D

Directions: Questions 68 – 69 refer to the melting points and boiling points of four substances at 1 atm pressure as listed in the table below:


Bromine –7 59

Chlorine –101 –35

Oxygen –218 –183

Hydrogen bromide

–88 –67

68 Which substance exists as a liquid at –50 °C and 1 atm pressure?

A BromineB ChlorineC OxygenD Hydrogen bromide B

69 Which of the following chemical bonds / attractive forces exist(s) in all four substances at 25 °C and 1 atm pressure?

(1) Van der Waals’ forces(2) Ionic bond(3) Covalent bond

A (1) onlyB (2) onlyC (1) and (3) onlyD (2) and (3) only C

70 Which of the following substances has / have giant structure(s)?

(1) Oxygen(2) Potassium oxide(3) Silicon dioxide


71 Which of the following substances can conduct electricity?

(1) Graphite(2) Molten zinc chloride(3) Magnesium sulphate solution


72 The structure of silicon carbide is shown below:

Which of the following statements concerning silicon carbide are correct?

(1) Its chemical formula is SiC2.(2) It has a high melting point.(3) It is insoluble in water.


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73 Germanium is a Group IV element below silicon in the periodic table. Which of the following statements concerning germanium is / are probably correct?

(1) It is a metalloid.(2) It has a high melting point.(3) I ts f luor ide has a giant covalent

structure.


74 A certain form of solid carbon is composed of C60 molecules. Each C60 molecule is formed by 60 carbon atoms bonded together like a football as shown in the diagram below:

Which of the following statements is / are correct?

(1) The solid is insoluble in water.(2) The solid is harder than diamond.(3) The melting point of the solid is higher

than that of graphite.


75 Selenium (Se) is a group VI element of the periodic table. Which of the following statements concerning selenium are correct?

(1) Selenium forms a covalent hydride.(2) The chloride of selenium is a solid with a

network structure.(3) Selenium forms Se2– ions when reacted

with Group I elements.


76 Which of the following properties of graphite is / are evidence(s) to support that covalent bonds are strong?

(1) It is slippery.(2) It has a high melting point.(3) It can conduct electricity.


77 Element X exists as diatomic molecules. Solid X has a very low melting point. It is insoluble in water but soluble in non-aqueous solvents. X does not conduct electricity. From these information it can be deduced that

(1) X has a simple molecular structure.(2) the attractive forces between molecules

of X are weak.(3) the attractive forces between the atoms

of X are weak.


78 Refer to the information of some chlorides shown in the following table.

Chloride Melting point (°C) Boiling point (°C)

NaCl 808 1 465

MgCl2 712 1 418

SiCl4 –68 57

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Which of the following statements are correct?

(1) Silicon tetrachloride is a liquid at room temperature and pressure.

(2) Magnesium chloride has a giant ionic structure.

(3) Both sodium chloride and magnesium chloride conduct electricity when heated to 750 °C.


79 The following table shows the melting points of three compounds.

Compound Melting point (°C)

NaH 800

SiH4 –185

H2S –85

Which of the following statements can be deduced from the above data?

(1) NaH is a solid at 700 °C.(2) SiH4 has a giant covalent structure.(3) H2S is a solid at room temperature and

pressure.


80 X has a very high melting point and does NOT conduct electricity at room temperature. It may have a

(1) giant covalent structure.(2) giant ionic structure.(3) giant metallic structure.


81 The atomic numbers of two elements X and Y are 19 and 16 respectively. Which of the following statements concerning the compound formed between X and Y are correct?

(1) Its chemical formula is X2Y.(2) It is very soluble in non-aqueous

solvents.(3) It conducts electr ic ity in aqueous

solution.


82 The atomic numbers of elements X and Y are 8 and 9 respectively. They combine to form a compound Z. Which of the following statements concerning Z is / are correct?

(1) It has a giant covalent structure.(2) Its chemical formula is XY2.(3) It is very soluble in water.


83 Metal X reacts with oxygen to form a compound with a chemical formula X2O3. Which of the following statements are correct?

(1) The chemical formula of the chloride of X is XCl3.

(2) X2O3 has a giant ionic structure.(3) X2O3 conducts electricity in molten state.


44

Part A

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Element Atomic numberRelative

atomic mass

P 9 19.0

Q 17 35.5

Elements P and Q combine to form a compound X. Which of the following statements about X are correct?

(1) X is formed by electron sharing.(2) The relative molecular mass of X is

54.5.(3) X is a solid at room temperature and

pressure.




atomic mass

P 7 14.0

Q 12 24.3


(1) X is formed by electron transfer.(2) X is a solid at room temperature and

pressure.(3) The formula mass of X is 90.6.





86 All ionic compounds are soluble in water. The attractive forces between water molecules D

are similar to ionic bonds.

87 Potassium chloride has a high melting point. The ionic bonds in potassium chloride are A

strong.

88 Iodine is slightly soluble in non-aqueous solvents. The attractive forces between iodine molecules D

are much stronger than those between molecules of iodine and non-aqueous solvents.

89 Covalent bonds are weak. Many covalent compounds are gases, liquids C

or solids with low melting points.

45

Part B


90 Both diamond and graphite conduct electricity. Diamond and graphite are allotropes of C

carbon.

91 The solubility of calcium carbonate in water is Calcium carbonate is an ionic compound while C

much greater than that of ammonia. ammonia is a covalent compound.

92 The aqueous solution of sugar conducts Sugar reacts with water to form ions. D

electricity.

93 When iodine sublimes, it absorbs heat. Large amount of heat is required to break B

the strong covalent bonds between iodine atoms.

94 Carbon dioxide and silicon dioxide have similar Both carbon and silicon belong to Group IV C physical properties. of the periodic table.

95 Metals are good conductors of heat. Metals contain mobile electrons. A

Part B Topic-based exercise


1 The following ideas were those underlying John Dalton’s atomic theory, published in 1803.

Which idea is known to be correct?

A Atoms are indivisible.B Atoms are very small.C Atoms of an element are identical.D Atoms of one element always differ in mass

from those of another element. B

2 The melting and boiling points of three substances X, Y and Z are given in the table below:

Substance X Y Z

Melting point (°C) –146 –210 –108

Boiling point (°C) –80 –105 –45

A mixture of the three substances at –110 °C is allowed to warm up gradually to –70 °C. Which of the descriptions is correct?

A Y exists in the liquid state.B Z exists in the liquid state.C X and Y exists in the liquid state.D X, Y and Z exist in the gaseous state. B

3 The representation 1399K indicates that this atom

has

A 19 protons, 19 neutrons and 20 electrons.B 19 protons, 20 neutrons and 19 electrons.C 20 protons, 20 neutrons and 19 electrons.D 20 protons, 19 neutrons and 20 electrons.

B

4 In which species are the numbers of electrons and neutrons equal?

A 49Be

B 1231Na+

C 1273Al

D 1357Cl– D

46

Part B

5 M is an element. The M2+ ion possesses 34 neutrons and 27 electrons. What is M?

A CoB CuC GaD Se B

6 A sample of krypton consists of 45.0% 84Kr and 55.0% 86Kr. The relative atomic mass of krypton is

A 84.9.B 85.0.C 85.1.D 85.5. C

7 Iodine (relative atomic mass = 126.9) consists of a mixture of two isotopes: 126I and 127I. What is the relative abundance of 127I in iodine?

A 10.0%B 30.0%C 70.0%D 90.0% D

8 A and B are two halogens. If the atomic number of A is x, then the atomic number of B could be

A x – 4.B x – 10.C x + 6.D x + 18. D

9 Which of the following pairs of atoms have similar chemical properties?

A 24X and 1

200Y

B 162X and 1

242Y

C 1231X and 1

357Y

D 1408X and 2

400Y A

10 Which of the following pairs of elements in Groups I and VII of the periodic table would react with each other most vigorously?

Group I Group VII

A Rb ClB Rb BrC Na ClD Na Br A

11 Which of the following statements concerning the elements in Group 0 is INCORRECT?

A They can be found in the air.B Their boiling points increase down the

group.C They exist in gaseous state at room temperature

and pressure.D Their atoms have the same number of

outermost shell electrons. D

12 Consider the following atoms:

Atom W X Y Z


Number of neutrons 7 18 8 20

Which of the fo l lowing statements i s INCORRECT?

A W and Y belong to the same period.B X and Z have similar chemical properties but

different physical properties.C W is a gas at room temperature and

pressure.D X is a non-metal. B

13 The number of neutrons in the 3794Se2– ion is

A 32.B 34.C 36.D 45. D

14 Cerium (Ce) forms the 15840Ce3+ ion. The number

of electrons in this ion is

A 55.B 58.C 61.D 140. A

15 When an atom of a Group I element X forms an ion,

A its mass number increases.B the charge of the nucleus increases.C Its atomic number decreases.D the number of occupied electron shells

decreases. D

47

Part B

16 X is an element and the ion X– has an electronic arrangement 2,8,8. Which of the following statements concerning X is correct?

A X is a halogen.B X is a transition metal.C X is a Group 0 element.D X is a Period 4 element. A

17 Which of the following compounds contains ions which have the same electronic arrangement?

A Na2OB Li3NC CaOD SrCl2 A

18 In the circuit shown below, the bulb does NOT light up.

Which of the following changes would cause the bulb to light up?

A Add more solid copper(II) chloride to the beaker.

B Add water to dissolve the solid copper(II) chloride.

C Replace the carbon electrodes with copper electrodes.

D Reverse the connections to the electrodes.

B

19 Which of the following diagrams best represents the arrangement of particles in a sample of chlorine at room temperature and pressure?

A

B

D

C

C

20 The electron diagram of a compound formed between magnesium and element X is shown below.

What would be the chemical formula of the compound formed between X and chlorine?

A XCl2B XCl3C X2Cl3D X3Cl2 B

21 Element E forms a sulphate with the chemical formula E2(SO4)3. Element Z forms a molecular hydride with the chemical formula H2Z. The chemical formula of the compound formed from E and Z is likely to be

A EZB EZ2

C E2Z3

D E3Z2 C

48

Part B

22 X, Y and Z are three different elements. A compound formed between these elements has the following electronic structure:


How many electrons are there in the outermost shell of an atom of Y?

A 4B 5C 6D 7 A

23 Element X forms an anion X3– with an electronic arrangement 2,8. Which of the following statements concerning X is correct?

A It is in Group III of the periodic table.B It is a solid at room temperature and

pressure.C It exists as diatomic molecules.D It can react with neon to form a covalent

compound. C

24

A colour moved towards the right in the above set-up. The coloured crystal on the filter paper could be

A copper(II) sulphate.B potassium chromate.C sodium permanganate.D zinc sulphate. A

25 The table below shows the colour of the aqueous solutions of three ionic compounds.

Compound Colour of aqueous solution

WX green

YX colourless

YZ purple

Which of the following combinations about the colours of the ions involved is most likely to be correct?

W2+(aq) X2–(aq) Y2+(aq) Z2–(aq)

A Colourless green purple colourlessB Colourless colourless colourless colourlessC Green colourless colourless purpleD Green green purple purple

C


SolidMelting

pointElectrical

conductivitySolubilityin water

W very highnon-

conductinginsoluble

X very lownon-

conductingsoluble

Y highnon-

conductingsoluble

Z high good insoluble

Which of the following solids is likely to be zinc chloride?

A WB XC YD Z C

27 Which of the following solids has a low melting point and a high electrical conductivity?

A IodineB PotassiumC Potassium fluorideD Silicon dioxide B

49

Part B

28 Which of the following statements concerning carbon dioxide is correct?

A Solid carbon dioxide has a covalent network structure.

B Carbon dioxide is used to fill weather balloons.

C Carbon dioxide dissolves in water to give an acidic solution.

D Carbon dioxide and silicon dioxide have similar physical properties.

C

29 Which of the following substances has the highest melting point?

A MethaneB SodiumC SiliconD Sulphur C

30 Which of the following statements concerning van der Waals’ forces is correct?

A They exist in diamond.B They exist in limestone.C They exist in dry ice.D They exist in solid ammonium nitrate. C

31 In which of the following groups of substances there exists a difference in bonding type among the substances?

A Barium fluoride, magnesium fluoride, potassium fluoride

B Carbon monoxide, sulphur dioxide, methaneC Chromium, magnesium, nickelD Boron trichloride, silicon tetrachloride, sodium

chloride. D

32 Which of the following chlorides has the lowest boiling point?

A HClB KClC AlCl3D CCl4 A

33 An element (melting point above 3 000 °C) forms an oxide which is a gas at room temperature.What type of structure is likely to be present in the element?

A IonicB MetallicC Covalent molecularD Covalent network D

34 Which of the following chlorides is most likely to be soluble in tetrachloromethane, CCl4?

A Barium chlorideB Caesium chlorideC Calcium chlorideD Phosphorus trichloride D

35 The physical properties of three substances X, Y and Z are shown below.

SubstanceMelting

point (°C)Boiling

point (°C)

Electrical conductivity

in solid state

in moltenstate

X 801 1 413 poor good

Y 2 852 3 600 poor good

Z 3 550 4 827 good not known

What could be the identities of X, Y and Z?

X Y Z

A NaF KCl FeB NaBr BaO SiO2

C NaCl MgO C(graphite)D NaBr CaO C(diamond) C

50

Part B

36 Consider the following information about four substances, W, X, Y and Z

SubstanceMelting

point (°C)Boiling

point (°C)

Electrical conductivity at room

temperature

W 71 375 poor conductor

X 98 890 good conductor

Y –130 36 poor conductor

Z –138 –0.5 poor conductor

Which substance has a simple molecular structure and is a liquid at room temperature?

A WB XC YD Z C

37 The atomic numbers of elements X and Y are 8 and 9 respectively. They combine to form a compound Z. Which of the following statements concerning Z is INCORRECT?

A Its chemical formula is XY2.B It is formed by electron sharing.C Van der Waals’ forces exist in it.D It is a crystalline solid at room temperature

and pressure. D



X 14

Y 17


A X has a simple molecular structure.B Y is a volatile liquid.C The compound formed between X and Y has

a giant covalent structure.D The compound formed between X and Y has

a low melting point. D

39 X and Y are elements. The boiling points of their oxides are given below:

Boiling point (°C)

Oxide of X –78

Oxide of Y 2 230


A X is a metal.B The oxide of X is a covalent compound.C The oxide of Y is a gas at room temperature

and pressure.D Van der Waals’ forces exist in the oxide of

Y. B

40 A gallium isotope 3681Ga can be used to detect

tumours. Which of the following statements about this gallium isotope is / are correct?

(1) It has 37 neutrons.(2) Its atomic number is 68.(3) Its chemical properties are the same as

those of other isotopes of gallium.


41 Which of the following species has (have) an octet structure in the outermost shell(s)?

(1) Li+

(2) N3–

(3) Ar


42 Which of the following statements about the periodic table are correct?

(1) The reactivity of Group II elements increases with relative atomic mass.

(2) The boiling point of Group VII increases with relative atomic mass.

(3) All elements in Group 0 exist in gaseous state at room temperature and pressure.

51

Part B


43 In moving from Group I to Group VII across the third period of the periodic table, which of the following physical properties of the elements show a gradual change?

(1) Atomic size(2) Metallic character(3) Melting point


44 The elements, sodium to chlorine, in the third period of the periodic table show a gradual change in properties. Which of the following descriptions are correct?

(1) The number of outermost shell electrons in their atoms increases.

(2) Their ability to gain electrons increases.(3) Their chlorides change from covalent to

ionic.


45 A small piece of potassium is dropped into a trough of water. A piece of red litmus paper is used to test the water after the experiment. Which of the following observations are correct?

(1) The potassium moves on the water surface with a hissing sound.

(2) The potassium burns with a lilac flame.(3) The water turns the red litmus paper

blue.


46 Which of the following properties of Group II elements increase with relative atomic mass?

(1) Atomic size(2) Melting point(3) Reactivity with water


47 Caesium (Cs) belongs to Group I of the periodic table. Caesium reacts with bromine to form a compound. Which of the following statements concerning the compound are correct?

(1) Its chemical formula is CsBr.(2) It is very soluble in non-aqueous

solvents.(3) It is a crystalline solid at room temperature

and pressure.


48 Strontium (Sr) is a Group II element. Which of the following statements concerning strontium is / are correct?

(1) Strontium does not burn in air.(2) Strontium reacts with water to liberate

hydrogen.(3) All its compounds are coloured.


49 Germanium (Ge) is a Group IV element below silicon in the periodic table. Which of the following statements concerning germanium are correct?

(1) It has a giant covalent structure.(2) Its atomic size is larger than that of

silicon.(3) Its fluoride has a chemical formula GeF4.


52

Part B

50 Which of the following statements concerning chlorine are correct?

(1) It exists as diatomic molecules.(2) It is denser than air.(3) It is used to sterilize swiming pool

water.


51 Which of the following statements concerning halogens are correct?

(1) Compounds of fluorine are added to tap water to help prevent tooth decay.

(2) Bromine is a volatile liquid.(3) Iodine can sublime.


52 Which of the following statements concerning chlorine, bromine and iodine are correct?

(1) They are all coloured substances.(2) Their reactivity decreases down the

group.(3) Van der Waals’ forces exist between their

molecules .


53 Hydrogen peroxide (H2O2) is an oxide of hydrogen. Which of the following statements concerning a hydrogen peroxide molecule is / are correct?

(1) The number of bonding electrons contributed by each hydrogen atom in the molecule is 2.

(2) The number of bonding electrons contributed by each oxygen atom in the molecule is 2.

(3) The total number of electrons in the molecule is 18.


54 Which of the following bonds or attractive forces exist in calcium carbonate?

(1) Ionic bond(2) Covalent bond(3) Van der Waals’ forces


55 Which of the following substances have giant structures?

(1) Copper(2) Nitrogen dioxide(3) Silicon dioxide


56 Consider the following information:

Attractions between Substance particles in substance

(1) Neon van der Waals’ forces(2) Zinc metallic bond(3) Magnesium chloride ionic bond

Which of the following combinations are correct?


53

Part B

57 In which of the following groups of substances do members have the same bonding type?

(1) Copper, mercury, tungsten(2) Dry ice, nitrogen dioxide, water(3) Copper(II) chloride, hydrogen chloride,

zinc chloride


58 Which of the following substances contain delocalized electrons?

(1) Graphite(2) Methane(3) Sodium


59 Which of the following properties of potassium chloride is / are evidence(s) to support that ionic bonds are strong?

(1) It can conduct electricity in molten state.

(2) It has a high melting point.(3) It is soluble in water.




atomic mass

P 7 14.0

Q 9 19.0


(1) X is formed by electron transfer.(2) The relative molecular mass of X is

71.0.(3) Van der Waals’ forces exist in X.


54

Part B




61 Isotopes of an element have the same chemical Isotopes of an element have the same number A

properties. of outermost shell electrons.

62 Argon is used to fill electric light bulbs. Argon exists as monoatomic molecules. B

63 Nitrogen is used to fill the packets of potato Nitrogen is a gas at room temperature and B

chips. pressure.

64 Aqueous solution of carbon dioxide cannot Carbon dioxide is a covalent compound. C

conduct electricity.

65 Metals are good conductors of electricity. Metals contain mobile electrons. A

66 Bromine is a good conductor of electricity. Bromine contains mobile bromine molecules. C

67 All covalent substances are insoluble in water. All covalent substances have simple molecular D

structures.

68 The boiling point of bromine is higher than that The van der Waals’ forces between bromine A

of chlorine. molecules are stronger than those between chlorine molecules.

69 The melting point of hydrogen chloride is lower Hydrogen chloride is a covalent compound B

than that of zinc chloride. while zinc chloride is an ionic compound.

70 In ammonia, the mass of hydrogen is three An ammonia molecule contains one nitrogen C

times that of nitrogen. atom and three hydrogen atoms.

55

Part B

Short questions

71 Complete the following table by (12 marks)

a) filling in the names or symbols of the elements;

b) classifying each element into metal, metalloid or non-metal.

Element Symbol Metal / Metalloid / Non-metal

Argon Ar non-metal

Carbon C non-metal

Calcium Ca metal

Fluorine F non-metal

Germanium Ge metalloid

Lithium Li metal

Magnesium Mg metal

Neon Ne non-metal

Nitrogen N non-metal

Potassium K metal

Phosphorus P non-metal

Silicon Si metalloid (0.5 x 24)

72 Complete the following table. (20 marks)

AtomAtomic number

Massnumber

SymbolNumber of

protons neutrons electrons

Oxygen 8 16 816O 8 8 8

Sodium 11 23 123

1Na 11 12 11

Aluminium 13 27 1273Al 13 14 13

Sulphur 16 32 132

6S 16 16 16

Chlorine 17 35 1357Cl 17 18 17

Potassium 19 39 1399K 19 20 19

Calcium 20 40 240

0Ca 20 20 20

Iron 26 56 256

6Fe 26 30 26 (0.5 x 40)

56

Part B

73 Look at the list of elements.

boron chlorine copper fluorine magnesium nickel nitrogen phosphorus

Answer the following questions. Choose all your answers from the list. Each element can be used once, more than once or not at all. (6 marks)

a) Write down the name of a greenish yellow gas.

chlorine (1)

b) Write down the name of an element that forms compounds that are blue in colour.

copper (1)

c) Write down the name of the element whose atom contains 15 protons.

phosphorus (1)

d) Write down the name of the element whose atom has an electronic arrangement 2,5.

nitrogen (1)

e) Write down the name of a metalloid.

boron (1)

f) Write down the name of an element that forms ions which is green in aqueous solution.

nickel (1)

74 a) Complete the following table. (20 marks)

SpeciesAtomicnumber

Massnumber

Number of Electronicarrangementprotons neutrons electrons

i) Beryllium atom 4 9 4 5 4 2,2

ii) Neon atom 10 20 10 10 10 2,8

iii) Silicon atom 14 28 14 14 14 2,8,4

iv) Phosphorus atom 15 31 15 16 15 2,8,5

v) Potassium ion 19 39 19 20 18 2,8,8

vi) Nitride ion 7 14 7 7 10 2,8

vii) Magnesium ion 12 24 12 12 10 2,8

viii) Fluoride ion 9 19 9 10 10 2,8

ix) Sodium ion 11 23 11 12 10 2,8

x) Sodium atom 11 23 11 12 11 2,8,1

(0.5 x 40)

57

Part B

b) Which species in the above table is / are negatively charged? (1 mark)

Species (vi) & (viii) / nitride ion and fluoride ion (0.5 x 2)

c) In which group of the periodic table should species (iii) be placed? Explain your answer. (2 marks)

Group IV; (1)

it has 4 electrons in its outermost shell. (1)

d) State the relationship between species (ix) and (x). (1 mark)

Species (ix) is the cation of species (x) / (ix) and (x) are the ion and atom of the same element. (1)

75 a) Write down the chemical formula for each of the following compounds. (8 marks)

Name Chemical formula

Aluminium hydroxide Al(OH)3

Ammonium dichromate (NH4)2Cr2O7

Calcium phosphate Ca3(PO4)2

Copper(II) chloride CuCl2

Iron(III) oxide Fe2O3

Magnesium hydroxide Mg(OH)2

Potassium carbonate K2CO3

Sodium sulphite Na2SO3 (1 x 8)

b) Write down the names of the following compounds. (8 marks)

Chemical formula Name

KHCO3 potassium hydrogencarbonate

Fe2(SO4)3 iron(III) sulphate

Cu(OH)2 copper(II) hydroxide

Mg3N2 magnesium nitride

Zn(NO3)2 zinc nitrate

NaS sodium sulphide

Al2O3 aluminium oxide

AgCl silver chloride (1 x 8)

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Part B

76 Complete the following table. (21 marks)

Cation Anion Compound

Name Formula Name Formula Name FormulaColour of aqueous solution

ammonium NH4+ carbonate CO3

2– ammonium carbonate (NH4)2CO3 colourless

copper(II) Cu2+ nitrate NO3– copper(II) nitrate Cu(NO3)2 blue

iron(II) Fe2+ sulphate SO42– iron(II) sulphate FeSO4 pale green

potassium K+ permanganate MnO4– potassium permanganate KMnO4 purple

nickel(II) Ni2+ chloride Cl– nickel(II) chloride NiCl2 green

aluminium Al3+ iodide I– aluminium iodide All3 colourless

chromium(III) Cr3+ chloride Cl– chromium(III) chloride CrCl3 green

sodium Na+ dichromate Cr2O72– sodium dichromate Na2Cr2O7 orange

zinc Zn2+ bromide Br– zinc bromide ZnBr2 colourless

(0.5 x 42)

77 a) Use an electron diagram to show the electron transfer when each of the following pairs of elements combine, showing electrons in the outermost shells only. (3 marks)

i) Calcium and chlorine

(1)

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Part B

ii) Magnesium and nitrogen

(1)

iii) Sodium and sulphur

(1)

b) Use an electron diagram to show the sharing of electrons when each of the following pairs of elements combine, showing electrons in the outermost shells only. (3 marks)

i) Phosphorus and chlorine

(1)

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Part B

ii) Oxygen and hydrogen

iii) Chlorine and fluorine

78 Calculate the formula masses or relative molecular masses of the following substances. (5 marks)

Substance Chemical formulaRelative atomic

mass(es)

Formula mass /relative molecular

mass

Oxygen O2 O = 16.0 32.0

Carbon dioxide CO2 C = 12.0 O = 16.0

44.0

Potassium nitrate KNO3

N = 14.0 O = 16.0 K = 39.1

101.1

Calcium hydroxide Ca(OH)2

H = 1.0 O = 16.0 Ca = 40.1

74.1

Iron(III) sulphate Fe2(SO4)3

O = 16.0 S = 32.1 Fe = 55.8

399.9(1 x 5)

79 Phosphorus and nitrogen are in Group V of the periodic table and both elements form hydrides. Phosphine, PH3, reacts to form phosphonium ions, PH4

+, in a way similar to that by which ammonia, NH3, forms ammonium ions, NH4

+.

a) Give the name of the type of bond formed when PH3 reacts with an H+ ion. (1 mark)

Dative covalent bond (1)

(1)

(1)

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Part B

b) Explain how the bond is formed. (2 marks)

The phosphorus atom (1)

supplies both bonding electrons to the hydrogen ion. (1)

80 Arrange the following substances into four groups according to their structures:

carbon dioxide, chlorine, copper, copper(II) sulphate, diamond, magnesium fluoride, nitrogen, quartz, sodium, sodium sulphide (5 marks)

Giant ionic structure

Giant covalent structure

Simple molecular structure

Gaint metallic structure

copper(II) sulphate,magnesium fluoride,sodium sulphide

diamond,quartz

carbon dioxide,chlorine,nitrogen

copper,sodium

(0.5 x 10)

81 Write down the type of forces of attraction (ionic bond / covalent bond / metallic bond / van der Waals’ forces) present in each of the following cases: (5 marks)

Forces of attraction

Between carbon atoms in diamond covalent bond

Between carbon dioxide molecules in dry ice van der Waals’ forces

Between particles in calcium nitride ionic bond

Between particles in magnesium metallic bond

Between carbon and oxygen atoms in a carbon dioxide molecule

covalent bond(1 x 5)

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Part B

82 Consider the following liquids:

molten potassium

molten sulphur

molten potassium chloride

liquid hydrogen chloride

a) Classify each of the above liquids in one of the following three ways according to its response to a direct current: (4 marks)

Non-conductorConductor, with decomposition

at the electrodesConductor, but without

decomposition

molten sulphur (1)

liquid hydrogen chloride (1)

molten potassium chloride (1) molten potassium (1)

b) For each of the above liquids which are conductors, state the particles responsible for the conduction of electricity. (2 marks)

molten potassium chloride — mobile potassium ions and chloride ions (1)

molten potassium — mobile electrons (1)

Structured questions

83 Silver occurs in nature as two isotopes: 107Ag and 109Ag. The relative abundance of these isotopes is shown below.


107Ag 55

109Ag 45

a) State the meaning of the term ‘relative atomic mass’. (2 marks)

The relative atomic mass of an element is the weighted average relative isotopic mass of all the naturally occurring

isotopes of that element (1)

on the 12C = 12.00 scale. (1)

b) Calculate the relative atomic mass of silver. (2 marks)107 x 55 + 109 x 45

100 (1)

= 107.9 (1)

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Part B

c) Is it possible to separate the isotopes of silver by chemical means? Explain your answer. (2 marks)

Isotopes of silver have the same chemical properties. (1)

Hence it is impossible to separate the isotopes of silver by chemical means. (1)

84 Silicon occurs naturally in three isotopic forms. The relative abundance of each isotope is shown in the table below:

Isotope 28Si 29Si 30Si

Relative abundance (%) ? ? 3.1

a) State the meaning of the term ’isotopes’. (2 marks)

Isotopes are different atoms of an element which have the same number of protons (1)

but a different number of neutrons. (1)

b) The relative atomic mass of silicon is 28.09. Calculate the relative abundance of the 28Si isotope. (2 marks)

Let the relative abundance of 28Si and 29Si be y% and (96.9 – y)% respectively.

28.09 =

28 x y + 29 x (96.9 – y) + 30 x 3.1100 (1)

y = 94.1 (1)

c) Suggest ONE use of silicon. (1 mark)

Making semi-conductors (1)

d) Silicon combines with carbon to form silicon carbide (SiC). The structure of silicon carbide is similar to that of diamond. Draw the three-dimensional structure of silicon carbide. (2 marks)

(1 mark for the correct arrangement of atoms;1 mark for the correct labelling of silicon andcarbon atoms) (2)

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Part B

e) Silicon combines with chlorine to form silicon tetrachloride (SiCl4). Draw an electron diagram of the chloride, showing electrons in the outermost shells only. (1 mark)

f) Explain why silicon carbide has a higher melting point than silicon tetrachloride in terms of their structures. (3 marks)

Silicon carbide has a giant covalent structure while silicon tetrachloride has a simple molecular structure. (1)

To melt silicon carbide, a lot of heat is needed to overcome the strong covalent bonds between the atoms. (1)

Weak van der Waals’ forces exist between molecules of silicon tetrachloride. Little heat is needed to separate the

molecules. (1)

85 Boron occurs naturally in two isotopes. The relative abundance of each isotope is shown in the table below:

Isotope 10B 11B

Relative abundance (%) 19.7 80.3

a) Compare these two isotopes in terms of the subatomic particles they contain. (2 marks)

• Both have 5 protons and 5 electrons. (1)

• 10B has 5 neutrons while 11B has 6 neutrons. (1)

OR

• Both have the same number of protons and electrons. (1)

• 10B and 11B have different number of neutrons. (1)

b) What is the meaning of the term ‘relative atomic mass’? (2 marks)

The weighted average relative isotopic mass of all the naturally occurring isotopes of that element (1)

on the 12C = 12.00 scale. (1)

(1)

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Part B

c) Calculate the relative atomic mass of boron. (2 marks)10 x 19.7 + 11 x 80.3

100 (1)

= 10.8 (1)

d) 10BCl3 and 11BCl3 are compounds formed respectively from the two isotopes of boron with chlorine. 10BCl3 reacts with water to give steamy fumes. State, with explanation, the expected observation when 11BCl3 reacts with water. (1 mark)

11BF3 would give steamy fumes because the chemical propertries of isotopes are the same. (1)

e) Boron is a metalloid. Suggest ONE physical property of boron. (1 mark)

Boron is a semi-conductor. (1)

f) The equation below shows the reaction between boron trifluoride and a fluoride ion.

BF3 + F– BF4–

i) In terms of the electrons involved, explain how the bond between the BF3 molecule and the F– ion is formed. (1 mark)

The bond pair electrons are provided by the F– ion. (1)

ii) Name the type of bond formed. (1 mark)


86 A part of the periodic table is shown below:

a) What determines the position of an element in the periodic table? (1 mark)

Its atomic number (1)

b) Across a period, the elements show a gradual change in some of their physical properties. State ONE such property. (1 mark)

Atomic size / metallic character of elements (1)

c) Name TWO elements which are mainly obtained from the sea. (1 mark)

Sodium and chlorine (0.5, 0.5)

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Part B

d) For each of the following pairs of elements, suggest ONE reaction in which they behave similarly.

i) Sodium and potassium (2 marks)

Sodium and potassium react with cold water vigorously. (1)

Hydrogen is evolved. / An alkaline solution is formed. (1)

ii) Chlorine and fluorine (1 mark)

Chlorine and fluorine react with metal to form salts. (1)

e) Which metal and non-metal in the above table would react most vigorously with each other? (1 mark)

Potassium and fluorine (0.5, 0.5)

f) Which element in the third period has the highest melting point? Explain in terms of the structure of the element. (3 marks)

Silicon has the highest melting point. (1)

Silicon has a giant covalent structure. (1)

To melt silicon, a lot of heat is needed to overcome the strong covalent bonds between the atoms. (1)

g) The atomic number of krypton (Kr) is 36. The electronic arrangement of a krypton atom is 2,8,x,y. What are the values of x and y? (1 mark)

x = 18 (0.5)

y = 8 (0.5)

h) Rubidium (Rb) is a Group I element. Its relative atomic mass is larger than that of potassium.

i) Suggest whether rubidium or potassium is more reactive. (1 mark)

Rubidium is more reactive. (1)

ii) Suggest a method to store rubidium in the laboratory. (1 mark)

It should be stored in paraffin oil. (1)

87 With reference to the part of the periodic table shown, answer the following questions.

67

Part B

a) Name ONE metalloid in the above table. (1 mark)

Boron / silicon (1)

b) Name TWO elements which make up 99% of air. (1 mark)

Nitrogen and oxygen (0.5, 0.5)

c) Explain why argon is monoatomic. (2 marks)

An argon atom has 8 electrons in its outermost shell. A special stability is obtained when this happens. (1)

An argon has very little tendency to share electrons with other argon atoms. Therefore argon is monoatomic. (1)

d) Name the group to which lithium and sodium belong. (1 mark)

Alkali metals (1)

e) In what way are the electronic arrangements of atoms of lithium and sodium

i) similar to each other? (1 mark)

They have the same number of outermost shell electrons. (1)

ii) different from each other? (1 mark)

They have different number of occupied electron shells. 1)

f) Point out the gradual change in the reactivity of Group II elements down the group. (1 mark)

The reactivity of Group II elements increases down the group. (1)

g) Suggest TWO gradual changes in the physical properties of Group VII elements down the group. (2 marks)

There is a gradual increase in the melting / boiling point of the elements. (1)

There is a gradual change in the intensity of the colour of the elements. (1)

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Part B

h) Describe the structure and bonding in aluminium with the help of a diagram. (3 marks)

Aluminium has a giant metallic structure. It consists of tightly packed positive ions surrounded by a sea of delocalized

electrons. (1)

The attractive forces between the electrons and positive ions hold the particles of aluminium together. (1)

88 A portion of the periodic table is shown below.

a) How are the elements arranged in the periodic table? (1 mark)

Increasing atomic number (1)

b) What is the similarity in the electronic arrangement of atoms of elements in the same period? (1 mark)

They have the same number of occupied electron shells. (1)

c) Which element in Group I has the smallest atomic size? (1 mark)

Lithium / Li (1)

d) Suggest why Group 0 elements seldom form compounds. (1 mark)

Atoms of Group 0 elements have stable electronic structure. (1)

e) i) Which is the most reactive metal in the above table? (1 mark)

Potassium / K (1)

(1)

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Part B

ii) Suggest how the most reactive metal should be stored. (1 mark)

It should be stored in paraffin oil. (1)

iii) State ONE hazard warning label that should be displayed on a reagent bottle containing that metal. (1 mark)

Flammable / corrosive (1)

f) Which of the above elements is used to make computer chips? (1 mark)

Silicon / Si (1)

g) Suggest ONE use of chlorine. (1 mark)

Making bleach / hydrochloric acid / organic solvents (1)

h) Balloons filled with different noble gases were tied to a bar. They were held horizontally at the same height and then released. The positions of two of the balloons 5 seconds after release are shown in the diagram.

Predict the position of the balloon filled with krypton (Kr) after 5 seconds. (1 mark)

Lower than argon (1)

89 The following questions refer to the incomplete periodic table shown below.

a) Which of the above elements are metals. (1 mark) f, h (0.5, 0.5)

b) List FOUR typical properties of metals. (4 marks)

Any four of the following:

• Melting / boiling point usually high (1) • Shiny appearance (1) • Good conductor of electricity (1)

• Good conductor of heat (1) • Ductile / malleable (1)

• Lose electrons / form positive ions (1)

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Part B

c) How many occupied electron shells are there in an atom of f? (1 mark) 3 (1)

d) Which element forms an ion carrying 1 negative charge? (1 mark) d (1)

e) Which element has an octet of electrons in the outermost shell of its atom? (1 mark) e (1)

f) i) Name the group to which h belongs. (1 mark) Alkali metals (1)

ii) Suggest TWO safety precautions for handling h in the laboratory. (2 marks)

Any two of the following:

• Wear safety glasses. (1) • Use forceps. (1) • Use a safety screen. (1)

g) Name the group to which e belongs. (1 mark)

Noble gases (1)

h) Which metal and non-metal in the above table would react most vigorously with each other? (1 mark)

d and h (0.5, 0.5)

i) b and f can combine to form a compound X. Draw an electron diagram of X, showing electrons in the outermost shells only. (1 mark)

90 The circuit shown below is set up and the solid lead(II) bromide is heated until it becomes motlen.

(1)

71

Part B

When the lead(II) bromide becomes molten, the bulb lights up.

a) Suggest a suitable material for making electrodes X and Y. (1 mark)

Nichrome / graphite (1)

b) What would be observed at electrode X? (1 mark)

A reddish brown gas evolves. (1)

c) What would be observed at electrode Y? (1 mark)

A white shiny solid deposits on the electrode. (1)

d) Suggest a place in the laboratory where this experiment could be carried out safely. Briefly explain your answer. (2 marks)

Inside a fume cupboard (1)

The reddish brown gas (bromine) evolved is toxic. (1)

e) State what will happen to the bulb when heating is stopped and the molten lead(II) bromide is allowed to cool down gradually to room temperature. Explain your answer. (3 marks)

The light bulb gradually goes out. (1)

As the temperature drops, movement of ions in molten lead(II) bromide slows down. Therefore a smaller current flows

through the external circuit. (1)

When the molten lead(II) bromide becomes solid, there are no mobile ions. Hence no current flows through the external

circuit. (1)

91 A tiny potassium permanganate crystal was placed at the centre of a piece of filter paper moistened with sodium sulphate solution. A d.c. power supply was then applied. Within a few minutes, a coloured patch was seen to develop on the filter paper.

a) What was the purpose of moistening the filter paper with sodium sulphate solution? (1 mark)

For the conduction of electricity (1)

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Part B

b) i) What was the colour of the patch developed on the filter paper? (1 mark)

Purple (1)

ii) Sketch the position where the coloured patch would be expected to develop. (Positive and negative electrodes must be shown.) (2 marks)

c) The positive and negative electrodes were then reversed after some time. Briefly explain what would be observed. (2 marks)

The coloured patch would move towards the new position of the positive electrode (1)

because the negative permanganate ions would be attracted towards the positive electrode. (1)

92 The diagram shows an experimental set-up for studying the reaction of lithium with water.

a) Describe what you would observe when the lithium reacts with the water in this experiment. (3 marks)

Any three of the following:

• Lithium fizzes / produces a gas. (1)

• The universal indicator turns blue / purple (alkaline colour). (1) • The water level in the test tube goes down (or gas

fills the test tube). (1) • Lithium moves around on the surface of water. (1) • Lithium dissolves. (1)

(2)

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Part B

b) Write a word equation for the reaction of lithium with water. (1 mark)

lithium + water lithium hydroxide + hydrogen (1)

c) Caesium is another Group I element. Suggest whether caesium or lithium is more reactive. (1 mark)

Caesium is more reactive. (1)

d) The graph shows the melting points of the Group I metals plotted against the atomic numbers.

i) Describe fully how the melting point changes as the atomic number increases. (2 marks)

The melting point decreases as the atomic number increases (1)

and the rate of decrease slows down. (1)

ii) Francium has an atomic number 87.

Use the graph to estimate the melting point of francium. (1 mark)

26 °C (1)

e) Elements in Group I can react with elements in Group VII.

Look at the four examples below.

A potassium + iodine potassium iodide B lithium + chlorine lithium chloride C potassium + chlorine potassium chloride D lithium + iodine lithium iodide

i) Which of the above reactions is the most vigorous? (1 mark)

C (1)

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Part B

ii) Explain your answer in (i) by describing the reactivity trends in the periodic table. (2 marks)

The reactivity of Group I elements increases as we move down the group (i.e. potassium is more reactive than

lithium). (1)

The reactivity of Group VII elements decreases as we move down the group (i.e. chlorine is more reactive than

iodine). (1)

93 The following table lists the atomic numbers of some elements in Group II.


Be 4

Mg 12

Ca 20

Sr 38

a) In what way are the electronic arrangements of atoms of magnesium and calcium

i) similar to each other? (1 mark)

They have the same number of outermost shell electrons. (1)

ii) different from each other? (1 mark)

They have different number of occupied electron shells. (1)

b) A student added a few pieces of calcium granules into a beaker of cold water. Calcium gave a colourless gas with cold water.

i) State ONE more observation when calcium reacted with water. (1 mark)

Calcium sinks in water. / Calcium dissolves. (1)

ii) The student recorded the following observation in her laboratory report:

‘Evolution of the colourless gas was at first slow but became faster after some time.’

Suggest an explanation for the student’s observation. (2 marks)

Calcium is covered by a layer of calcium oxide. (1)

Reaction between calcium and water starts only when the oxide layer dissolves. (1)

c) The electronic arrangement of a strontium (Sr) atom is 2,8,x,8,y. What are the values of x and y? (1 mark)

x = 18 (0.5)

y = 2 (0.5)

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Part B

d) Suggest whether strontium or calcium is more reactive. (1 mark)

Strontium is more reactive than calcium. (1)

e) Strontium-90 (90Sr) is a radioactive isotope of strontium, and is one of the dangerous by-products of nuclear fission.

i) Explain the meaning of the term ‘isotope’. (2 marks)

Isotopes are different atoms of an element which have the same number of protons (1)

but a different number of neutrons. (1)

ii) Children’s teeth require a large amount of calcium to grow. Scientists found that in areas where nuclear weapon tests were conducted above the ground, children’s teeth contained a higher level of 90Sr.

Suggest a reason for the findings of the scientists. (2 marks)

The chemical properties of strontium are similar to those of calcium. (1)

Thus strontium can replace some of the calcium required. (1)

94 The following table shows the melting and boiling points of chlorides of some Period 3 elements of the periodic table.

Sodium chloride

Magnesium chloride

Phosphorus trichloride

Sulphur dichloride

Melting point (°C) 808 712 –91 –80

Boiling point (°C) 1 463 1 418 74 59

a) Draw an electron diagram of magnesium chloride, showing electrons in the outermost shells only. (1 mark)

(1)

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Part B

b) i) Draw an electron diagram of sulphur dichloride, showing electrons in the outermost shells only. (1 mark)

ii) Suggest the physical state of sulphur dichloride at room temperature and pressure. (1 mark)

Liquid (1)

c) Explain the difference in the melting points of the above four chlorides in terms of their structures. (4 marks)

Sodium chloride and magnesium chloride have giant ionic structures. (1)

To melt them, a lot of heat is needed to overcome the strong ionic bonds between the ions. Hence sodium chloride

and magnesium chloride have high melting points. (1)

Phosphorus trichloride and sulphur dichloride have simple molecular structures. (1)

The attractive forces between the molecules are weak. Little heat is needed to separate the molecules. Hence

phosphorus trichloride and sulphur dichloride have low melting points. (1)

d) Discuss, with explanation, the electrical conductivity of magnesium chloride with reference to the type and property of the particles in it. (3 marks)

Magnesium chloride conducts electricity in molten state or aqueous solution but not in solid state. (1)

In solid state, the ions in magnesium chloride are held together by strong ionic bonds. They are not free to move. (1)

The ions become mobile in molten state or aqueous solution. (1)

e) Predict whether sodium chloride is soluble in water. Explain your answer. (3 marks)

Sodium chloride is soluble in water. (1)

Strong attractive forces exist between ions in sodium chloride and water molecules. (1)

These forces cause the ions to move away from the solid and go into the water. (1)

(1)

77

Part B

95 X, Y and Z are three elements in the periodic table, with the sum of their atomic numbers equal to 46. Moreover, both X and Y are Group VII elements, while the atomic number of X is smaller than that of Y.

a) What are elements X, Y and Z? (3 marks)

X fluorine (1)

Y chlorine (1)

Z calcium (1)

b) Name the group to which Z belongs. (1 mark)

Alkaline earth metals (1)

c) Draw an electron diagram of the compound P formed from X and Y, showing electrons in the outermost shells only. (1 mark)

d) Draw an electron diagram of the compound Q formed from X and Z, showing electrons in the outermost shells only. (1 mark)

e) Compare the melting points of P and Q. Explain your answer. (3 marks)

The melting point of Q is higher than that of P. (1)

To melt Q, a lot of heat is needed to overcome the strong ionic bonds between the ions. (1)

The attractive forces between the molecules of P are weak. Little heat is needed to separate the molecules. (1)

(1)

(1)

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Part B

F) X combines with nitrogen to form a nitride. Draw an electron diagram of the nitride, showing electrons in the outermost shells only. (1 mark)

(1)

g) Z combines with nitrogen to form a nitride. Draw an electron diagram of the nitride, showing electrons in the outermost shells only. (1 mark)

(1)

96 The following table shows some information about some species. They can be atoms or ions.

SpeciesAtomicnumber

Massnumber

Number of

protons electrons neutrons

A 8 16 8 8 8

B 8 18 8 8 10

C 8 16 8 10 8

D 9 19 9 9 10

E 12 24 12 10 12

F 12 24 12 12 12 (0.5 x 12)

a) Complete the above table. (6 marks)

b) What is the relationship between A and B? (1 mark)

They are isotopes. (1)

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Part B

c) What is the relationship between A and C? (1 mark)

C is an anion of A. (1)

d) What is the relationship between E and F? (1 mark)

E is a cation of F. (1)

e) D exists as diatomic molecules.

Draw an electron diagram of a molecule of D, showing electrons in the outermost shells only. (1 mark)

(1)

f) X is a compound formed from A and D, while Y is a compound formed from A and F.

i) Draw an electron diagram of X, showing electrons in the outermost shells only. (1 mark)

(1)

ii) Draw an electron diagram of Y, showing electrons in the outermost shells only. (1 mark)

(1)

iii) Compare the melting points of X and Y. Explain your answer. (3 marks)

The melting point of Y is higher than that of X. (1)

To melt Y, a lot of heat is needed to overcome the strong ionic bonds between the ions. (1)

The attractive forces between the molecules of X are weak. Little heat is needed to separate the molecules. (1)

80

Part B

97 The electron diagram of ammonium chloride is shown below:


a) Identify the type of bond which exists between the two ions. (1 mark)

Ionic bond (1)

b) Identify the type of bond which exists between nitrogen and hydrogen. (1 mark)

Covalent bond (1)

c) When a hydrogen ion reacts with an ammonia molecule, an ammonium ion is formed.

i) Give the name of the type of bond formed when a hydrogen ion reacts with an ammonia molecule. (1 mark)


ii) Describe how this bond is formed in the ammonium ion. (1 mark)

The nitrogen atom supplies both bonding electrons to the hydrogen ion. (1)

d) Explain whether ammonium chloride is soluble in water. (3 marks)

Ammonium chloride is soluble in water. (1)

Strong attractive forces exist between ions in ammonium chloride and water molecules. (1)

These forces cause the ions to move away from the solid and go into the water. (1)

e) Describe a chemical test to show the presence of chloride ions in a solid sample. State the expected observation(s). (3 marks)

Dissolve the sample in water. (1)

Then add excess dilute nitric acid, followed by silver nitrate solution. (1)

A white precipitate forms. (1)

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Part B

98 Explain the following:

a) Argon seldom forms compounds with other elements. (2 marks)

An atom of argon has 8 electrons in its outermost shell. (1)

A special stability is obtained when this happens. Hence argon seldom forms compounds with other elements. (1)

b) Magnesium and calcium show similar chemical properties. (1 mark)

Atoms of magnesium and calcium have the same number of outermost shell electrons. (1)

c) A sulphur atom tends to form an ion carrying two negative charges. (1 mark)

A sulphur atom has an electronic arrangement 2,8,6. It obtains a stable electronic arrangement (2,8,8) by gaining

two electrons. (1)

d) Copper has a high melting point. (2 marks)

The ions in copper are packed closely and the metallic bonds holding them together are very strong. (1)

To melt a piece of copper, a lot of heat is needed to overcome the strong attractive forces. Hence copper has a high

melting point. (1)

e) Quartz is a solid which melts at a high temperature while carbon dioxide is a gas at room temperature. (4 marks)

Quartz has a giant covalent structure. (1)

To melt quartz, a lot of heat is needed to overcome the strong covalent bonds between the atoms. Hence quartz has a

high melting point. (1)

Carbon dioxide has a simple molecular structure. (1)

The attractive forces between the molecules are weak. Little heat is needed to separate the molecules. Hence carbon

dioxide has a low boiling point. (1)

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Part B

99 Consider the substances listed below:

argon carbon dioxide hydrogen chloride iodine silicon dioxide sodium chloride

The following diagram shows the arrangements of particles in three substances X, Y and Z.

a) For each case, choose ONE substance from the above list which has arrangement of particles as shown under room temperature and pressure. (3 marks)

Substance X sodium chloride (1)

Substance Y argon (1)

Substance Z iodine (1)

b) Name the attractive forces that exist between particles in substance Y. (1 mark)

Van der Waals’ forces (1)

c) Predict and explain the following properties of substance X:

i) hardness; (2 marks)

X is hard (1)

due to the strong ionic bonds between the ions. Relative motion of the ions is restricted. (1)

ii) electrical conductivity in solid and molten states. (3 marks)

X does not conduct electricity in solid state but it does in molten state. (1)

In solid state, the ions in X are held together by strong ionic bonds. They are not free to move. (1)

The ions become mobile in molten state. (1)

d) Predict and explain the following properties of substance Z:

i) solubility in water; (2 marks)

Z is slightly soluble in water. (1)

The weak attractive forces between molecules of Z and water are not strong enough to overcome the attractive

forces between water molecules. (1)

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Part B

ii) solubility in non-aqueous solvents; (2 marks)

Z is very soluble in non-aqueous solvents. (1)

The attractive forces between molecules of non-aqueous solvents are similar to those between molecules of Z. Hence

molecules of Z and non-aqueous solvents mix together easily. (1)

iii) electrical conductivity. (2 marks)

Z does not conduct electricity (1)

becsuse it does not contain mobile electrons or ions. (1)

100 A new element X has been recently discovered. It is a solid with a low melting point. It reacts violently with water and catches fire in the reaction. An alkaline solution is formed.

a) In which group of the periodic table should X be placed? (1 mark)

Group I (1)

b) Suggest how X can be stored safely in the laboratory. (1 mark)

Store X in paraffin oil. (1)

c) X forms a compound with bromine.

i) Determine the chemical formula of the compound. (1 mark)

XBr (1)

ii) Do you expect this compound to be volatile? Explain. (3 marks)

The compound is not volatile. (1)

Its ions are held together by strong ionic bonds. (1)

A lot of heat is needed to overcome the strong ionic bonds. (1)

iii) Discuss, with explanation, the electrical conductivity of the compound with reference to the type and property of the particles in it. (3 marks)

The compound conducts electricity in molten state or aqueous solution but not in solid state. (1)

In solid state, the ions in the compound are held together by strong ionic bonds. They are not free to move. (1)

The ions become mobile in molten state or aqueous solution. (1)

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Part B

101 The diagrams below show the structures of diamond and graphite. Diamond and graphite are allotropes.

.

a) Explain the meaning of the term ‘allotrope’. (2 marks)

Allotropes are two (or more) forms of the same element (1)

in which the atoms or molecules are arranged in different ways. (1)

b) Do you expect diamond to dissolve in water? Explain your answer. (2 marks)

Diamond is insoluble in water. (1)

This is because the atoms are held together by strong covalent bonds. It is very difficult to separate the atoms. (1)

c) Based on the structure of diamond, suggest ONE use of it. (1 mark)

As a stone cutter (1)

d) Explain why diamond is harder than graphite. (2 marks)

In graphite, the layers of carbon atoms are held by weak van der Waals’ forces. The layers can easily slide over each

other. Hence graphite is quite soft. (1)

In diamond, each carbon atom is bonded to other carbon atoms by strong covalent bonds. Relative motion of the

atoms is restricted. Hence diamond is very hard. (1)

e) Explain why graphite is used as lubricant. (2 marks)

Graphite has a layered structure. Weak van der Waals’ forces exist between the layers. (1)

The layers can easily slide over each other. (1)

Hence graphite has a slippery feel.

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Part B

f) State a property NOT mentioned above which graphite shares with metals. Explain the cause of this property. (3 marks)

Graphite is a good conductor of electricity. (1)

Graphite has a layered structure. Within each layer, each carbon atom uses three outermost shell electrons in

forming covalent bonds with three other atoms. (1)

The remaining electron is delocalized between the layers of carbon atoms. (1)

Graphite is a good conductor of electricity due to the presence of delocalized electrons.

102 Diamond and graphite are different forms of the same element. The structure of diamond is shown below.

a) What type of structure does diamond have? (1 mark)

Giant covalent structure (1)

b) Explain why carbon dioxide is a gas at room temperature and diamond is a solid which melts at a high temperature. (2 marks)

The attractive forces between carbon dioxide molecules are weak. Little heat is needed to separate the molecules. Hence

carbon dioxide has a low boiling point. (1)

Diamond consists of a network of covalent bonds. A lot of heat is needed to overcome the strong covalent bonds

between the atoms. Hence diamond has a high melting point. (1)

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Part B

c) Graphite is mixed with clay to make pencil leads.

i) Sketch a labelled diagram to show the arrangement of atoms in graphite. (2 marks)

ii) Suggest why this crystal structure of graphite enables it to leave a mark when a pencil is drawn across a sheet of paper. (2 marks)

When graphite is pressed onto a peice of paper, the layers of atoms slide over each other (1)

and flake off easily onto the paper. (1)

103 Silicon (Si) and germanium (Ge) have the same crystal structure, as shown below:

a) What type of structure do silicon and germanium have? (1 mark)

Giant covalent structure (1)

b) Silicon occurs in nature as silicon dioxide in sand and quartz.

Draw the three-dimensional structure of silicon dioxide. (2 marks)

(1 mark for the hexagonal arrangement of atoms;1 mark for labelling the van der Waals’ forces between the layers of atoms) (2)

(1 mark for the correct arrangement of atoms;1 mark for the correct labelling of silicon and oxygen atoms) (2)

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Part B

c) Silicon combines with chlorine to form silicon tetrachloride (SiCl4). Draw an electron diagram of the chloride, showing electrons in the outermost shells only. (1 mark)

d) Explain why silicon dioxide has a higher melting point than silicon tetrachloride in terms of their structures. (2 marks)

To melt silicon dioxide, a lot of heat is needed to overcome the strong covalent bonds between the atoms. (1)

The attractive forces between silicon tetrachloride molecules are weak. Little heat is needed to separate the molecules. (1)

e) The table below gives the relative abundance of each isotope in a sample of germanium, Ge.

Isotope 70Ge 72Ge 74Ge

Relative abundance (%) 24.4 32.4 43.2

What is the relative atomic mass of Ge? (2 marks)70 x 24.4 + 72 x 32.4 + 74 x 43.2

100 (1)

= 72.4 (1)

(1)

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Part B

104 At room temperature, both sodium metal and sodium chloride are crystalline solids.

a) The diagram below shows part of the lattice of sodium chloride.

i) In this diagram, mark all sodium ions with a positive (+) sign and all chloride ions with a negative (–) sign. (1 mark)

(1)

ii) What is the number of neighbouring chloride ions directly attached to each sodium ion in crystalline sodium chloride? (1 mark)

6 (1)

b) i) Explain how the particles are held together in solid sodium metal. (1 mark)

The particles in solid sodium metal are held together by a ‘sea’ of mobile electrons. (1)

ii) Explain how the particles are held together in solid sodium chloride. (1 mark)

The particles in solid sodium chloride are held together by ionic bonds. (1)

iii) The melting point of sodium chloride is much higher than that of sodium metal. What can be deduced from this information? (1 mark)

The ionic bonding in sodium chloride is stronger / requires more heat to break than the metallic bonding in

sodium. (1)

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Part B

c) Compare the electrical conductivity of solid sodium metal with that of solid sodium chloride. Explain your answer. (3 marks)

Solid sodium conducts electricity but solid sodium chloride does not. (1)

Solid sodium contains mobile electrons (1)

but the ions in solid sodium chloride are not free to move. (1)

d) Using sodium as an example, describe the bonding in metals. Hence explain why metals are malleable. (2 marks)

Ions in sodium are packed in layers. (1)

As the metal is struck by a hammer, the ion layers slide through the ‘sea’ of electrons to new positions. The metal does

not break because the ions are still bound together by the ‘sea’ of electrons. (1)

As a result, sodium is malleable.

105 The symbols p, q, r, s, t, u, v and w represent eight consecutive elements in the second and third periods of the periodic table. The table below lists their boiling points:

Element p q r s t u v w

Boiling point (°C) 2 480 3 930 4 830 –196 –183 –190 –246 890

Answer: Be B C N O F Ne Na

a) Deduce from the above information which elements r and s represent respectively. (3 marks)

Element r has the highest boiling point and (1)

a sudden drop in boiling point occurs from r to s. (1)

Hence r is carbon while s is nitrogen. (1)

b) Explain why element t has a low boiling point. (2 marks)

The attractive forces between the molecules of t are weak. (1)

Little heat is needed to separate the molecules. (1)

c) Indentify ONE metalloid in the above table. (1 mark)

q (1)

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Part B

d) State, with explanation, which of the elements is stored in paraffin oil. (2 marks)

Element w is stored in paraffin oil (1)

as it is very reactive. (1)

e) Suggest ONE use of element v. (1 mark)

In advertising signs (1)

f) X is a compound formed from elements t and u. Draw an electron diagram of X, showing electrons in the outermost shells only. (1 mark)

g) Y is a compound formed from elements t and w. Draw an electron diagram of Y, showing electrons in the outermost shells only. (1 mark)

h) Compare the melting points of X and Y. Explain your answer. (3 marks)

The melting point of Y is higher than that of X. (1)

To melt Y, a lot of heat is needed to overcome the strong ionic bonds between the ions. (1)

The attractive forces between the molecules of X are weak. Little heat is needed to separate the molecules. (1)

(1)

(1)

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Part B

106 The diagram below shows the relative electrical conductivities of the first three elements in Period 3.

a) Describe the bonding in magnesium. Hence explain why magnesium is a good conductor of electricity. (3 marks)

The outermost shell electrons of each magnesium atom are free to move randomly in magnesium. (1)

Thus, magnesium consists of positively charged ions surrounded by a ‘sea’ of electrons. (1)

Magnesium is a good conductor of electricity due to the movement of mobile electrons in the metal. (1)

b) Explain why the electrical conductivity of aluminium is higher than that of magnesium. (2 marks)

Each aluminium atom has three outermost shell electrons while a magnesium atom has two. (1)

There are more delocalized electrons in aluminium. (1)

So, the electrical conductivity of aluminium is higher.

c) Explain why metals are ductile. (2 marks)

Ions in a metal are packed in layers. (1)

As the metal is struck by a hammer, the ion layers slide through the ‘sea’ of electrons to new positions. The metal does

not break because the ions are still bound together by the ‘sea’ of electrons. (1)

As a result, the metal is ductile.

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Part B

d) Explain whether molten sulphur can conduct electricity. (2 marks)

Molten sulphur cannot conduct electricity (1)

because it does not contain mobile electrons or ions. (1)

107 Read the passage below and answer the questions that follow.

Development of the periodic table

In 1869, Mendeléev arranged the elements in the form of the periodic table. Before this many other scientists tried to make sense of all the information about the elements.

The table below is part of the table of elements devised by the English chemist John Newlands in 1864. He arranged the elements in order of their relative atomic masses. He found a repeating pattern, with elements having similar properties in the vertical columns (Groups).

Many scientists were critical of the pattern suggested by Newlands.

The diagram below shows a version of Mendeléev’s Periodic Table. Mendeléev placed most of the elements in order of relative atomic mass. This table became accepted by other scientists.

H Li Be B C N O

F Na Mg Al Si P S

Cl K Ca Cr Ti Mn Fe

Co / Ni Cu Zn Y In As Se

Br Rb Sr Ce / La Zr Di / Mo Ro / Ru

Group1

Group2

Group3

Group4

Group5

Group6

Group7

Group8

Period 1 H

Period 2 Li Be B C N O F

Period 3 Na Zn Al Si P S Cl

Period 4K

CuCa

Zn?

?Ti

?V

AsCr

SeMn

BrFe Co Ni

Period 5Rb

AgSr

CdY

InZr

SnNb

SbMo

Te?

IRu Rh Pd

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Part B

a) i) Which group of elements, present in the modern periodic table, is missing from Newlands’ table above? (1 mark)

Group 0 (1)

ii) Explain why this group was missing from Newlands’ classification of elements. (1 mark)

Not yet discovered at that time (1)

b) Newlands put hydrogen, fluorine and chlorine in the same group. Give ONE property of hydrogen which makes it similar to fluorine and chlorine. (1 mark)

Exists as diatomic molecules / exists as a gas at room conditions / any other general property of non-metals (1)

c) Suggest why other scientists were critical of Newlands’ table.

You should give examples from the table and use your knowledge of the chemistry of the elements. (4 marks)


• Many elements in the groups have very dissimilar properties, e.g. K and Cu. (2)

• Two elements were put in one place, e.g. Ce and La. (2)

• Metals and non-metals were mixed up, e.g. Cl and Co in the same group. (2)

d) Give TWO ways in which Mendeléev’s table improved on Newlands’ table. (2 marks)


• Elements with similar properties were grouped together. (1)

• Gaps left for elements to be added when discovered. (1)

• A new group created / iron, cobalt and nickel put in a group. (1)

• Metals and non-metals were separated. (1)

e) Suggest how elements are arranged in a modern periodic table. (1 mark)

In order of increasing atomic number (1)

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Part B


A new form of carbon

The carbon allotropes, diamond and graphite, have been known for centuries. In 1985, a new form of carbon – buckminsterfullerene – was discovered. This new form of carbon contains C60 molecules. Each C60 molecule is formed by 60 carbon atoms bonded together like a football as shown in the diagram below:

The new form of carbon is virtually insoluble in water, but soluble in non-aqueous solvents, such as toluene.

Interest in buckminsterfullerene has led to the discovery of a related group of carbon structures referred to as nanotubes. Nanotubes may be viewed as rolled up segments of graphite.

Carbon nanotubes have a high strength. Carbon nanotube-based materials are being widely researched to develop ultra lightweight and extremely strong materials.

a) What is meant by the term ‘allotropes’? (2 marks)

Allotropes are two (or more) forms of the same element (1)

in which the atoms or molecules are arranged in different ways. (1)

b) What type of structure does buckminsterfullerene have? Expain your answer. (3 marks)

Buckminsterfullerene has a simple molecular structure. (1)

Buckminsterfullerene is soluble in non-aqueous solvents. (1)

It can be deduced that the attractive forces between molecules of buckminsterfullerene are similar to those

between molecules of non-aqueous solvents. (1)

Hence it can be concluded that buckminsterfullerene has a simple molecular structure.

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Part B

c) How would you expect the melting point of buckminsterfullerene to compare with that of diamond? Explain your answer. (3 marks)

The melting point of diamond is higher than that of buckminsterfullerene. (1)

Diamond has a giant covalent structure. The carbon atoms are held together by strong covalent bonds. (1)

There are weak van der Waals’ forces between the buckminsterfullerene molecules. (1)

More heat is needed to break the strong covalent bonds between atoms in diamond. Hence diamond has a higher

melting point.

d) Explain the high strength of carbon nanotubes with reference to the bonding in them. (1 mark)

The carbon atoms are held together by strong covalent bonds. (1)

e) Graphite is used to make electrodes in dry cells. It is also used to make strong but lightweight fishing rods.

i) Explain why graphite can conduct electricity with reference to its structure. (3 marks)

In graphite, the carbon atoms are arranged in flat parallel layers. (1)

Within each layer, each carbon atom uses three electrons in forming covalent bonds with three other carbon

atoms. (1)

The remaining outermost shell electron of each carbon atom is delocalized between the layers of carbon atoms. (1)

ii) Explain why graphite can bend so that it is suitable for making a fishing rod. (2 marks)

Graphite has a layered structure. Weak van der Waals’ forces exist between the layers. (1)

The layers of atoms can slide over each other easily. (1)

f) Suggest and explain how you would distinguish between buckminsterfullerene and graphite by a physcial method. (3 marks)

Adding a non-aqueous solvent to each solid separately, buckminsterfullerene is soluble while graphite is insoluble. (1)

Buckminsterfullerene has a simple molecular structure and is soluble in non-aqueous solvents. (1)

Graphite has a giant covalent structure. It is insoluble in most solvents. (1)

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Part B


Chemistry of fireworks

Aerial shells are the most common types of fireworks for public displays. A shell consists of a paper tube filled with stars and a black powder. Stars are small lumps consisting of an oxidizing agent, a reducing agent and metal salts. The black powder is a mixture of carbon powder, sulphur powder and potassium nitrate powder. Located just below the shell is a lift charge containing the black powder as well.

Upon ignition, the potassium nitrate, sulphur and carbon (in the black powder) in the lift charge react to form carbon dioxide and nitrogen gases, and potassium sulphide.

potassium nitrate + carbon + sulphur potassium sulphide + carbon dioxide + nitrogen

The shell is sent up into the air. At the precise altitude, the black powder inside the shell is ignited, causing the shell to explode. The explosion also ignites the stars, scattering them in all directions across the sky.

The colours of fireworks are produced by burning metal salts. For example, a red colour can be produced by using strontium nitrate while a green colour produced by using barium nitrate.

a) Explain the meaning of the term ‘mixture’. (2 marks)

A mixture consists of two or more pure substances (1)

which have not been chemically joined together. (1)

b) Draw an electron diagram of a nitrate ion, showing electrons in the outermost shells only. (1 mark)

c) Explain how the lift charge sends the shell into the air. (2 marks)

The pressure from the expanding gases propels the shell into the air (2)

d) i) What solid residue is left behind when the black powder explodes? (1 mark)

Potassium sulphide (1)

ii) Wht is the chemical formula of the solid suggested in (i)? (1 mark)

K2S (1)

(1)

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Part B

e) i) Name the group to which strontium (Sr) and barium (Ba) belong. (1 mark)

Alkaline earth metals (1)

ii) Write down the chemical formula of strontium nitrate. (1 mark)

Sr(NO3)2 (1)

f) A manufacturer wants to produce fireworks giving a yellow colour. Suggest a metal salt the manufacturer may add. (1 mark)

Sodium nitrate / any sodium compound (1)

110 Below is a sketch of the melting points of some Period 3 elements.

Discuss how the melting points of the elements are related to their bondings and structures. (9 marks)

(For this question, you are required to give answers in paragraph form.)

Sodium, magnesium and aluminium are metals. The strength of the metallic bond depends on the number of delocalized

electrons in the metal structure. (1)

Sodium has one outermost shell electron per atom, magnesium has two while aluminium has three. The strength of metallic

bond and hence the melting point increase from sodium to aluminium. (1)

Silicon has a giant covalent structure. Each silicon atom is covalently bonded to four other silicon atoms. (1)

To melt silicon, a lot of heat is needed to overcome the strong covalent bonds between the atoms. Hence it has a very high

melting point. (1)

Phosphorus, sulphur and chlorine exist as simple molecules. The molecules are attracted to one another by weak van der

Waals’ forces. (1)

Little heat is needed to separate the molecules. Hence they have low melting points. (1)

(3 marks for organization and presentation)

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Part B

111 ‘When atoms combine, they can obtain the electronic arrangements of atoms of noble gases.’

Discuss, with reference to suitable examples, how atoms of Group VI elements obtain the electronic arrangements of atoms of noble gases. (9 marks)


Atoms of Group VI elements have six outermost shell electrons. They can obtain the electronic arrangements of atoms of

noble gases by gaining or sharing electrons. (1)

Oxygen is a Group VI element. Take the combination of oxygen and sodium as an example. An oxygen atom has

an electronic arrangement 2,6. It tends to gain two electrons to obtain the electronic arrangement of a stable neon atom

(2,8). (1)

Sodium is a Group I element. A sodium atom has an electronic arrangement 2,8,1. It tends to lose one electron to

obtain the electronic arrangement of a stable neon atom (2,8). (1)

When sodium and oxygen react, two sodium atoms would combine with one oxygen atom. (1)

Take the combination of oxygen and carbon as another example. An oxygen atom has an electronic arrangement

2,6 while that of a carbon atom is 2,4.

Both atoms require electrons to obtain the electronic arrangement of a stable neon atom (2,8). They achieve that by

sharing outermost shell electrons. (1)

One carbon atom forms a double bond with each of the two oxygen atoms. (1)


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Part B

112 ‘Potassium chloride and silicon tetrachloride have different melting points and electrical conductivities.’

Explain such differences with reference to their bonding and structures. (9 marks)


The melting point of potassium chloride is higher than that of silicon tetrachloride. (1)

Potassium chloride has a giant ionic structure.

To melt potassium chloride, a lot of heat is needed to overcome the strong ionic bonds between the ions. Hence potassium

chloride has a high melting point. (1)

Silicon tetrachloride has a simple molecular structure.

The attractive forces between the molecules are weak. Little heat is needed to separate the molecules. Hence silicon

tetrachloride has a low melting point. (1)

Potassium chloride conducts electricity in molten state or aqueous solution while silicon tetrachloride does not conduct

electricity. (1)

In the solid state, the ions in potassium chloride are held together by strong ionic bonds and are not free to move.

The ions become mobile when potassium chloride is in molten state or aqueous solution. Hence potassium chloride can

conduct electricity under these conditions. (1)

Silicon tetrachloride does not conduct electricity because it does not contain mobile electrons or ions. (1)


1B- Atom Structure, Bonding

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