Technical Science Notes Students Version

7/23/2019 Technical Science Notes Students Version

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1.1.

OBJECTIVES .......................................................................................... 3

1.2. INTRODUCTION ..................................................................................... 3

Chemistry: Its Central Role ............................................................................ 3

1.3. CLASSIFICATION OF MATTER .............................................................. 4

The States of Matter ...................................................................................... 4

Substances and Mixtures............................................................................... 4

Elements and Compounds............................................................................. 5

1.4.

GASES, LIQUIDS AND SOLIDS. ............................................................ 6

1.5. ATOM, MOLECULE, COMPOUND, ISOTOPE AND ION. ....................... 9

Atoms and Molecules .................................................................................... 9

Isotopes ....................................................................................................... 11

Formation of Ions ......................................................................................... 12

1.6. ATOMIC MASS AND MOLECULAR MASS ........................................... 12

Relative Atomic Mass .................................................................................. 14

Relative Molecular Mass .............................................................................. 15

Mole concept ............................................................................................... 16

Molar Mass .................................................................................................. 17

Empirical and Molecular Formula ................................................................ 17

CChhaapptteerr22..........................................................................................................................................................................1199

1.7. Objectives .............................................................................................. 19

4.1. Introduction ............................................................................................ 19

4.2. Periodic Classification of Elements ........................................................ 20


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CHAPTER 1

FUNDAMENTALS OF CHEMISTRY AND ATOMIC CONCEPT

1.1. OBJECTIVES

Upon completion of this chapter, students should have:

1. To distinguish matter based on their classifications and compositions.

2. To understand the structure of matter.

3. To distinguish the difference between chemical and physical changes in

phase change.

4. To understand the chemical changes occur in matter.

5. To identify the three phase of matter: solid, liquid and gas.

6. To explain the mole concept, and convert between grams, moles, and

atoms and molecules.

1.2. INTRODUCTION

Chemistry: Its Central Role

Science is a unified whole. Common scientific laws apply everywhere and on all

levels of organization. The various areas of science interact and support one

another.

Accordingly, chemistry not only is useful in itself but is also fundamental to other

scientific disciplines.

Matter can be described as stuff that makes up all material things; it is anything

that occupies space and has mass. Matter has mass; you can weigh it. Wood,

sand, water, air and people have mass and are therefore matter.


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Mass is a measure of the quantity of matter that an onject contains. The greater

he mass of an object, the more difficult it is to change its velocity.

1.3. CLASSIFICATION OF MATTER

The States of Matter

There are three familiar states of matter: solid, liquid and gas (Figure 1.1). They

can be classified by bulk properties (a macro view) or by arrangement of the

particles that comprise them (a molecular or micro view).

A solid object ordinarily maintains its shape and volume regardless of its location.

A liquid occupies a definite volume but assumes the shape of the occupied

portion of its container.

A gas maintains neither shape nor volume. It expands to fill completely whatever

container it occupies. Gases flow and are easily compressed.

Bulk properties of solids, liquids and gases are explained using the kinetic-

molecular theory.

In solids, the particles are close together and in fixed positions. In liquids, the

particles are close together, but they are free to move about. In gases, the

particles are far apart and are in rapid random motion.

Substances and Mixtures

Matter can be either pure or mixed (Figure 1.2). Pure matter is considered to be

a substance.


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A substance has a definite, or fixed, composition that does not vary from one

sample to another.

The composition of a mixture of two or more substances is variable. The

substances retain their identities. They do not change chemically; they simply

mix.

Mixtures can be separated by physical means. Mixtures can be either

homogeneous or heterogeneous. All parts of a homogeneous mixture have the

same composition and the same appearance.

Elements and Compounds

A substance is either an element or a compound.

An element is one of the fundamental substances from which all material things

are constructed. Elements cannot be broke down into simpler substances by any

chemical process.

A compound is a substance made up of two or more elements chemically

combined. Compounds have a fixed composition. For example, water has fixed

proportions, by mass, of hydrogen (H) and oxygen (O).


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Figure 0-1: A Scheme for Classifying Matter

1.4. GASES, LIQUIDS AND SOLIDS.

Gases, liquids, and solids are all made up of atoms, molecules and/or ions, but

the behaviors of these particles differ in the three phases.

How is matter

classified?


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Figure 0-2: Three States of Matter. a) Most solids have molecules (oratoms) that vibrate around fixed positions. b) in liquids the molecules arestill close but are free to move about like people in crowded room. c)

Molecules of gases are widely spaced apart and more freely and randomly.

In liquids, the particles are still in close contact but are move randomly arranged

and are freer to move about (Figure 1.2b). This is why liquids are able to flow to

conform to the shape of their container.

In gases, molecules are separated by relatively great distances and are moving

quite rapidly in random direction (Figure 1.2 c). In this state, the atoms or

molecules have essentially no interactions with one another.

Most solids can be change to liquids; that is, they can be melted. The solids are

heated, and the heat energy is absorbed by the particles of the solid. The energy

causes the particles to vibrate more vigorously until, finally, the forces holding the

particles in their regular arrangement are overcome. The solid becomes a liquid.

The temperature at which this happens is the melting point of the solid. A high

melting point is one indication that the forces holding a solid together are very

strong.

a) b) c)


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A liquid can change to a gas vapor in a process called vaporization. Again, one

need only supply sufficient heat to achieve this change. Energy is absorbed by

the liquid particles, which more faster and faster as a result. Finally, this

increasingly violent motion overcomes the attractive forces holding the liquid

particles in contact and the particles fly away from one another. The liquid

becomes a gas. The temperature at which this happens is the boiling point of

the liquid.

Removing energy from the sample and slowing down the particles can reverse

the entire sequence of changes. Vapor changes to liquid in a process called

condensation; liquid can change to solid in a process called freezing. Figure

1.3 presents a diagram of the changes in sates that occur as energy is added or

removed from a sample. Some substances go directly

Figure 0-3: Diagrams of changes in states of matter on heating or cooling


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1.5. ATOM, MOLECULE, COMPOUND, ISOTOPE AND ION.

Atoms and Molecules

An atom is the smallest characteristic part of an element. Each is composed of

atoms of a particular kind. For example, the element copper is made up of

copper atoms, and gold is made up of gold atoms. All copper atoms are alike in a

fundamental way and are different from gold atoms.

Atoms are made up of 3 subatomic particles namely protons, electrons and

neutrons. Protons and neutrons are located at the center of an atom in a tiny

core called the nucleus. Electrons move around the nucleus in circular orbits at

high velocities. Figure 1.4 shows the position of the 3 fundamental particles of an

atom.

Figure 0-4: Structure of an Atom

The smallest characteristic part of most compounds is a molecule. A molecule is

a group of atoms bound together as a unit. Each molecule of a given compound

has the same atoms in the same proportions as all the other molecules of the


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compound. For example, all water molecules have two hydrogen (H) atoms and

one oxygen (O) atom, as indicated by the formula H2O.

The charge and the relative mass in atomic mass units of each of the three

subatomic particles are given in Table 1.1 below:

Table 0-1 Charges and relative masses of subatomic particles

Particle Symbol Relative Mass

(a.m.u)

Charge Location in Atom

Proton p+ 1 1+ Nucleus

Neutron n 1 0 Nuceus

Electron e- 0.00054 1- Outside nucleus

Nuclear charge is the total positive charge contributed by all the protons in the

nucleus of an atom. For example, a sodium atom has a nuclear charge of +11

because it has 11 protons in its nucleus.

Atomic number (Z), is the total number of protons in the nucleus of each atomof an element (Z = p). In a neutral atom, the number of protons is equal to the

number of electrons (p = e).

Mass number (A) is the sum of all the protons and neutrons present in the

nucleus of an atom.

Mass number (A) = number of protons (p) + number of neutrons (n)

= atomic number (Z) + number of neutrons (n)


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Isotopes

Isotopes are atoms of an element that have the same atomic number but

different mass number. Therefore, isotopes of an element contain the samenumber of protons but different number of neutrons.

The chemical properties of an element are determined primarily by the protons

and electrons in its atoms; neutrons do not take part in chemical reactions under

normal conditions. Therefore, isotopes have the same chemical properties such

as density and rate of diffusion.

Collectively, the two principle nuclear particles, protons and neutrons, are called

nucleons. Isotopes are represented by symbols with subscripts and

superscripts.

In this general symbol, Z is the nuclear charge (atomic number or number f

protons), and A is the mass number or the nucleon number because it is thenumber of nucleons. (Nucleon number is the term recommended by the IUPAC).

Example 1.5.1

How many electrons are there in the nucleus?

Solutions

Number of neutrons = mass number (A)atomic number (Z)

= 23592

= 143

There are 143 neutron in the nucleus.


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Exercise 1.5.1A

How many neutrons are there in the nucleus?

Exercise 1.5.1B

A potassium isotope has 21 neutrons in its nucleus. What is the mass number

and name of the isotope?

Formation of Ions

In any given atom, the number of protons is always equal to the number of

electrons and therefore the negative charges of electrons balance out thepositive charges of the protons. Thus, an atom is electrically neutral. Neutral

atoms can lose or gain electrons and become charged. The charged atoms are

known as ions. Atom does not lose or gain proton in any chemical reaction.

A positively charged ion is known as cation which is formed when a neutral atom

releases an electron.

A negatively charged ion is known as anion which is formed when a neutral atom

accepts an electron.

Example:

Charge on aluminium ion = (13)(10) = +3

Charge on sulphide ion = (16) (18) = -2

1.6. ATOMIC MASS AND MOLECULAR MASS

Atomic mass is the mass of a specific isotope, most often expressed in unified

atomic mass unit (amu or u), where 1 amu is equal to 1/12 of the actual mass of


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carbon-12 (C-12). The atomic mass is the total mass of protons, neutrons and

electrons in a single atom. Atomic mass is also known as a relative atomic mass.

Most elements have several naturally occurring isotopes with different percent

abundance. The atomic mass shown in the periodic table for an element is the

average weight of the masses of all isotopes. It is known as the average atomic

mass.

Example 1.6.1

Give the number of protons, neutrons and electrons in each following species:

a) Na2011 b) Na22

11 c)17O d) Carbon14

Solution

a) The atomic number is 11, so there are 11 protons. The mass number is

20, so the number of neutrons is 20 11 = 9. The number of electrons is

the same as the number of protons that is 11.

b) The atomic number is the same as that in (a), or 11. The mass number is

22, so the number of neutrons is 22 11 = 11. The number of electrons is

11. Note that the species in (a) and (b) are chemically similar isotopes of

sodium.

c) The atomic number of oxygen is 8, so there are 8 protons. The mass

number is 17, so there are 178 = 9 neutrons. There are 8 electrons.

d) Carbon -14 can also be represented as 14C. The atomic number of carbon

is 6, so there are 146 = 8 neutrons. The number of electrons is 6.


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Exercise 1.6.1A

How many protons, neutrons and electrons are in the following isotope of copper:

63Cu?

Exercise 1.6.1B

How many protons, neutrons, and electrons are in

(a) An atom of 197Au

(b) An atom of strontium-90?

Answer:

a) 79 protons, 79 electrons, and 118 neutronsb) 38 protons and 38 electrons 52 neutrons.

Relative Atomic Mass

The relative atomic mass or atomic weight of an element is weighted average

of the mass of the isotopes in the naturally occurring element relative to the mass

of an atom of the carbon-12 isotopes which is taken to be exactly 12.

Relative atomic mass is unitless. It is the mass of a molecule (amu) divided by

1/12 the mass of one carbon-12 atom (amu).

Example 1.6.2

Naturally occurring silver is 51.84% silver-107 and 48.16% silver-109. Calculate

the relative atomic mass silver.

Solution:

Relative atomic mass = ( )109100

16.48()107

100

84.51

= 55.409 + 52.494

= 107.96 amu


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Exercise 1.6.2A

The atomic masses of 69Ga (60.4%) and 71Ga (39.60%) are 68.94 amu and

70.92 amu, respectively. Calculate the relative atomic mass for gallium.

Answer:

69.72

Exercise 1.6.2B

Naturally occurring chlorine is 75.78% 35Cl, which has an atomic mass of 34.969

amu, and 24.22% 37Cl, which has an atomic mass of 36.966 amu. Calculate the

average atomic mass (that is, the atomic weight) of chlorine.

Answer:

35.45 amu

Relative Molecular Mass

Relative molecular mass is also unitless. It is the mass of a molecule (amu)

divided by 1/12 the mass of one carbon-12 atom (amu). Atomic and molecularmasses can be measured with great accuracy with a mass spectrometry.

Figure 0-5


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Example 1.6.3

Calculate the relative molecular mass of H2SO4.

Solution:

Relative molecular mass H2SO4 = 2(H atomic mass) + 1(S atomic mass) + 4(O

atomic mass)

= 2(1) + 1(32) + 4(16)

= 98 amu

Mole concept

A mole (mol) is an amount of substance that contains as many elementary units(atoms, molecules and formula units) as there are atoms in exactly 12 gram of

the carbon-12 isotope. The actual number of elementary units in mole is called

Avogadros number, NAwhich is equal to 6.022 x 1023.

Examples 1.6.4

1 mol of copper metal, Cu, contains 6.02 x 1023of Cu atoms

1 mol of water, H2O contains 6.02x1023of H2O molecules

1 mol of MgCl2crystal contains 6.02x1023of formula units MgCl2

Exercise 1.6.4A

Calculate the number of Cu atoms in mol of copper

Exercise 1.6.4B

Calculate the number of

a) H2O molecules

b) H atoms

c) All the atoms in mol of water.


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Exercise 1.6.4C

Calculate the number of

a) formula units of AlF3

b) F-ions

c) All the ion in 0.02 mol of the compound AlF3

Molar Mass

Molar mass of a substance is the mass of 1 mol of that substance. The molar

mass is numerically equal to the atomic mass, molecular mass or formula mass,

but it is expressed in the unit g/mol.

The following relationships supply the conversion factors for the conversions

among mass in grams, amount in moles and number of elementary units.

Empirical and Molecular Formula

Percent composition or mass percent of a compound is the percent by mass of

each element the compound contains.

Empirical formulais the simplest possible whole number ratios of all the atoms

in a compound.

Mole of substance = mass of substance (gram)

Molar mass of substance (g/mol)

Percent compositions of element = n x molar mass of element

Molar mass of compound X 100Molar mass of compound X 100


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Molecular formula is the formula which shows the exact number of atoms or

each element in a molecule.

Example1.6.5

Calculate the percent composition of N atom in Ca(NO3)2

Solution:

Relative Molecular Mass = 40.08 + 2(14 + (16x3))

= 164.08

Percent composition of N = mass of N (g) x 100

Mass of Ca(NO3)2 (g)

= 2(14)g x 100

164.08 g

= 17.06%


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CHAPTER 2

PERIODIC TABLE OF ELEMENTS

1.7. Objectives

Upon completion of this chapter, student should have to:

1. Categorized elements in the period table into groups and periods based on

electrons configurations.

2. Categorized elements according to blocks of s, p, d and f.

3. Defined atomic radius, ionic radius, ionization energy, electrons affinity and

electronegativity and discussed their trends across the period and down the

group in the periodic table.

4. Discussed periodic trends in chemical properties across the period and down

the group.

4.1. Introduction

The periodic table is an arrangement of elements in the order of their increasing

atomic numbers to show that elements have related properties. Earlier table,

such as those of Dmitry Mandeleev (1869) and Lother Meyer (1869-1870) were

based on atomic weights which are measured as bulk properties and valency

relationship. At that time, the concept of atomic number was unknown. The main

purpose of the periodic table was:

a. Classification elements into groups with similar properties.

b. To predict the possibilities of new elements based on theor

properties.

The modern form of the periodic law states that properties of the elements are

the periodic function of their atomic numbers and the properties of the elements

depend on their electronic configuration.


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The modern periodic table consists of arrangements of elements in three broad

categories:-

a) metal

b) non metal

c) metalloids.

4.2. Periodic Classification of Elements

A modern periodic table (Figure ) consists of elements which are classified into

period (horizontal rows) and group (vertical rows). The periodsand groupsof

elements in the periodic table correlate closely with the electron configurations of

the elements concerned.

The period number is the same as the principle quantum number, n of the

electrons in the outermost principle shell. For example, all elements in the third

period have one or more electrons with n= 3 and none with a higher value of n.

The period begins with Na (1s2 2s2 2p6 3s1), and end with Ar (1s2 2s2 2p6 3s2

3p6). The next subshell to fill after 3p is 4s, so the next element after Ar is K

which is at the beginning of the fourth period has an electron configuration of 1s2

2s22p63s23p64s1

The periodic table groupnumber of an A group element (also called main group

or representative elements) is the same as the number of outershell electrons of

the elements. For example, all elements in Group IA have a single electron in an

s orbital of the outermost principle shell and all the noble gases except He in

Group 8A have 8 outer shell electrons.


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Periodic table is a systematic classification and arrangement of the elements

according to increasing atomic numbers. According to the type of subshell being

filled, the elements can be divided into categories- the representative elements,

the noble gases, the transition elements, the lanthanides and the actinides.

The representative elements (or the main group elements) are the elemets in

Group IA through 7A, all of which have incompletely filled s and p subshell of

highest principle quantum number.

Elements in the same group of the periodic table have similar valence shell

electron configurations because they have the same number of valence

electrons. The similarity of the outer electrons configurations makes the elements

in the same group show similar chemical properties. The number of valence

electrons (outer shell electrons) in an element represents the group number of

the element in the periodic table.

Periodic table

Group

(Vertical columns)

Period

(Horizontal rows)

A

Representative elementor main

group elements (8 groups)

B

Transition metal


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The period number of the element is the principle quantum number of the

outermost principle energy shell in an atom.

Some groups are given special names as shown:

Group Special Name

IA

IIA

VIIA

VIIIA

Alkali meal

Alkali earth metals

Halogen

Noble gases

Generally, metal atoms have small numbers of electrons in their valence shells.

Except for hydrogen and helium, all s block elements (group I and II) are metals.

All d and f block elements are metals. A few of the p block elements like Al, Ga,

Pb, Sn, In and Bi are also metals.

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