Elements and Periodic Table

Elements and Periodic TableChapter 3

Unit- Introduction to chemistryMrs. Castro

INTRODUCTION TO ATOMS

Lesson 1Pages 72 – 79

Introduction to atoms

Atomic Theory This is the theory that explain with details the

component of the atoms and their organization. Grew as a series of models that developed from

experimental evidence. As more evidence was collected, the theory and models were revised.


Democritus – Greek philosopher – 430 B.C. Proposed that matter was formed of small pieces that

could not be cut into smaller parts. He called the particles atoms – means “uncuttable” Atoms is the smaller particles that still can be

consider an element. 1600 – people did experiments and the theory

began to take shape.


John Dalton – English chemist Dalton’s Atomic Theory:

All elements consist of atoms that cannot be divided. All atoms of the same element are exactly the same

and have the same mass. Atoms of different elements are different and have different mass.

An atom of one element cannot be changed into an atom of a different element by a chemical reaction.

Compounds are formed when atoms of more than one element combine in a specific ratio.


J.J. Thomson – 1897 Discovered that the atoms contain negatively charged

particles called electrons. He reasoned that atoms must also contain some sort

of positive charge, balance the negative charge of the electrons.


Ernest Rutherford – 1911 Suggested that the atoms is mostly empty space but

has a positive charge at its center (nucleus). He called the positively charged particles in an atom’s

nucleus protons.


Niels Bohrs – 1913- Danish scientist Suggested that the electrons are found only in

specific orbits around the nucleus. Each possible electron orbit in Bohr’s model has a

fixed energy.


Cloud Model – 1920 Electron are moved rapidly within a cloudlike region

around the nucleus. An electron’s movement is related to its energy level,

or the specific amount of energy it has. Electrons at different energy levels are likely to be

found in different places.


James Chadwick – 1932 – English scientist Found a no electric charge particle. He called

neutron.

Modern model of atom At the center of the atom is a tiny, dense nucleus

containing protons and neutrons. Surrounding the nucleus is a cloudlike region of moving electrons.


Model of Modern Atom:


Important details:1. Proton = p+, positive charge2. Electron = e-, negative charge3. Neutron = n, no charge4. The number of protons equals the number of

electrons. As a result, the positive charge is equals to the negative charge.

5. The charge balance, make the atom neutral.6. Neutrons don’t affect the charge of an atom

because they have a charge of zero.


Answer the following questions:1. What is in the center of an atom?2. What particles we found inside the center of an

atom?3. Where the electrons are found?4. Why the atom is neutral?5. What is the effect of the neutrons on the charge

of an atom?6. If the atom has 8 p+, how many e- does it

have? What is the atom’s charge?


Atomic mass (Z) = n + p+ The mass of the atom is in the nucleus.

Atomic number (A) = p+ Atomic number = e-

Answer:1. Z = 2. A = 3. Element name =4. Element symbol =


Identify Z, A and element name, electron’s quantity and proton’s quantity :

Z = atomic mass

A = atomic number

Hydrogen

e- = 1p+ = 1


Remember: Atomic mass (Z) = n + p+

From this equation: n = p+ - atomic mass (Z) Atomic number (A) = p+ = e-


Complete the following table:

Atom’s Name

Symbol Atomic number

Atomic mass

e- p+ n

52 128

Sr 38 50

103 45

Pb 82 125

209 126

Zr 40 51


AnswerAtom Name

Symbol Atomic number

Atomic mass

e- p+ n

Tellurium Te 52 128 52 52 76

Strontium Sr 38 88 38 38 50

Rhodium Rh 45 103 45 45 58

Lead Pb 82 207 82 82 125

Bismuth Bi 83 209 83 83 126

Zirconium Zr 40 91 40 40 51

Introduction to atoms Isotopes

Atoms with the same number of protons and different numbers of neutrons.

Isotopes are identified by its mass number or atomic mass.

Examples:Carbon atomic number is 6. Protons = 6

C-12 C-13 C-14n=12-6 n=13-6 n=14-6 6 7 8Atom Isotope Isotope


Fill the blanks:1. The ______ is the very small, dense center

of an atom.2. The positively charged particle of an atom

is called ___________.3. A particle with no charge is ________.4. An _______ is the particle of an atom that

moves rapidly in the cloudlike region around the nucleus.

nucleus

proton

neutron

electron


5. The ___________ tells the number of protons in the nucleus of every atom of an element.

6. Atoms of the same element that have the same number of protons but diffrent numbers of neutrons are called _________.

7. The sum of p+ and n in the nucleus of the atom is the _________.

Atomic number

isotopes

Atomic mass


Read pages 73 to 79.Perform all the excises.

ORGANIZING THE ELEMENTS

Lesson 2Pages 80 - 87

Organizing the elements 1860 – 63 elements were discovered. Dmitri Mendeleev discovered a set of patterns that

applied to all the elements. He noticed that the pattern of properties appeared

when he arranged the elements in order of increasing atomic mass.

He found that the properties of the elements repeated.

Properties studies: melting point, density , color and atomic mass.

Organizing the elements

Mendeleev created the first Periodic Table in 1869.

This is a table in which is an arrangement of elements showing the repeating pattern.

Organizing the elements As scientists discovered new elements and

learned more about atomic structure, the periodic table changed.

At the present, the Periodic Table is arranged in order of increasing atomic number.

It is now know that the number of protons in the nucleus, given by the atomic number, determines the chemical properties of an element.


Periodic Table Information;1. Atomic number - # p+ and e-2. Chemical symbol

1. Is one or two letters. First letter is capital letter, second letter is lowercase letter.

2. Is an abbreviation of the element’s name in English.3. Some of them, have symbols that are abbreviations

of their Latin names.3. Atomic mass – n + p+

Organizing the elements Fing the element’s name or symbol.

Element’ name SymbolTin

Na

Barium

Br

Galium

C

Neon

B

Nickel

Al

Organizing the elements Fing the element’s name or symbol.

Element’ name SymbolTin Sn

Sodium Na

Barium Ba

Bromine Br

Galium Ga

Carbon C

Neon Ne

Boro B

Nickel Ni

Aluminum Al


Find the element, identified by the atomic number, complete the information:

Atomic Number

Name Symbol Atomic mass

p+ and e-

n

9

12

79

17

53


Find the element, identified by the atomic number, complete the information:

Atomic Number

Name Symbol Atomic mass

p+ and e- n

9 Fluorine F 19 9 10

12 Magnesium Mg 24 12 12

79 Gold Au 197 79 118

17 Chlorine Cl 35 17 18

53 Iodine I 127 53 74


Find your name using the element’s symbols Example: CASTRO

C – arbon As – Arsenic Tr - ________ O - Oxygen

Organizing the elements An element’s properties can be predicted from their location

in the Periodic Table. Period – rows - Are 7 Group or family – column – Are 18 – Each of them have

different name and properties.Find the name of the element using the period andgroup:Period Group Name 3 14 2 17 5 18 4 8

METALS

Lesson 3Pages 88 – 95

Metals

Are the majority of elements. Properties:

1. Luster – shiny2. Malleability – material is one that can be

hammered or rolled into flat sheets or other shapes.

3. Ductile – material is one that can be pulled out, or drawn into long wires.

4. Thermal conductivity – transfer heat.5. Electrical conductivity – carry electric current.

Metals

6. Reactivity – react with other substance by loosing electrons to other atoms.

7. Corrosion – deterioration due to chemical reaction in the environment.

Metal Classification

I. Alkali Metals (metales alcalinos) Group 1 Most reactive. They are never found as uncombined elements

in nature. Always are in compound. Some of them are so soft you can cut them with

a plastic knife. Low densities and melting point.


II. Alkaline Earth metals (metales alcalinotérreos)

Group 2 Harder and denser. Melt at high temperature than alkaline metals. Very reactive, but not as the alkaline. Never found uncombined in nature.


III. Transition metals Groups 3 to 12 Most are hard and shiny solids. Mercury is liquid at temperature room. Except Mercury, they have high melting point

and densities. Good conductors of heat and electric current. Very malleable. Are less reactive than the groups 1 and 2.


IV. Metals in mixed groups Only some of the elements on groups 13

through 17 are metals. They are: Al, Ga, In, Sn, Tl, Pb, Bi, and Po.

V. Lanthanides and Actinides (Lantánidos y Actínidos)

Top row after the main part of the PT.- Lanthanides

Below the Lanthanides – Actinides Not found in nature but are artificially in laboratories.


VI. Transuranium Elements (elmentos transuránicos)

Elements follow uranium (U). These elements are made or synthesized, when nuclear particles are forced to crash into one another.

Elements with atomic number greater than 111 do not yet have permanent names or symbols. In the future, scientists around the world will agree on permanent names and symbols for these elements.

Metals

Let made some excises

NONMETALS AND METALLOIDS

Lesson 4Pages 96 - 105

Nonmetals and metalloids

Nonmetals: Elements that lacks most of the properties of a

metal. Except for H, the non metals are found on the

right side of the PT. Properties:

Poor conductors of electric current and heat. Solid nonmetals are dull and brittle. Lower densities that metals. Most are gases at room temperature.


Properties cont. Usually gain or share electrons when they react with

other atoms. The families that containing nonmetals include

the carbon family, nitrogen family, oxygen family, halogen family, the noble gases and hydrogen.

Complete blue table on page 99.


Carbon family: Group 14 Only Carbon is nonmetal. It is an important element for life.

Nitrogen family: Group 15 Nitrogen and Phosphorus are nonmetals.

Nonmetals and metalloids Oxygen family:

Group 16 Oxygen, sulfur and selenium are nonmetals.

Halogen Family: Group 17 Fluorine, chlorine, Bromine and iodine are

nonmetals. Astatine (At) are rare and properties are unknown. Are vary reactive. Fluorine are the most reactive.

Nonmetals and metalloids Noble gases:

Group 18 Do not form compounds because do not gain, lose or

share electrons. Nonreactive.

Hydrogen: The element with the simplest atom. The properties are very different from those of the other

element, so it cannot be grouped in with a family. Is rarely found on earth as a pure element. It found

combined with oxygen as water.


Metalloids: Are between metals and nonmetals. They have some properties of metals and some

form nonmetals. Are solids at room temperature. Brittle, hard and somewhat reactive. Most common is Silicon. Is in sand. The conductivy of electric current , depend on

temperature, exposure to light or presence of impurities. Some of them are semiconductors.

Practice

First find the name and then classify the following elements in metals, nonmetals and metalloids:1. Si 2.Rh3. Br 4. Eu5. Co 6. F7. Cs 8. Pb9.Sb 10. Ag

Fun Practice

PERFORM ALIEN PERIODIC TABLE ON PAGES 104 - 105

Period Table Exercise – See teacher for instructions

Review and assessmentPages 115 -116

END

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