chapter 2.3 and 2.4

2.3 Isotopes and Their Importance

Isotopes:

Atoms of the same element with same

number of proton but different number of

neutrons.

OR

Atoms of the same element with same

proton number but different nucleon

number.

Example of elements with isotopes:

Hydrogen

H1

1 H2

1 H3

1

Hydrogen-1 Hydrogen-3Hydrogen-2

Chlorine

Cl35

17 Cl37

17

Chlorine-35 Chlorine-37

Uses of isotopes in our daily lives

In the medical field:

Cobalt-60

Used in radiotherapy for the treatment of cancer

Iodine-131

Treatment of thyroid gland

In the argiculture field:

Phosphorus-32

Study the metabolism of phosphorus in plants

Gamma ray of cobalt-60

Used to destroy bacteria in food

Uses of isotopes in our daily lives

in industrial field:

Sodium-24

Used detect leakages in pipes

In archeology field:

Carbon-14

To estimate the age of fossils and artifacts

2.4 The Electronic Structure of an Atom

The first shell : 2 electrons

The second shell : 8 electrons

The third shell : 8 electrons

Nucleus

Example:

Chlorine atom

Proton number of 17

Hence, chlorine atom has 17 electrons

Electron arrangement:

2.8.7

Valence electrons

The electrons in the outermost occupied

shell

Outermost

occupied shell

Valence electron