SUBATOMIC PARTICLES OF ATOM

The Neutrons

 J. Chadwick discovered that there is another sub-atomic particle present in the atom. This particle carries no charge and is known as a Neutron. Therefore, we can conclude that atom consists of three types of particles -

Electrons

which carry a negative charge

Protons

which carry a positive charge

Neutrons

they are neutral 

The distribution of electrons in different shells or orbits

  • If Orbit number = n
  • Then number of electrons present in an Orbit = 2n2
  • So, for n =1
  • Maximum electrons present in shell – K = 2 * (1)2 = 2
  • The outermost shell can contain at most 8 electrons.
  • The shells in an atom are filled in sequence.
  • Thus, until the inner shells of an atom are filled completely the outer shells cannot contain any electrons.

Valency-

  • The combining capacity of an atom of an element to form a chemical bond is called its valency.
  • The electrons present in outermost shell of an atom are called as valence electrons.
  • Valency of a metal=Number of Valence electrons
  • Valency of a non-metal=8-Number of valence electrons

For Example
Sodium (Z=12)

  • The electronic configuration of sodium is
  • K L M
  • 281
  • Valence Electrons =1
  • Valency - 1 

Atomic number

Name of element

Symbol

Valency

Atomic number

Name of element

Symbol

Valency

1

Hydrogen

1

11

Sodium

1

2

Helium

0

12

Magnesium

2

3

Lithium

1

13

Aluminium

3

4

Beryllium

2

14

Silicon

4

5

Boron

3

15

Phosphorous

3,5

6

Carbon

4

16

Sulphur

2

7

Nitrogen

3

17

Chlorine

1

8

Oxygen

2

18

Argon

0

9

Fluorine

1

19

Potassium

1

10

Neon

0

20

Calcium

2