Distribution of electrons in various shells.

Learning Objective:

How are Electrons Distributed in Different Orbits (Shells)?The distribution of electrons into different orbits of an atom was suggested by Bohr and Bury.

The energy of the K shell is the least while those of L, M, N and O shells increases progressively. We also know that any system that has least energy is the most stable.1st energy level is K shell 2nd energy level is L shell 3rd energy level is M shell 4th energy level is N shell and so on

Bohr and Bury Scheme - Important Rules

Maximum number of electrons that can be accommodated in a shell is given by 2n2 where n = shell number

For 1st energy level, n = 1Maximum number of electrons in 1st energy level = 2n22 x (1) 2 = 2

For 2nd energy level n = 2Maximum number of electrons in the 2nd energy level = 2n22 x 22 = 2 x 4 = 8

For 3rd energy level n = 3Maximum number of electrons in the 3rd energy level = 2n2= 2x(3) 2= 2 x 9 = 18

For 4th energy level n = 4 Maximum number of electrons in the 4th energy level = 2n2= 2x(4) 2= 2x16 = 32

Sl.No Electron Shell Maximum Capacity

1 K Shell 2 electrons

2 L Shell 8 electrons

3 M shell 18 electrons

4 N shell 32 electrons

Bohr and Bury Scheme - Important Rules

Electronic Configurations of Some Important Elements

Geometric Representation of Atomic Structure

Below are the examples on Geometric Representation of Atomic StructureExample: 1

 24 Mg12

Steps: 

•The first 2 electrons will go to the 1st shell = K Shell (2n2)•The next shell L takes a maximum of 8 electrons (2n2)•In this way 2 + 8 = 10 electrons have been accommodated. The next 2 electrons go to the M Shell.

Atomic structures of the First Twenty Elements