structure of atom

1. ARMY PUBLIC SCHOOL, RAKHMUTHI
UNIT: STRUCTURE OF ATOM ( CHEMISTRY) class : 9th
( lecture2)
Date: 15 oct- 2020 SUBJECT INCHARGE: MISS RITIMA
ELECTRON DISTRIBUTION IN SHELL:
The distribution of electrons into different orbits of an atom was suggested by Bohr and Bury (Bohr-Bury scheme).
Rules are followed for writing the number of electrons in different energy levels or shells are:
1. The maximumnumberof electronspresentinashell isgivenbythe formula 2n2
(where ‘n’ is the orbit number).
First orbit or K-shell will be = 2 × 12
= 2,
Second orbit or L-shell will be = 2 × 22
= 8
Third orbit or M-shell will be = 2 × 32
= 18
Fourth orbit or N-shell will be = 2 × 42
= 32.
2. The maximum number of electrons that can be accommodated in the outermost orbit is 8.
3. Electronsare not accommodatedina givenshell,unlessthe innershellsare filled.Thatis, the shells are filled in
a step-wise manner.
Schematic atomic structure of the first eighteen elements