The main postulates of Bohr’s atomic model are:-

•An atom consists of a massive
positively charged nucleus. The electrons are moving around the nucleus.
The electrons are moving around nucleus in certain fixed circular orbits without radiating energy.
These non-radiating orbits are known as stationary states.

• Each of the fixed circular orbits or stationary states is associated with the definite amount of energy.
Hence stationary states are also called energy levels.
The energies of the energy levels increases with increase in distance from the nucleus.

Energy levels are designated with the letters

K, L,M,N…. Or 1 , 2,3,…

Those letters designated with Energy Levels

The electrons will move/ jump from lower energy state to higher energy ( excited state ) state , when required amount of energy is absorbed and to move from higher to lower ,

energy ( ground state ) is emitted.

• Energy is emitted or absorbed discontinuously in the forms  quantas or small packets only during transitions between two stationary states .
The frequency of radition absorbed or emitted when transition occurs between two stationary states that differ in energy ∆E , is given by

ν = ∆E/h

      = E₂ – E₁

where E₂ and E₁ are the energies of lower and higher levels.

• The angular momentum of an electron is quantised.
Given stationary state, it can be expressed as ,
mvr = nh/2π

Bohr’s Atomic model was widely accepted and based on this postulates many phenomena like Hydrogen Spectrum is explained