This theory was put forward by Neil’s Bohr in 1913 in which the defects ofRutherfordatomic model are removed.
Following are the postulates of Bohr’s atomic theory;
i. Electrons are moving round the nucleus in fixed path of fixed energy called orbits or energy levels.
ii. As long as any electron is moving in an energy level it neither loses nor gains energy.
iii. When any electron jumps from one orbit to another, it either loses or gain energy.
iv. The amount of energy loses or gain by electron is equal to the difference of energy of two energy levels i.e.
∆E = E2 – E1
∆υ = E2 – E1
h = Plank’s constant
υ = frequency of energy
E1 = energy of 1st orbit
E2 = energy of 2nd orbit
v. Orbit is present round the nucleus at fix distances where the product of momentum of electron and circumference of circle must equal to either of Plank’s constant or its integral multiple.
(mv)(2πr) = nh
mvr = nh/2π
So angular momentum must equal to integral multiple of h / 2π