State and explain Bohr's postulates for hydrogen atom.

Explanation

Bohr gave following three postulates for hydrogen atom:
1. An electron revolves round the nucleus in certain specified circular orbits in which it does not radiate energy. The centripetal force required for uniform circular motion in such a stationary orbit is provided by electrostatic force of attraction. Thus, `(m v_(n)^(2))/(r_(n)) = (1)/(4 pi in_(0)) .(e^(2))/(r_(n)^(2))" "......(i)`
2.For an orbit to be stationary (or non - radiating ) , the angular momentum of the electron must be an integer multiple of `(h)/(2pi)` where h is the Planck .s contant . Thus
`L_(n) = m v_(n) r_(n) = (nh)/(2pi)" ".......(ii)`
3. Whenever an electron shift from one of its specified non - radiating orbit to another such orbit , it emits /absorbs a photon whose energy is equal to the energy difference between the initial and final states . Thus .
`E_(i) = E_(f)= hv = (hc)/(lambda)" "............(iii)`