Writer Bohr's postulates for the hydrogen atom model.

Explanation

First Postulate : Electron revolves round the nucleus in discrete circular orbits called stationary orbits without emission of radiant enerty. These orbits are called stable orbits or non-radiating orbits.
Second postulate : Electrons revolve around nucleus only in such orbits for which the angular momentum is some integral multiple of `(h//2pi)`
Third Postulate : When an electron makes a transition from one of its non-radiating orbits to another of lower energy difference between the two states. The frequency of the emitted photon is then given by, `hv = E_(i) - E_(f)`.