The postulates of Bohr's model of an atom are
1. Electrons revolve around the nucleus of an atom in a certain definite path called the Orbit or stationary state of the shell.
2. The shells are having different energy levels denoted as K, L, M, N.
3. As long as the electron remains in an orbit, it neither absorbs nor emits energy.
4. The electron can move only in that orbit in which angular momentum is quantized, i.e., the angular momentum of the electron is an integral multiple of $$\dfrac{h}{2 \pi}$$.