Dear Student,

the postulates of Bohr's atomic model are:-

• In an atom, the electrons, negatively charged, revolve around the positively charged nucleus in a definitive circular path known as the orbit or shells
• Each of the orbits or shells has a fixed energy and these circular orbits are called as orbital shells
• The energy levels are represented by an integer (n=1, 2, 3…) which is called as the quantum number. This range of quantum number begins from the  nucleus side where n=1 having the lowest energy level. The orbits n=1, 2, 3, 4… are assigned as K, L, M, N…. shells and when an electron attains it's lowest energy level, it is known to be in the ground state.
• The electrons of an atom move from a lower energy level to a higher energy level by gaining the required energy and an electron moves from a higher energy level to a lower energy by losing some energy.

Boh'r proposed this atomic model as a modification to the Rutherford's model. Rutherford had stated that nucleus is surrounded by negatively charged electrons but Bohr stated by explaining electrons and their energy levels.