Question

state bohr's postulates and explain them

Answer 1

Bohr's postulates :
1.electron revolve around the nucleus in a circular orbit.
2.as the electron move from one orbit to other it gains or loss energy.
3.as the electron remains in a particular orbit it neither loss or gain energy.
4.the shells are called as stationary states.

Answer 2

There may be variations of the statements and number of postulates. the meaning is important.

Niels Bohr postulated (like assumptions) the following :

1.  The Electron revolves around the nucleus in circular orbits.
2.  The orbit of electrons can take only special values of radius. In these orbits
     electrons do not radiate energy. These are called stationary orbits.
3.  The energy of the atom has a definite value in a stationary orbit. When an
     electron jumps from one orbit (energy level E2) to another orbit of lower energy
     E1, it emits a photon of radiation, with energy E2 - E1.
              E2 - E1 = h n
4.  In stationary orbits, the angular momentum L of the electron about the nucleus is an integral multiple of h/2π.