Bohr.s atomic model.

Explanation

Nells Bohr (1913) was the first to explain quqntitatively the general features of hydrogen atom structure and tis spectrum.
Pitulates of model:
(i) The electron is the hydrogen atom can move around the nucleus in a circular path called orbits stationary states or allowed energy states . These orbits are arrangest concentrically around the nucleus.
(ii) The energy of an electron in the orbit does not change with time However the electron will move from a lower stationary state to a higher stationary state when required or energy is emitted when electron moves does not take place in a continuous change
(iii) The frequency of radiation absorbed or emitted when transition occurs between two stationary states that differ in energy by
Where `E_(1)` and `E_(2)` are the energies of lower and higher allowed energy states respectively this expression is commonly known as bohr frequency rule
Thus an electron can move only in those orbits for which its angular momentum is integral multiple of `((h)/( 2pi))` that is why only certain fixed orbits are allowed.