CBSE Class 9 Answered

In 1913 Niels Henrik Bohr published his new theory of the atoms constitution. Just like Rutherford he assumed that electrons circulate around the nucleus. But had the three completely new ideas:

1. There are some orbits called by him the stationery ones, where the moving electrons don't emit energy.
2. Each emission or absorption of radiation energy represents the electron transition from the one stationery orbit to the another. The radiation emitted during such transition homogeneous and its frequency is given by the formula hv = E₁-E₂, where h is the Planck constant, E₁ and E₂ are the energies in the two stationary states of the system.
3. The laws of mechanics describ the dynamic equilibrium of the electrons in stationery states but do not describe the situation of the electron transition from the one stationery orbit to the another.