Let me test my theory through examining the hydrogen atoms!
Prior to Bohr's atomic model, the motion of the electrons presented in the Rutherford model would be unstable since the electrons moving in planetary movements would release electromagnetic radiation, therefore colliding into the nucleus .
If the electrons move in circular orbits with discrete radii, the wavelength of the light emitted of the hydrogen atoms would also be discrete.
Moreover, as the electrons emit the energy, the wavelength of the radiation would vary, forming a smooth light spectrum yet the actual light spectrum is not smooth and has discrete units within .
When the electrons absorb energy from the photon, it will move to the outer shell. In reverse, if the electron moves from the outer level to the inner level, the electrons would emit the photons.
To amend Rutherford's atomic model, Bohr proposed his atomic theory: electrons moved in different layers of fixed energy and size. Bohr built his model based on the light emitted by real hydrogen atoms .
As Bohr proposed, the energy lost during the transition of the elections is about the same as the energy of the emitted light of the hydrogen atoms, which explains the spectra observed. Bohr drew the conclusion that electrons move in different layers of orbit and cannot be found in between the layers.