Sommerfeld’s atomic model

To explain this, Sommerfeld suggested that it is not necessary that all the electrons of the same orbit have the same energy, the energies of some electrons of the same orbit may be different from the energies of the other electrons. In other words, the main energy levels are divided into sub-energy levels. It is not necessary that all the electrons of the same orbit rotate on the same circular path, rather some of them can move on the elliptical paths. The nucleus of an atom is at one of the two foci of elliptical orbitals. <a href="https://srjng88.medium.com/sommerfelds-atomic-model-9baf47ccd020">Website</a>