Quantum nature of radiations by atoms

When an electron is excited, it will jump from its electron shell to an outer transitory shell, because of the density differences between the space matter in the inner and outer regions of the atom. I.e. when an electron oscillates in its shell, for every oscillation towards the direction of the nucleus, the high-density space matter in the inner region of the atom expels the electron to a low-density outer region. Since the excitation of an atomic electron is purely because of the excitation of its shell, as the electron jumps from its excited shell to an outer transitory shell, the electron will lose its excitation simultaneously. This is the reason for the quantum or photon nature of radiations by an atom.