Consider the figure from section "Electrical conductivity":https://en.wikipedia.org/wiki/Valence_and_conduction_bands I understand that below the Fermi level, we have bands of allowed energy separated by band gaps. Then, we have the Fermi level. Then we have the conduction band. My question. Above the Fermi level I see band gaps. Is this the case? I thought that the free electrons can have any energy that they want. A second question. I know that below the Fermi level, the energies of the electrons are quantified. Thus, we say "continuous" bands. But actually these bands contain discrete energies very close one to another. Is it the same for the conduction band? Or when the electron is found in the conduction band, can it have any energy that he wants? Or its energy is still quantified as a free electron?