Valence Energy band: In this energy band there are large no of free electrons available. Filling of the valence band can be partial or complete. These bands never get empty.
The major disadvantage of the electrons present in this band is that these electrons are unable to attain energy from any external source of electric field.
Conduction Energy Band: The density of the electrons is very few. As compared to the electrons present in the valence energy bands, these electrons can gain energy from the external field of electric field.
Forbidden Energy Band: Electrons are absent in this energy band. Some little amount of energy is needed for electron shifting to conduction band from valence band. This type of gap is known as band gap. Symbol used to represent band gap is Eg.
