There are three types of energy bands present in solids including conduction band, valence band and forbidden band. The energy band formed by the electrons with maximum energy in an atom is called conduction band. The electrons of this band contribute to the conductivity of heat and electricity. That is why these electrons are also called conduction electrons. The energy band formed by the filled energy states is called valence band. The electrons in the this band have minimum energy. The energy gap present between the valance and conduction band is called forbidden energy gap.
Substance having large conductivity and negligible resistivity are called conductors for example, gold, silver, copper etc. Conductors have a very large conduction band because of their conductivity. In conductors, valence band is very small (almost empty). Forbidden band does not exist in conductors. The valence band and conduction band overlapped each other. It means some of the electrons have energies which lie simultaneously in valence band and conduction band. Moreover, on the average there are 1023 free electrons per centimeter cube in a conductor.
Substance having large conductivity and negligible resistivity are called conductors for example, gold, silver, copper etc. Conductors have a very large conduction band because of their conductivity. In conductors, valence band is very small (almost empty). Forbidden band does not exist in conductors. The valence band and conduction band overlapped each other. It means some of the electrons have energies which lie simultaneously in valence band and conduction band. Moreover, on the average there are 1023 free electrons per centimeter cube in a conductor.
