Energy band gap of an insulating material is:

Explanation-

Valence band-

The electrons in the outermost shell are known as valence electrons. These valence electrons contain a series of energy levels and form an energy band known as valence band. The valence band has the highest occupied energy.

Conduction band-

The valence electrons are not tightly held to the nucleus due to which a few of these valence electrons leave the outermost orbit even at room temperature and become free electrons.

The free electrons conduct current in conductors and are therefore known as conduction electrons. The conduction band is one that contains conduction electrons and has the lowest occupied energy levels.

Forbidden Energy gap-

The gap between the valence band and the conduction band is referred to as forbidden gap.

Insulators-

Glass and wood are examples of the insulator. These substances do not allow electricity to pass through them. They have high resistivity and very low conductivity.

The energy gap in the insulator is very high up to 7eV.

The material cannot conduct because the movement of the electrons from the valence band to the conduction band is not possible.