Write any two distinguishing features between Insulators , Metals and semiconductors and insulators an the basis of energy band diagrams.

Explanation

Insulators :
(i) The valence band and the conduction band are separated by a large energy gap.
(ii) The forbidden energy gap is approximately 6 eV in insulators.
(iii) The gap is very large that electrons from valence band connot move into conduction band even on the application of strong external electric field or the increase in temperature.
Metals
(i) In metals, the valence band and conduction band overlap.
(ii) Hence, electrons can move freely into the conduction band which results in a large number of free electrons in the conduction band.
Semiconductors
(i) In semiconductors, there exists a narrow forbidden energy gap `(E_(g) lt3eV)` between the valence band and the conduction band.
(ii) Free electrons are small in number, the conductivity of the semiconductors is not as high as that of the conductors.