Question

Difference between metal insulator and semiconductor on the basis of band theory

Answer 1

Distinguish between metals, insulators and semiconductors on the basis of their energy bands. Metals: In metals, either the conduction band is partially filled or valence band is partially empty. ... The conduction band and the valence band overlap each other ( there is no forbidden energy gap) in metals.

Answer 2

Metals: Band Gap - either there is no energy gap b/w conduction and valence band or they both overlap each other

Insulators: Valence band is completely filled - conduction band is completely empty and energy gap is quite large that small energy from other source cannot overcome it - $E_g> 3eV$

Semiconductors: Valence band totally filled - conduction band empty but energy gap is very small - $E_g< 3eV$