The energy gap between the valence band and the conduction band is largest in
- A. a conductor
- B. a semiconductor
- C. an insulator
- D. all three equally
Explanation
An insulator has a gap of several electron volts, far more than thermal energy can supply, so almost no electrons reach the conduction band. A semiconductor's gap is about 1 eV, small enough for a useful number to cross, and in a conductor the bands overlap so there is effectively no gap at all. This single picture explains the huge range of electrical behaviour in solids.