Question

Which of the following statements are correct regarding band theory of metallic bond ?

• A. Overlapping of conduction & valence band occurs in semiconductors
• B. Valence band is empty or half filled in metal
• C. Energy gap between conduction and valence band is very less in non-conductors
• D. Conduction band is empty in metal

Answer 1

The correct option is D Conduction band is empty in metal

Conduction band is made up of those orbitals which are unoccupied by electrons either in valence shell or higher unoccupied shell. Thus, the orbitals of the conduction band are empty. For sodium, after 3s, 3p is empty so it forms a conduction band.
Valence Band is made up of those valence shell orbitals which have electrons in them. For example, a sodium valence band is made up of $3s^1$ orbital. Valence band is never empty or half filled for a metal.
The energy gap between conduction and valence band in semiconductors is more than metal and largest in non-conductors. So overlapping of conduction and valence band is not feasible in semiconductors and non-conductors.