Question

 Explain the energy bands in solids. 
 

Hint:

The nature of the energy gap between bands determines the electrical conductivity of a material.

Answer 1

Energy bands in solids refer to continuous ranges of energy that electrons in a solid can occupy. The primary energy bands are the valence band, conduction band, and forbidden energy gap.
1. Valence Band: The energy band filled with the highest energy electrons in a solid.
2. Conduction Band: The energy band above the valence band where electrons can move freely, contributing to conductivity.
3. Forbidden Energy Gap: The region between the valence band and conduction band where no electron can exist. Classification of solids based on band theory:
- Conductors: Overlapping valence and conduction bands.
- Semiconductors: Small energy gap between valence and conduction bands.
- Insulators: Large energy gap, preventing electron movement.