Energy Bands in Conductors

Define Energy Bands

Energy bands in solids are ranges of energy levels that electrons can occupy. These bands form when atoms come together to form a solid, and their individual atomic energy levels interact and split into closely spaced energy levels.

Types of Energy Bands:

Valence Band:

• This is the outermost filled energy band at absolute zero temperature
• It contains the valence electrons which are responsible for chemical bonding
• These electrons are normally bound to specific atoms and cannot move freely
• In an isolated atom, these would be the outermost shell electrons
• if filled, it cannot allow movement of electrons
• if partially filled or half filled, it allows movement of electrons

Conduction Band:

• This is the energy band above the valence band
• It contains free electrons that can move through the material
• These electrons contribute to electrical conduction
• This band may be empty or partially filled

Band Gap:

• This is the energy difference between the top of the valence band and bottom of the conduction band
• also named as energy barrier
• The size of the band gap determines how easily electrons can move from valence band to conduction band i.e. how easily electrons can be free.
• Low energy band gap means higher conductivity, higher energy gap means lower conductivity.

Energy Band Diagram