The following diagram represents the electron population of the bands of MO energy levels for elemental silicon:
(a) Identify the valence band, conduction band, and band gap.

Key Concepts

Valence Band

The valence band is the highest energy band that is fully occupied by electrons at absolute zero temperature. In semiconductors like silicon, it contains the electrons that are involved in bonding and determines the electrical properties of the material. When electrons in the valence band gain enough energy, they can move to the conduction band, allowing for electrical conduction.

Conduction Band

The conduction band is the range of energy levels that electrons can occupy when they are free to move within a material, contributing to electrical conductivity. In semiconductors, this band is typically empty at absolute zero but can be populated by electrons that have gained sufficient energy, such as from thermal excitation or photon absorption. The ability of electrons to move in this band is crucial for the conduction of electricity.

Band Gap

The band gap is the energy difference between the valence band and the conduction band in a semiconductor. It represents the minimum energy required for an electron to transition from the valence band to the conduction band. The size of the band gap determines the electrical and optical properties of the material, influencing its conductivity and the wavelengths of light it can absorb or emit.