Conduction Band
Definition and meaning of Conduction Band in chemistry.
Conduction band is the range of electron energy levels in a solid that lies immediately above the valence band and is empty, or only partially filled, allowing the electrons within it to move freely and carry electric current.
In more detail
In band theory, the overlapping atomic orbitals of a crystalline solid merge into continuous bands of allowed energy separated by forbidden gaps. Electrons confined to the valence band are bound to atoms and cannot conduct, but once an electron is promoted into the conduction band, by thermal energy, absorbed light, or doping, it becomes delocalized across the lattice and responds to an applied electric field. The energy gap separating the two bands determines electrical behavior: overlapping or partially filled bands give a conductor, a small gap gives a semiconductor, and a large gap gives an insulator.
Key facts
| Field | Physical Chemistry |
|---|---|
| Location | Directly above the valence band |
| Typical band gap (silicon) | ~1.1 eV |
| Governs | Electrical conductivity of solids |
Silicon has a band gap of about 1.1 eV; at room temperature, thermal energy excites a small fraction of valence-band electrons across this gap into the conduction band, producing silicon's intrinsic semiconducting conductivity and leaving behind mobile electron holes in the valence band.
Frequently asked questions
What distinguishes the conduction band from the valence band?
The valence band holds electrons bound to atoms in bonding states, while the conduction band is a higher-energy range where electrons are delocalized and free to move, enabling current flow.
How does the conduction band explain conductors, semiconductors, and insulators?
The classification depends on the band gap: conductors have overlapping or partially filled valence and conduction bands, semiconductors have a small gap electrons can cross thermally or optically, and insulators have a gap too large for electrons to cross under normal conditions.