For solid materials, the electron energy band that contains the valence electrons.
The valence band is the highest range of electron energies in which electrons are normally present at absolute zero temperature. The valence electrons are bound to individual atoms, as opposed to conduction electrons (found in conductors and semiconductors), which can move freely within the atomic lattice of the material. On a graph of the electronic band structure of a material, the valence band is located below the conduction band, separated from it in insulators and semiconductors by a band gap. In metals, the conduction band has no energy gap separating it from the valence band.