Conduction electrons

Valence Band:-The band of energy occupied by the valence electrons is called the valence band. The valence band is the highest occupied band.

Conduction Band:-The conduction band is normally empty and may be defined as the lowest unfilled energy band. In the conduction band, electrons can move freely and are generally called conduction electrons.

In solid-state physics, the valence band and conduction band are the bands closest to the Fermi level and thus determine the electrical conductivity of the solid. In non-metals, the valence band is the highest range of electron energies in which electrons are normally present at absolute zero temperature, while the conduction band is the lowest range of vacant electronic states. On a graph of the electronic band structure of a material, the valence band is located below the Fermi level, while the conduction band is located above it. This distinction is meaningless in metals where conduction occurs in one or more partially filled bands, taking on the properties of both the valence and conduction bands.

In semiconductors and insulators the two bands are separated by a band gap, while in semimetals the bands overlap. A band gap is an energy range in a solid where no electron states can exist due to the quantization of energy. Electrical conductivity of non-metals is determined by the susceptibility of electrons to excitation from the valence band to the conduction band.

In solids, the ability of electrons to act as charge carriers depends on the availability of vacant electronic states. This allows the electrons to increase their energy (i.e., accelerate) when an electric field is applied. Similarly, holes (empty states) in the almost filled valence band also allow for conductivity.

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