Solids exhibit an amazing range of electrical conductivities, extending over 27 orders of magnitude ranging from 10^–20 to 10⁷ ohm^–1 m^–1.

Solids can be classified into three types on the basis of their conductivities.

(i) Conductors: The solids with conductivities ranging between 10⁴ to 10⁷ ohm^–1m^–1 are called conductors. Metals have conductivities in the order of 10⁷ ohm^–1m^–1 are good conductors.

(ii) Insulators: These are the solids with very low conductivities ranging between 10^–20 to 10^–10 ohm^–1m^–1.

(iii) Semiconductors: These are the solids with conductivities in the intermediate range from 10^–6 to 10⁴ ohm^–1m^–1.

The conductivity of metals in solid state depends on which of the following factors?

Number of valence electrons available per atom

Conduction of Electricity in Metals

Metals conduct electricity in solid as well as molten state. The conductivity of metals depends upon the number of valence electrons available per atom. The atomic orbitals of metal atoms form molecular orbitals which are so close in energy to each other as to form a band. If this band is partially filled or it overlaps with a higher energy unoccupied conduction band, then electrons can flow easily under an applied electric field and the metal shows conductivity.