Conduction of Electricity in Metals

A conductor may carry current either by the movement of electrons or by the movement of ions. Metallic conductors belong to the first category and electrolytes to the second.

Metals conduct in both the solid and molten states, and their conductivity depends on the number of valence electrons per atom. The atomic orbitals of the metal atoms combine to form molecular orbitals that are so close in energy that they merge into a band.

As Fig. 1.33 illustrates:

• If this band is only partially filled, or if a filled band overlaps a higher, empty conduction band, the electrons can move freely under an applied field and the solid conducts — this is a metal (Fig. 1.33a). …