Molecular orbital bands
The central idea underlying the description of the electronic structure of solids is that the valence electrons supplied by the atoms spread through the entire structure. This concept is expressed more formally by making a simple extension of M0 theory in which the solid is l treated like an indefinitely large molecule 16 The description in terms of delocalized electrons can also be used to describe nonmetallic solids. We shall therefore begin by showing how metals are described in terms of molecular orbitals. Then we shall go on to show that the same principles can be applied, but with a different outcome, to ionic and molecular solids.