Hence, the total number of outer electrons
in the crystal is 4N The maximum possible number of electrons in the
outer orbit is 8 (2s + 6p electrons) So, for the 4N valence electrons there
are 8N available energy states These 8N discrete energy levels can either
form a continuous band or they may be grouped in different bands
depending upon the distance between the atoms in the crystal (see box
on Band Theory of Solids)