Sn, C and Si, Ge are all group XIV elements. Yet, Sn is a conductor, C is an insulator while Si and Ge are semiconductors. Why?
Hint: The conductivity of a material is decided by its energy bandgap.
A conductor is a conductor if there is no energy gap between the conduction band and valence band in its energy band diagram. For insulator, the energy gap is large and for semiconductor the energy gap is moderate.
The energy gap for Sn is 0 eV, for C is 5.4 eV, for Si is 1.1 eV and for Ge is 0.7 eV. related to their atomic size. Therefore Sn is a conductor, C is an insulator and Ge and Si are semiconductors.
