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?
For insulator the energy gap is large and for semiconductor the energy gap is moderate. The energy gap for Sn is 0eV, for C is `5.4 eV`, for Si is `1.1eV` 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.
