question_answer 37)

  Sn, C and Si, Ge are all group XIV elements. Yet, 5n is a conductor, C is an insulator while Si and Ge are semiconductors. Why?

Answer:

                  A material is a conductor if in its energy band diagram, there is no energy gap between conduction band and valence band. For insulator the energy gap is large and for semiconductor the energy gap is moderate. The energy gap for isis for Si is and for  is , related to their atomic size . Therefore,  is a conductor, C is an insulator and  and Si are semiconductors.