Question

Sn,C,Si and Ge are all group 14 elements .Yet ,Sn is a conducter ,C is an insulter while Si and Ge are semiconducter.why?

Answer 1

As Sn is large in size so it is ready to loose it's electron to attain stability as it's electrons are loosely bounded by innermost shell. Hence conduct electricity.
In carbon electrons are closely bounded. So not free to conduct electricity. Hence are insulator.
Si and Ge are also insulator but on providing external parameters they conduct electricity. Hence are semiconductor.