Q. C and Si both have same lattice structure, having 4 bonding electrons in each. However, C is insulator where as Si is intrinsic semiconductor. This is because
A) The four bonding electrons in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit
B) In case of C the valance band is not completely filled at absolute zero temperature
C) In case of C the conduction band is partly filled even at absolute zero temperature
D) The four bonding electrons in the case of C lie in the second orbit, whereas in the case of Si they lie in the third
Explanation
[Solution from source] Carbon's four bonding electrons are in the second shell (n = 2) and silicon's in the third (n = 3). The more tightly bound carbon electrons give a much larger band gap (about 5.5 eV vs 1.1 eV), so diamond is an insulator. A partly filled band at absolute zero would make carbon a conductor, not an insulator. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.