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:
In case of C the valence band is not completely filled at absolute zero temperature.
In case of C the conduction band is partly filled even at absolute zero temperature.
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.
The four bonding electrons in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit.
The four bonding electrons in the case of C lie in the second orbit whereas in case of si they lies in the third orbit. So loosely bound valence electrons are present in si as compared to c.
Option 1)
In case of C the valence band is not completely filled at absolute zero temperature.
This solution is incorrect
Option 2)
In case of C the conduction band is partly filled even at absolute zero temperature.
This solution is incorrect
Option 3)
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.
This solution is correct
Option 4)
The four bonding electrons in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit.
This solution is incorrect