With respect to graphite and diamond, which of the statements given below are correct?
(i) Graphite is harder than diamond.
(ii) Graphite has higher electrical conductivity than diamond.
(iii) Graphite has higher thermal conductivity than diamond.
Graphite has higher `C-C` bond order than diamond.

Options

A. (i), (ii), (iii), (iv)
B. (ii), (ii)
C. (ii), (iv)
D. (ii), (iii), (iv)

Answer

C

Explanation

In graphite, the `pi` electrons are delocalized over the whole sheet, and as they are mobile, graphite conducts electricity. Due to the absence of mobile electrons (in diamond all the valency `e^(-)`s are firmly held in `sigma` bonds), diamond is an electrical insulator. However, diamond is an excellent thermal conductor, being about five times better than copper. The thermal conductivity is the direct consequece of diamond structure. because the giant molecule is held together by a continuous network of covalent bonds, little movement of individual `C` atoms can occur. Hence, any added heat energy will be transferred as molecular motion directly across the whole diamond.