Graphite is an example of:
(a) ionic solid
(b) covalent solid
(c) van der waals solid
(d) metallic solid

Hint: Graphite is an allotrope of carbon. It is a crystalline form of carbon. It is one of the most stable forms of carbon under standard conditions.

Complete Solution :
Graphite is a compound containing the element carbon with its atoms arranged in hexagonal structure. Under high pressure and temperature, it can be converted to diamond. The carbon in graphite has \[s{{p}^{2}}\] hybridisation. The atoms form in planes and each of them are bounded on three nearest neighbours 120 degrees apart. Graphite consists of layers, which are held together by weak van der-waals forces. There individual sheets are called graphene. In each layer the carbons are arranged in a honeycomb lattice, and have a separation of 0.142 nm, and the distance between the planes is 0.335 nm.
- Therefore, the bonds between the carbon atoms are covalent and are very strong. It is very difficult to break an individual sheet, but the sheets can be cleaved easily due to the presence of weak van der-waals force between them.
So, the correct answer is “Option B”.

We know that the carbon in graphite is \[s{{p}^{2}}\]. There is one free electron present, which can move along the individual sheet. This is what keeps the sheet strong. Each carbon contributes to one free electron. This allows graphite to conduct electricity. It has a wide range of applications due its property to conduct electricity.

Note: It can be mistaken that graphite is a van der-waal solid, due to the van der-waal forces present between the sheets of graphite. But this is not the case. The whole crystal lattice is due to the covalent bonds between the carbon atoms making it a covalent solid.