Question

Graphite is good conductor of current but diamond is non-conductor because:

• A. diamond is hard and graphite is soft
• B. graphite and diamond have different atomic configuration
• C. graphite is composed of positively charged carbon ions
• D. graphite has hexagonal layer structure with mobile $\pi$-electrons while diamond has continuous tetrahedra covalent structure with no free electrons

Answer 1

The correct option is D graphite has hexagonal layer structure with mobile $\pi$-electrons while diamond has continuous tetrahedra covalent structure with no free electrons

Diamond has 3D carbon network so the structure is rigid with carbon bonded to four other carbon in space.
This is the reason that diamond is hardest substance known. Since all the four carbon atoms are involved in bonding and there is no free electron in the crystal structure of diamond. Therefore diamond is non-conductor of electricity.
Graphite has two dimensional sheet like structure. Each carbon atom is covalently bonded to three other carbon atom and fourth electron is forms a $\pi$ bond. The various layers are held together by weak van der Waals forces of atoms. This is the reason graphite has soft and slippery structure. The electrons are delocalised over the whole sheet and they are mobile. Therefore diamond is a good conductor of electricity.