Assertion: Among the carbon allotropes, diamond is an insulator, whereas, graphite is a good conductor of electricity. Reason: Hybridization of carbon in diamond and graphite are s p 3 and s p 2 respectively.

Step-by-step solution

Diamond has strong 3 - Dimensional network structure as every carbon is linked with   4 other carbons tetrahedrally via s p 3 hybridization. In graphite, every carbon is linked to 3   other carbon to forms sheet-like hexagonal structure, and the free electron is along with the layer so good conductor of electricity along with the layer.