Dear Student
Graphite is considered as the good conductor of electricity. Its structure is the main reason for this property. Each carbon atom in graphite is directly linked to only three carbon atoms through covalent bonds. Therefore, of the four valence electrons in a carbon atom only three are used for bonding and the fourth is relatively free and can move from one carbon atom to the other. These free electrons make graphite a good conductor of electricity.
While in diamond, all the four electrons are involved in bonding with surrounding four carbon atoms. So no electron is free for conduction of electricity. This is the reason, diamond is a bad conductor of electricity.
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