Diamond and graphite both are pure form of carbon but why graphite conduct electricity while diamond work as insulator?
Answers
Bcoz graphite have some free electron present in its structure whereas diamond have all its carbon atoms' valency satisfied and there is no free electron present.
Diamond and graphite are both allotropes of carbon; they are both made entirely of the same element (carbon) but they differ in the way that the atoms bond with each other and arrange themselves in a structure. Each carbon atom has 4 electrons in its outer shell that it can share with other atoms in order to form 4 covalent bonds. Diamond is a giant covalent structure; each valence electron (outer shell electron) of every carbon atom forms a covalent bond, which means that there are no free electrons. Since electrical conductivity relies on the flow of free electrons, diamond is not a good conductor.
Graphite on the other hand, although also only made up of carbon atoms, is the only non-metal that can conduct electricity. This is because only 3 of the available valence electrons form covalent bonds leaving 1 spare electron, which then becomes delocalised. This delocalised electron is no longer associated with one particular carbon atom and it is able to move freely between the carbon layers of graphite and conduct electricity.