Which is the purest form of carbon?

a) Charcoal

b) Coke

c) Diamond

d) Graphite

The correct answer is (c) Diamond

Diamond is considered the purest form of carbon in school chemistry. It is a crystalline allotrope in which each carbon atom is covalently bonded to four other carbon atoms in a tetrahedral (sp³) 3-D network. This perfectly ordered structure gives diamond its hallmark properties—extreme hardness, high thermal conductivity, transparency, and electrical insulation—and indicates that it is composed of only carbon.

Why are the others not the “purest”

(a) Charcoal: An amorphous form of carbon obtained by heating wood/bone in limited air. It usually contains ash, moisture, and other impurities.

(b) Coke: Produced by destructive distillation of coal; it is porous carbon but still has sulphur, ash, and mineral impurities. It is used mainly as a fuel and reducing agent in metallurgy.

(d) Graphite: A crystalline allotrope of carbon (layers of hexagonal rings) and chemically pure carbon too, but in textbook MCQs the “purest form” is conventionally diamond. Graphite is soft and conducts electricity (due to mobile electrons between layers) and commonly contains traces of other materials in practical use (e.g., pencil “lead” mixed with clay).