Question

The hardest form of carbon is:

• A. Coke
• B. Graphite
• C. Diamond
• D. Charcoal

Hint:

Compare the bonding structures of the different allotropes of carbon.

Answer 1

The Correct Option is C

Step 1: Carbon exists in several allotropic forms, including diamond, graphite, coke and charcoal.

Step 2: In diamond, every carbon atom is joined to four other carbon atoms by strong covalent bonds arranged in a rigid three dimensional tetrahedral network, since carbon is sp3 hybridised in this structure.

Step 3: This continuous, strongly bonded three dimensional lattice makes diamond extremely rigid and gives it the highest hardness of any known natural substance, which is why it is used in cutting tools and drilling equipment.

Step 4: Graphite, coke and charcoal are all forms of carbon with layered or amorphous structures held together by weaker forces. Graphite has weak forces between its layers, while coke and charcoal are impure amorphous carbon, so all three are far softer than diamond.

Step 5: Hence the hardest allotrope of carbon is diamond, option C.