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Allotropes of carbon: Identify the hardest and the softest allotrope among the given pairs. Use known mechanical properties of carbon forms (sp³ vs sp²/amorphous). Choose the correct pair.

Difficulty: Easy

Coke is the hardest; graphite is the softest
Diamond is the hardest; coke is the softest
Diamond is the hardest; graphite is the softest
Diamond is the hardest; lamp black is the softest

Correct Answer: Diamond is the hardest; graphite is the softest

Explanation:

Given data

Compare carbon allotropes for hardness.

Concept/Approach
Diamond (3D sp³ network) has extremely strong covalent bonds → highest hardness. Graphite has layered sp² sheets with weak interlayer forces → very soft and lubricating.

Final Answer
Diamond is the hardest; graphite is the softest

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