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Question
Explain why, diamond is hard while graphite is soft (though both are made of carbon atoms).
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Solution
Even if diamond and graphite are made up of carbon, the former is extremely hard while the latter is soft. Diamond is hard because of the strong covalent bond between its carbon atoms forming a regular tetrahedron which is hard to break. Graphite, on the other hand, consists of flat hexagonal ring forming layers of carbon atoms. The various layers of the carbon atoms are far apart from each other; hence, the covalent bond cannot exist. The layers are held together by weak van der Waals forces, thereby allowing them to slide over each other. Due to this layered structure, graphite is softer than diamond.
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