Question
Mon December 12, 2011 By: Abinash Tarai

Why is diamond hard and graphite soft if both are made of carbon?

Expert Reply
Mon December 12, 2011

Diamond has three dimensional network of strong covalent bonds.  It is very difficult to break extended covalent bonding and therefore, diamond is the hardest substance on earth. On the other hand, graphite has layer structure and the layers are held together by weak Vander WaalsÂ’ forces. Therefore, graphite cleaves easily between the layers and, therefore, it is very soft and slippery.

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