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Question
Compare the structure of the crystal of diamond & graphite with special reference to the reason for diamond being the hardest natural substance while graphite one of the softest. Compare the electrical & thermal conductivity of the two crystalline allotropes of carbon.
Solution
- Structure of crystal of diamond : Hardest natural substance is due to – strength and uniformity of the carbon – carbon covalent bond [tetrahadron structure].
It is bad conductor of electricity and heat due to abscence of free electrons in the crystal, i.e. no electron is free to move. - Structure of graphite : “Is soft and greasy due to parallel layers of C-atoms held together by weak VANDER WAAL – forces which slide over one another, i.e. hexagonal structure.
It is good conductor of heat and electricity due to – presence of mobile electrons in the crystal.
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