Chemistry
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.
Carbon
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Answer
| Property | Diamond | Graphite |
|---|---|---|
| Structure | A three dimensional octrahedral eight sided crystal. | A two dimensional sheetlike flat layered crystal. |
| Nature | Diamond is hardest natural substance. Hardness is due to the strength and uniformity of the carbon-carbon covalent bonds in stable and rigid crystal lattice. | Graphite is a soft substance. Softness is due to parallel layers of C atoms held together by weak Van Der Waals forces which slide over one another. |
| Electrical conductivity | Non-conductor of electricity due to absence of free electrons in the crystal. | Good conductor of electricity due to presence of mobile electrons in the crystal. |
| Thermal conductivity | Very poor conductor of heat | Good conductor of heat |
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Related Questions
Define the term 'allotropy'. Give a reason why carbon exhibits allotropy.
Name two crystalline and four amorphous allotropes of carbon.
With reference to the structure of the two crystalline allotropes of carbon, state why diamond is inert or unreactive while graphite is comparably more reactive.
State the reasons for
(a) Use of diamond - as an item of jewellery.
(b) Use of graphite -
(i) as a lubricant for heated machine parts,
(ii) as a lining for crucibles used in manufacture of high grade steel
(iii) as an electrode in electroplating.