Structure of Diamond:
The important properties of diamond is related to its structure. In Diamond, each carbon atom is in an sp3 hybridised state and is linked to four other neighbouring carbon atoms held at the corners of a regular tetrahedron by covalent bonds. This results in a very big three-dimensional polymeric cage-like structure in which the C-C bond distance is 1.54Å and bond angles 109°28′.
Owing to very strong covalent bonds by which the atoms are held together. Diamond is the hardest substance known, possesses abnormally high m/p (3600°C) and it is extremely inert chemically. Further, since all the electrons are used in bond formation. There is no mobile electron and hence diamond crystals are a non-conductor of electricity.
Uses:
i. Precious stones for jewellery
ii. Cutting Glass
iii. Rock boring purposes
iv. As an abrasive
Structure of Graphite:
In Graphite, each carbon atom is in sp2 hybridized state and it is linked to three other neighbouring carbon atoms by three sigma bonds forming a Hexa-decimal planar structure. The 4th electron present forms a π-bond. The π-electron being mobile, graphite conducts electricity. Also due to the presence of mobile electrons graphite is more reactive than diamond.
Graphite forms are two-dimensional sheet-like polymeric structures. The adjacent layers are held together by weak Vander Waal’s forces and the distance between the two layers is sufficiently large (3.4Å). Due to wide separation and weak interlayer bonds, the two adjacent layers can easily slide over each other which gives its lubricating property, low density, and soft and greasy nature. Carbon atoms within a layer are held together by strong covalent bonds. hence graphite has strong covalent bonds. Hence, graphite has a high m.p (3500°C) like a diamond.
Uses:
i. Lubricant
ii. In-making electrodes and carbon arcs
iii. Lead pencils