Diamond

Diamond, a crystalline form of pure carbon, is an example of a covalent network substance. It widely used in jewellery because when cut and polished it sparkles brilliantly. Experimental evidence indicates that in diamond all the C-C bonds are of the same length and all the bond angles 109.50. using this information a diamond crystal can be pictured as a single giant molecule made up of a regular network of carbon atoms extending throughout the crystal. Each carbon atom can be imagined to be at the centre of a regular tetrahedron, surrounded by four other carbon atoms atatoms at the tetrahedron, surrounded by four other carbon atoms at the corners of the tetrahedron.

In this three dimensional network of atoms, each carbon atom forms four covalent bonds by sharing electrons with each of its four nearest neighbours. The bonding electrons are tightly bound and highly localized. Thus diamond crystals are non-conductors of electricity. It is also very difficult to distort diamond, and other covalent network crystals, since this would involve breaking many covalent bonds. Consequently, diamond is extremely hard and has a very high melting and boiling point. If the highly directional bonds in diamond are subjected to extreme stress, the crystal is unable to deform in shape and it shatters. Diamond is the hardest known naturally occurring substance. Diamond unsuitable for gemstone are used in applications such as glass cutting and polishing, mineral exploration drills, dentist’ drills and record player needles.