12. SILICON

12. SILICON

Silicon is the most abundant element found in the Earth’s crust. It is a bluish-grey metalloid which has a metallic lustre and is very brittle. It crystallizes in the diamond lattice, has a specific gravity of 2.42 (two point four two), melts at 1,420 ®C (degrees Centigrade) and boils at 3,500 ®C. It has an atomic weight of 28. The element is usually tetravalent in its compounds. It forms a great variety of inorganic and organic compounds.

Elementary silicon is used as an alloying constituent to strengthen aluminium, magnesium, copper and other metals. It also has a deoxidizing effect on steel, and in much larger propositions it also confers chemical inertness on ferrous alloys. High-purity silicon is used as the starting material for silicone resins, oils and in semiconductor devices, such as rectifiers, transistors and solar batteries.

Silicon dioxide, besides its use in tremendous quantities in the ceramic industries, is used as the raw material for making elementary silicon and for silicon carbide. Crystals of silicon carbide are used for piezoelectric devices. Fuzed quartz sand becomes silica glass, which is used in chemical laboratories and plants as well as an electric insulator.

Silicon forms useful and important compounds with hydrogen, carbon, the halogen elements, nitrogen, oxygen, and sulphur. In addition, useful organosilicon derivatives have been prepared.