Silicon is one of the most useful elements to mankind. Silicon makes up 27.7% of the Earth’s crust by mass and is the second most abundant element (oxygen is the first). It does not occur uncombined in nature but mainly as oxide (silica) and as silicates. The oxide includes sand, quartz, rock crystal, amethyst, agate, flint and opal. The silicate form includes asbestos, granite, hornblende, feldspar, clay and mica. It is combined to make alloys such as aluminium-silicon and ferro-silicon (iron-silicon).
Silicon is one of seven elements that are known as the metalloids. They don’t behave exactly like metals or exactly like non-metals. Silicon can have properties like a metal or a non-metal depending on what other elements it is combined with. Glass is a very common silicon compound that has non-metal qualities, while the silicon used in electronics acts very much like a metal. Silicon is a semiconductor, meaning that it does conduct electricity. Unlike a typical metal, however, silicon gets better at conducting electricity as the temperature increases. Normally a metal gets worse at conductivity the higher the temperature.
Silicon Valley gets its name from this material, as it is in high-tech that it has really made a mark. As a semiconductor, silicon is used to make transistors, which amplify or switch electrical currents for electronics from radios to iPhones. Silicon carbides are important abrasives and are also used in lasers. Silicon is also used in various ways in solar cells and computer chips, as well as dynamo and transformer plates, engine blocks, cylinder heads, machine tools and to deoxidise steel. Silicon is also used to make silicones. These are silicon-oxygen polymers with methyl groups attached. Silicone oil is a lubricant and is added to some cosmetics and hair conditioners. Silicone rubber is used as a waterproof sealant in bathrooms and around windows, pipes and roofs. Silicon is non-toxic but some silicates, such as asbestos, are carcinogenic.