Discovered | Name | Characteristics | Found | Prepared | Reactions | Uses

Silicon, a metalloid, is in the 3rd period of Group IVA. Other members of the group are carbon (C), germanium (Ge), tin (Sn), and lead (Pb).

Impure amorphous silicon was probably prepared in 1811 by Gay-Lussac and Thénard by heating potassium with silicon tetrafluoride. Berzelius, generally credited with the discovery, finally succeeded in preparing amorphous silicon in 1824 by the same general method as used earlier, but he purified the product by removing the fluorosilicates by repeated washings. Crystalline silicon, the second allotropic form of the element was first prepared by Sainte-Claire Deville in 1854.

The name is derived from the Latin, silex and silicis, referring to flint. The symbol Si is an abbreviation of the name.

The element has a solid-state structure similar to carbon (diamond).

Silicon is present in the sun and stars and is a principal component of a class of meteorites known as aerolites. It is also a component of tektites, a natural glass of uncertain origin, but believed by many to be meteoritic. Silicon makes up 25.7% of the earth's crust, by weight, and is the second most abundant element, being exceeded only by oxygen.

Silicon is not found free in nature, but occurs chiefly as the oxide, and as silicates. Sand, quartz, rock crystal, amethyst, agate, flint, jasper, and opal are some of the forms in which the oxide appears. Hornblende, asbestos, feldspar, clay, and mica are but a few of the numerous silicate minerals.

Silicon is prepared commercially by heating silica and carbon in an electric furnace, using carbon electrodes. Amorphous silicon is a brown powder, which can be easily melted or vaporized. Crystalline silicon has a metallic luster and grayish color. Hyper-pure silicon can be prepared by the thermal decomposition of ultra-pure trichlorosilane in a hydrogen atmosphere, and by a vacuum float zone process. This product can be doped with boron, gallium, phosphorus, or arsenic, to produce silicon for use in transistors, solar cells, rectifiers, and other solid-state devices which are used extensively in the electronics industry.

Silicon is a relatively inert element, but it is attacked by halogens and dilute alkali. Most acids, except hydrofluoric, do not affect it.

Silicones are important products of silicon. They may be prepared by hydrolyzing a silicon organic chloride, such as dimethyl silicon dichloride. Hydrolysis and condensation of various substituted chlorosilanes can be used to produce a very great number of polymeric products, or silicones, ranging from liquids to hard, glass-like solids with many useful properties.

Silicon is one of the most useful elements. In the form of sand and clay it is used to make concrete and brick. It is a useful refractory material for high temperature work, and in the form of silicates it is used in making enamels and pottery.

Silica, as sand, is a principal ingredient of glass, one of the most inexpensive materials with excellent mechanical, optical, thermal, and electrical properties. Glass can be made in a very great variety of shapes, and is used as containers, window glass, insulators, and thousands of other uses.

Silicon is important in plant and animal life. Diatoms in both fresh and salt water extract silica from the water to build up their cell walls. Silica is present in ashes of plants and in the human skeleton. Silicon is an important ingredient in steel, and silicon carbide is one of the most important abrasives.