Silicon

Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. A tetravalent metalloid, silicon is less reactive than its chemical analog carbon. It is the eighth most common element in the universe by mass, but silicon very rarely occurs as the pure free element in nature. Silicon is more widely distributed in dusts, planetoids and planets as various forms of silicon dioxide (silica) or silicates. Silicon has many industrial uses. It is the principal component of most semiconductor devices, most importantly integrated circuits or microchips. Silicon is widely used in semiconductors because it remains a semiconductor at higher temperatures than the semiconductor germanium and because its native oxide is easily grown in a furnace and forms a better semiconductor/dielectric interface than any other material.

In the form of silica and silicates, silicon forms useful glasses, cements, and ceramics. It is also a constituent of silicones, a class-name for various synthetic plastic substances made of silicon, oxygen, carbon and hydrogen, often confused with silicon itself.

Silicon is an essential element in biology, although only tiny traces of it appear to be required by animals. It is much more important to the metabolism of plants and silicic acid (a type of silica) forms the basis of the striking array of protective shells of the microscopic diatoms.

Characteristics

The outer electron orbitals (half filled subshell holding up to eight electrons) have the same structure as in carbon and the two elements are sometimes similar chemically. Even though it is a relatively inert element, silicon still reacts with halogens and dilute alkalis, but most acids (except for some hyper-reactive combinations of nitric acid and hydrofluoric acid) do not affect it. Having four bonding electrons however gives it, like carbon, many opportunities to combine with other elements or compounds under the right circumstances. Both silicon and (in certain aspects) carbon are semiconductors, readily either donating or sharing their four outer electrons allowing many different forms of chemical bonding. Pure silicon has a negative temperature coefficient of resistance, since the number of free charge carriers increases with temperature. The electrical resistance of single crystal silicon significantly changes under the application of mechanical stress due to the piezoresistive effect. In its crystalline form, pure silicon has a grey color and a metallic luster. It is similar to glass in that it is rather strong, very brittle, and prone to chipping. Silicon is one of the few substances, like water and gallium, whose density is higher in liquid than in solid state, so it expands when it freezes.

Value

The base value of each unit of ranges between 1 and 15Ð per unit, with up to 2 units being found at any one time.

Presence on Mars: Rare