Silicon
Silicon is a non-metal element denoted by the atomic symbol, Si. It has an atomic number of 14 and the average atomic weight of its isotopes is 28.0855. Making up twenty-seven percent of the earth's crust, silicon is our second most abundant element; oxygen is first at forty-seven percent and aluminum is third at thirteen percent. Although silicon forms compounds with sixty-four other stable and many unstable elements, oxygen is its most frequent partner. It is believed that the thousands of compounds which include both elements make up nearly ninety-seven percent of earth's crust.
Silicon's great abundance is reflected in its many thousands of uses, before and throughout recorded history. It is the primary element in flint, glass and microchips, making it an essential part of much technology from the stone age through the space age. Indeed, the name "silicon" was derived from silex, the Latin word for flint. Silicon never occurs naturally by itself. Some scientists even doubted its existence as a separate element until Swedish chemist Jöns Berzelius purified and confirmed it as the fiftieth known element in 1824. Crystalline silicon was not produced until 1854.
Most common natural occurrences of silicon are silicas (SO2 in forms such as quartz, flint, opal, sand and clay) and silicate minerals (SO4 units tied to metals such as aluminum, sodium, and potassium, to form mica, feldspar, garnet, tourmaline, emerald, aquamarine, asbestos, talc, zircon, and hundreds of other materials). There are also many natural organic ( carbon-based) silicon compounds.
Silicon compounds have many important uses. They are extremely slick so they have found uses as lubricants for industrial applications and consumer products. Silicon dioxide is one of the primary components of glass. It is also used as an abrasive. Other silicon compounds such as silicon carbide are used in the production of shoe soles, refractory bricks and furnace linings.
Silicon's semiconductor qualities, as demonstrated in transistors, made it the basis of modern computers and most other solid state electronic devices. The silicon atom contains fourteen protons and an average of fourteen neutrons in the nucleus, surrounded by fourteen electrons. Under normal conditions it is a relatively inert material which is an insulator, rather than a conductor, of electricity. However, a property of silicon's outer electron orbits (called "shells") permits silicon to be easily and repeatedly converted from an electrical insulator to a conductor and back again. This is achieved by adding energy (such as heat) to the silicon atom, which frees its outermost electrons, making them available to conduct current while at that energy level. The result is an electrical switch no larger than a molecule. Since binary computers are essentially collections of millions of on-off switches, the sub-microscopic size switches created with silicon semiconductors have permitted production of ever smaller, faster, less expensive and more reliable computers. This became possible starting in the late 1960s after scientists solved the problem of how to wire together millions of molecular switches and developed mass-production procedures for the resulting silicon semiconductor components, including integrated circuits and computer microprocessors.
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