Atomic Number: 14
Atomic Symbol: Si
Atomic Weight: 28.0855
Melting Point: 2,577 F (1,414 C) |
Boiling Point: 5,909 F (3,265 C)
Word origin: The word silicon comes from the Latin word silex, silicis (flint).
Discovery:Jöns Jacob Berzelius is generally credited with the discovery of silicon. In 1824, he was the first to prepare a pure form of amorphous silicon through heating potassium with silicon tetraflouride then repeatedly washing the product to remove the fluosilicates. Impure amorphous silicon had already been discovered in 1811, however, by Gay Lussac and Louis Jacques Thénard. In 1854, Henri Etienne Sainte-Claire Deville first prepared crystalline silicon, the second allotropic form of the element.
Properties of silicon
Silicon is a relatively inert element, and most acids do not affect it. Hydrofluoric acid is the exception. Silicon is also attacked by halogens and dilute alkali. [See Periodic Table of the Elements]
Crystalline silicon has a metallic luster and a grayish color. Elemental silicon transmits more than 95 percent of all wavelengths of infrared light, from 1.3 to 6.y micro-m.
Those who breathe large quantities of develop a serious lung disease known as silicosis. Miners and stonecutters are typically at high risk.
Sources of silicon
Silicon is the second most abundant element in the world, exceeded only by oxygen. It makes up 25.7 percent of Earth’s crust by weight, and is found in the sun and stars. It is a principal component of a class of meteorites called aerolites. It is also a component of tektites, a natural glass of uncertain origin.
Silicon is not found free in nature, but it does occur as oxide and silicates in some minerals. The oxide appears in sand, quartz, rock crystal, amethyst, agate, flint, jasper and opal, among others. A few of the many silicate minerals are granite, hornblende, asbestos, feldspar, clay and mica.
Silicon can be prepared commercially by heating silica and carbon in an electric furnace, using carbon electrodes. The element can be prepared in many other ways, too. Amorphous silicon can be prepared as a brown, easily melted-or-vaporized powder. Single crystals of silicon can be produced and used for solid-state or semiconductor devices. Hyper-pure silicon can be prepared through thermal decomposition of ultra-pure trichlorosilane in a hydrogen atmosphere, and by a vacuum float zone process.
Uses of silicon
Humans make great use of silicon. In the forms of sand and clay, it used to make concrete in brick; in its silicate form it can be used in making enamels, pottery, and more; and as a refractory material it can be used in high-temperature work. It is a fundamental component of steel. Silicon carbide is an important abrasive and has been used in lasers to produce coherent light of 4560A.
Silica, as sand, is the principal ingredient of glass, one of the world’s most inexpensive materials with excellent mechanical, optical, thermal and electrical properties. Silicon tetrachloride can be used to iridize glass.
Hyper-pure silicon can be combined with boron, gallium, phosphorus, and arsenic to produce silicon used in transistors, solar cells, rectifiers, and other devices used extensively in the electronics and space industries.
Hydrated amorphous silicon has shown promise of producing economical cells for converting solar energy into electricity.
Silicones are products of silicon, made by hydrolyzing a silicon organic chloride. This process can be used to produce a large number of polymeric products, or silicones, that range from liquids to hard, glasslike solids with many uses.
Humans aren’t the only ones who use silicon; the element is important to plant and animal life. Both fresh and salt water diatoms extract silica from water to build cell walls. Silica is present in the ashes of plants and in the human skeleton.
(Source: Los Alamos National Laboratory)