Silicon: Difference between revisions

iso	NA	half-life	DM	DE M eV	DP
²⁸Si	92.23%	Si is stable with 10 neutrons
²⁹Si	4.67%	Si is stable with 11 neutrons
³⁰Si	3.1%	Si is stable with 12 neutrons
³²Si	{syn}	276 y	Beta^-	0.224	³²P

SI units & STP are used except where noted.

Silicon is a chemical element in the periodic table that has the symbol Si and atomic number 14. A tetravalent metalloid, silicon is less reactive than its chemical analog carbon. It is the second most abundant element in the Earth's crust, making up 25.7% of it by weight. It occurs in clay, feldspar, granite, quartz and sand, mainly in the form of silicon dioxide (also known as silica) and silicates (compounds containing silicon, oxygen and metals). Silicon is the principal component of glass, semiconductors, cement, ceramics and silicones, the latter a plastic substance often confused with silicon.

Notable Characteristics

Silicon when in its crystalline form has a metallic luster and a grayish color. Even though it is a relatively inert element, silicon is still attacked by halogens and dilute alkalis but most acids, except for hydrofluoric acid do not affect it. Elemental silicon transmits more than 95% of all wavelengths of infrared light.

Applications

Silicon is a very useful element that is vital to many human industries. Silicon dioxide in the form of sand and clay is an important ingredient of concrete and brick and is also used to produce Portland cement. Silicon is a very important element for plant and animal life. Diatoms extract silica from water to build their protective cell walls. Other uses:

It is a refractory material used in high-temperature material production and its silicates are used in making enamels and pottery.
Silicon is an important constituent of steel.
Silica from sand is a principal component of glass. Glass can be made into a great variety of shapes and is used to make window glass, containers, insulators, among many other uses.
Silicon carbide is one of the most important abrasives.
Ultrapure silicon can be doped with arsenic, boron, gallium, or phosphorus to make silicon for use in transistors, solar cells and other solid-state devices which are used in electronics and space-age industries.
Used in lasers to produce coherent light of 4560 angstroms.
Silicones are flexible compounds containing silicon-oxygen and silicon-carbon bonds; they are widely used in industry.

Hydrogenated amorphous silicon has shown promise in the production of economical solar cells for converting solar energy into electricity.

History

Silicon (Latin silex, silicis meaning flint) was first identified by Antoine Lavoisier in 1787, was later mistaken by Humphry Davy in 1800 for a compound. In 1811 Gay Lussac and Thenard probably prepared impure amorphous silicon through the heating of potassium with silicon tetrafluoride. In 1824 Berzelius prepared amorphous silicon using approximately the same method of Lussac. Berzelius also purified the product by repeatedly washing it.

Occurrence

Silicon is a principal component of aerolites which are a class of meteoroids and also of tektites which is a natural form of glass.

Measured by weight, silicon makes up 25.7% of the earth's crust and after oxygen is also the second most abundant element. Silicon is not found unbound in nature occurring most often as oxides and as silicates. Sand, amethyst, agate, quartz, rock crystal, flint, jasper, and opal are some of the forms in which the oxide appears. Granite, asbestos, feldspar, clay, hornblende, and mica are a few of the many silicate minerals.

Silicon is commercially prepared by the heating of silica and carbon in an electric furnace by using carbon electrodes. The Czochralski process is often used to make single silicon crystals that are used in solid-state/semiconductor devices.

In 1997 regular grade silicon (99% purity) cost about $ 0.50 per g.

Isotopes

Silicon has nine isotopes, with mass numbers from 25-33. Si-28 (the most abundant isotope, at 92.23%), Si-29 (4.67%), and Si-30 (3.1%) are stable; Si-32 is a radioactive isotope produced by argon decay. Its half-life, after much argument, has been determined to be approximately 276 years, and it decays by beta emission to P-32 (which has a 14.28 year half-life) and then to S-32.

Precautions

A serious lung disease known as silicosis often occurred in miners, stonecutters, and others who were engaged in work where siliceous dust was inhaled in great quantities.

@@ Line 125: / Line 125: @@
 Silicon is commercially prepared by the heating of silica and [[carbon]] in an electric furnace by using carbon [[electrode]]s. The [[Czochralski process]] is often used to make single silicon crystals that are used in [[solid-state]]/[[semiconductor]] devices.
-In 1997 regular grade silicon (99% purity) cost about [[United States dollar|$]] 0.50 per [[gram|g]].
+In 1997 regular grade silicon (99% purity) cost about [[United States dollar|$]] 0.50 per [[gram (unit)|g]].
 == Isotopes ==
 Silicon has nine [[isotope]]s, with [[mass number]]s from 25-33. Si-28 (the most abundant isotope, at 92.23%), Si-29 (4.67%), and Si-30 (3.1%) are stable; Si-32 is a [[radioactive]] isotope produced by [[argon]] decay. Its [[half-life]], after much argument, has been determined to be approximately 276 years, and it decays by [[beta emission]] to [[phosphorus|P]]-32 (which has a 14.28 year half-life) and then to [[sulfur|S]]-32.

Revision as of 11:20, 13 November 2002