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Silicon is element number 14 on the periodic table, with the element symbol Si. Here is a collection of facts about this interesting and useful element:
Silicon Fact Sheet
- Credit for discovering silicon is given to Swedish chemist Jöns Jakob Berzelius, who reacted potassium fluorosilicate with potassium to produce amorphous silicon, which he named silicium, a name first proposed by Sir Humphry Davy in 1808. The name derives from the Latin words silex or silicis, which mean "flint". It's probable English scientist Humphry Davy may have isolated impure silicon in 1808 and French chemists Joseph L. Gay-Lussac and Louis Jacques Thénard may have produced impure amorphous silicon in 1811. Berzelius is credited for the element's discovery because his sample was purified by repeatedly washing it, while earlier samples were impure.
- Scottish chemist Thomas Thomson named the element silicon in 1831, keeping part of the name Berzelius had given, but changing the ending of the name to -on because the element showed more similarities to boron and carbon than to the metals that had -ium names.
- Silicon is a metalloid, which means it has properties of both metals and nonmetals. Like other metalloids, silicon has different forms or allotropes. Amorphous silicon is usually seen as a gray powder, while crystalline silicon is a gray solid with a shiny, metallic appearance. Silicon conducts electricity better than nonmetals, yet not as well as metals. In other words, it's a semiconductor. Silicon has a high thermal conductivity and conducts heat well. Unlike metals, it's brittle, and not malleable or ductile. Like carbon, it usually has a valence of 4 (tetravalent), but unlike carbon, silicon can also form five or six bonds.
- Silicon is the second most abundant element on Earth by mass, making up over 27% of the crust. It's commonly encountered in silicate minerals, such as quartz and sand, but only rarely occurs as a free element. It's the 8th most abundant element in the universe, found at levels of about 650 parts per million. It's the principal element in a type of meteorite called aerolites.
- Silicon is needed for plant and animal life. Some aquatic organisms, such as diatoms, use the element to construct their skeletons. Humans need silicon for healthy skin, hair, nails, and bones, and to synthesize the proteins collagen and elastin. Dietary supplementation with silicon may increase bone density and reduce the risk of osteoporosis.
- Most silicon is used to produce the alloy ferrosilicon. It's used to produce steel. The element is purified to make semiconductors and other electronics. The compound silicon carbide is an important abrasive. Silicon dioxide is used to make glass. Because silicate minerals are common, silicon oxides form rocks and are used to make glass and ceramics.
- Like water (and unlike most chemicals), silicon has a higher density as a liquid than as a solid.
- Natural silicon consists of three stable isotopes: silicon-28, silicon-29, and silicon-30. Silicon-28 is the most abundant, accounting for 92.23% of the natural element. At least twenty radioisotopes are also known, with the most stable being silicon-32, which has a half-life of 170 years.
- Miners, stone cutters, and people who live in sandy regions may inhale large quantities of silicon compounds and develop a lung disease called silicosis. Exposure to silicon may occur by inhalation, ingestion, skin contact, and eye contact. The Occupational Safety and Health Administration (OSHA) sets the legal limit for workplace exposure to silicon to 15 mg/m3 total exposure and 5 mg/m3 respiratory exposure for an 8-hour workday.
- Silicon is available at extremely high purity. Molten salt electrolysis of silica (silicon dioxide) or other silicon compounds can be used to obtain the element at >99.9% purity for use in semiconductors. The Siemens process is another method used to produce high purity silicon. This is a form of chemical vapor deposition where gaseous trichlorosilane is blown across a pure silicon rod to grow polycrystalline silicon (polysilicon) with a purity of 99.9999%.
Silicon Atomic Data
Element Name: Silicon
Element Symbol: Si
Atomic Number: 14
Classification: metalloid (semimetal)
Appearance: Hard gray solid with a silver metallic luster.
Atomic Weight: 28.0855
Melting Point: 1414 oC, 1687 K
Boiling Point: 3265 oC, 3538 K
Electron Configuration: 1s2 2s2 2p6 3s2 3p2
Density: 2.33 g/cm3 (as a solid near room temperature); 2.57 g/cm3 (as a liquid at the melting point)
Oxidation States: 4, 3, 2, 1, -1, -2, -3, -4
Electronegativity: 1.90 on the Pauling scale
Atomic Radius: 111 pm
Crystal Structure: face-centered diamond cubic
Heat of Fusion: 50.21 kJ/mol
Heat of Vaporization: 383 kJ/mol
- Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.