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# Silicon

 Aluminum - Silicon - Phosphorus CSiGe Full table
General
Name, Symbol, NumberSilicon, Si, 14
Series metalloid
Group, Period, Block14 (IVA)[?], 3, p
Density, Hardness 2330 kg/m3, 6.5
Appearance dark grey, bluish tinge
Atomic Properties
Atomic weight 28.0855 amu
van der Waals radius 210 pm
Electron configuration [Ne]3s2 3p2
e- 's per energy level2, 8, 4
Oxidation states (Oxide) 4 (amphoteric)
Crystal structure Cubic face centered
Physical Properties
State of matter solid (nonmagnetic)
Melting point 1687 K (2577 °F)
Boiling point 3173 K (5252 °F)
Molar volume 12.06 ×10-3 m3/mol
Heat of vaporization 384.22 kJ/mol
Heat of fusion 50.55 kJ/mol
Vapor pressure 4.77 Pa at 1683 K
Speed of sound __ m/s at __ K
Miscellaneous
Electronegativity 1.90 (Pauling scale)
Specific heat capacity 700 J/(kg*K)
Electrical conductivity 2.52 10-4/m ohm
Thermal conductivity 148 W/(m*K)
1st ionization potential 786.5 kJ/mol
2nd ionization potential 1577.1 kJ/mol
3rd ionization potential 3231.6 kJ/mol
4th ionization potential 4355.5 kJ/mol
5th ionization potential 16091 kJ/mol
6th ionization potential 19805 kJ/mol
7th ionization potential 23780 kJ/mol
8th ionization potential 29287 kJ/mol
9th ionization potential 33878 kJ/mol
10th ionization potential 38726 kJ/mol
Most Stable Isotopes
isoNAhalf-life DMDE MeVDP
28Si92.23%Si is stable with 14 neutrons
29Si4.67%Si is stable with 15 neutrons
30Si3.1%Si is stable with 16 neutrons
32Si{syn}276 yBeta-0.22432P
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 In its crystalline form, silicon has a metallic luster and a grayish color. Even though it is a relatively inert element, silicon still reacts with 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:

History Silicon (Latin silex, silicis meaning flint) was first identified by Antoine Lavoisier in 1787, and 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. Elemental silicon is not found in nature. It occurrs 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 high-purity single silicon crystals for use 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.

Miscellaneous Information Because Silicon is an important element in semiconductor and high-tech devices, the high-tech region of Silicon Valley, California, is named after this element.

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