Silicon
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| General | |||||||||||||||||||||||||||||||
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| Name, Symbol, Number | Silicon, Si, 14 | ||||||||||||||||||||||||||||||
| Series | metalloid | ||||||||||||||||||||||||||||||
| Group, Period, Block | 14 (IVA), 3, p | ||||||||||||||||||||||||||||||
| Density, Hardness | 2330 kg/m3, 6.5 | ||||||||||||||||||||||||||||||
| Appearance | dark grey, bluish tinge | ||||||||||||||||||||||||||||||
| Atomic Properties | |||||||||||||||||||||||||||||||
| Atomic weight | 28.0855 amu | ||||||||||||||||||||||||||||||
| Atomic radius (calc.) | 110 (111)pm | ||||||||||||||||||||||||||||||
| Covalent radius | 111 pm | ||||||||||||||||||||||||||||||
| van der Waals radius | 210 pm | ||||||||||||||||||||||||||||||
| Electron configuration | [Ne]3s2 3p2 | ||||||||||||||||||||||||||||||
| e- 's per energy level | 2, 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 | |||||||||||||||||||||||||||||||
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| 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:
- 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 some steels.
- 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, and 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 more conductive for use in transistors, solar cells and other semiconductor devices which are used in electronics and other high-tech applications.
- Silicon can be used in lasers to produce coherent light with a wavelength of 4560 angstroms.
- Silicones are flexible compounds containing silicon-oxygen and silicon-carbon bonds; they are widely used in applications such as artificial breast implants and contact lenses.
- Hydrogenated amorphous silicon has shown promise in the production of low-cost, large-area electronics and solar cells.
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.