2007 Schools Wikipedia Selection. Related subjects: Chemical elements

14 aluminiumsiliconphosphorus


Periodic Table - Extended Periodic Table
Name, Symbol, Number silicon, Si, 14
Chemical series metalloids
Group, Period, Block 14, 3, p
Appearance dark gray, bluish tinge
Atomic mass 28.0855 (3) g/mol
Electron configuration [Ne] 3s2 3p2
Electrons per shell 2, 8, 4
Physical properties
Phase solid
Density (near r.t.) 2.33 g·cm−3
Liquid density at m.p. 2.57 g·cm−3
Melting point 1687  K
(1414 ° C, 2577 ° F)
Boiling point 3538 K
(3265 ° C, 5909 ° F)
Heat of fusion 50.21 kJ·mol−1
Heat of vaporization 359 kJ·mol−1
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 1908 2102 2339 2636 3021 3537
Atomic properties
Crystal structure Diamond Lattice
Oxidation states 4
( amphoteric oxide)
Electronegativity 1.90 (Pauling scale)
Ionization energies
( more)
1st: 786.5 kJ·mol−1
2nd: 1577.1 kJ·mol−1
3rd: 3231.6 kJ·mol−1
Atomic radius 110 pm
Atomic radius (calc.) 111 pm
Covalent radius 111 pm
Van der Waals radius 210 pm
Magnetic ordering nonmagnetic
Young's modulus 47 GPa
Bulk modulus 100 GPa
Mohs hardness 6.5
CAS registry number 7440-21-3
Selected isotopes
Main article: Isotopes of silicon
iso NA half-life DM DE ( MeV) DP
28Si 92.23% Si is stable with 14 neutrons
29Si 4.67% Si is stable with 15 neutrons
30Si 3.1% Si is stable with 16 neutrons
32Si syn 132 y β- 13.020 32P
Not to be confused with Silicone.

Silicon ( IPA: /ˈsɪlikən/, Latin: silicium) is the 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 mass. It does not occur free in nature. It mainly occurs in minerals consisting of (practically) pure silicon dioxide in different crystalline forms (quartz, chalcedony, opal) and as silicates (various minerals containing silicon, oxygen and one or another metal), for example feldspar. These minerals occur in clay, sand and various types of rock like granite and sandstone. Silicon is the principal component of most semiconductor devices and, in the form of silica and silicates, in glass, cement, and ceramics. It is also a component of silicones, a name for various plastic substances often confused with silicon itself. Silicon is widely used in semiconductors because it remains a semiconductor at higher temperatures than the semiconductor Germanium and because its native oxide is easily grown in a furnace and forms a better semiconductor/dielectric interface than almost all other material combinations.

Notable characteristics

In its crystalline form, silicon has a dark gray colour and a metallic luster. It is similar to glass in that it is rather strong, very brittle, and prone to chipping. Even though it is a relatively inert element, silicon still reacts with halogens and dilute alkalis, but most acids (except for a combination of nitric acid and hydrofluoric acid) do not affect it. Elemental silicon transmits more than 95% of all wavelengths of infrared light. Pure silicon has a negative temperature coefficient of resistance, since the number of free charge carriers increases with temperature. The electrical resistance of single crystal silicon significantly changes under the application of mechanical stress due to the piezoresistive effect.


Silicon is a very useful element that is vital to many human industries. Silicon is used frequently in manufacturing computer chips and related hardware.

Silicon and alloys

  • The largest application of pure silicon (metallurgical grade silicon) is in aluminium - silicon alloys, often called "light alloys", to produce cast parts, mainly for automotive industry (this represents about 55% of the world consumption of pure silicon).
  • Pure silicon is also used to produce ultrapure silicon for electronic and photovoltaic applications :
    • Semiconductor - Ultrapure silicon can be doped with other elements to adjust its electrical response by controlling the number and charge ( positive or negative) of current carriers. Such control is necessary for transistors, solar cells, semiconductor detectors and other semiconductor devices which are used in electronics and other high-tech applications.
    • Photonics - Silicon can be used as a continuous wave raman laser to produce coherent light with a wavelength of 1,698 nm.
    • LCDs and solar cells - Hydrogenated amorphous silicon is widely used in the production of low-cost, large-area electronics in applications such as LCDs. It has also shown promise for large-area, low-cost solar cells.
  • Steel and cast iron - Silicon is an important constituent of some steels, and it is used in the production process of cast iron. It is introduced as ferro-silicon or silico-calcium alloys.

Silicon compounds

  • Pottery/ Enamel - It is a refractory material used in high-temperature material production and its silicates are used in making enamels and pottery.
  • Abrasives - Silicon carbide is one of the most important abrasives.


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 Thénard probably prepared impure amorphous silicon through the heating of potassium with silicon tetrafluoride. In 1824 Berzelius prepared amorphous silicon using approximately the same method as Lussac. Berzelius also purified the product by repeatedly washing it.

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.


Measured by mass, silicon makes up 25.7% of the Earth's crust and is the second most abundant element on Earth, after oxygen. Pure silicon crystals are rarely found in nature; natural silicon is usually found in the form of silicon dioxide (also known as silica) and silicate.

It is estimated to be the seventh most plentiful element in the universe.

Sand, amethyst, agate, quartz, rock crystal, flint, jasper, and opal are some of the forms in which silicon dioxide appears (they are known as " lithogenic", as opposed to " biogenic", silicas). Granite, asbestos, feldspar, clay, hornblende, and mica are a few of the many silicate minerals. Pure silicon crystals can be found as inclusions with gold and in volcanic exhalations.

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



SiO2 + C → Si + CO2


2 SiC + SiO2 → 3 Si + 2 CO




Physical methods

Silicon wafer with mirror finish (NASA)
Silicon wafer with mirror finish (NASA)


In zone melting, also called zone refining, the first silicon purification method to be widely used industrially, rods of metallurgical grade silicon are heated to melt at one end. Then, the heater is slowly moved down the length of the rod, keeping a small length of the rod molten as the silicon cools and resolidifies behind it. Since most impurities tend to remain in the molten region rather than resolidify, when the process is complete, most of the impurities in the rod will have been moved into the end that was the last to be melted. This end is then cut off and discarded, and the process repeated if a still higher purity was desired.

Chemical methods



2 HSiCl3 → Si + 2 HCl + SiCl4

Silicon produced from this and similar processes is called polycrystalline silicon. Polycrystalline silicon typically has impurity levels of less than 10-9.

At one time, DuPont produced ultrapure silicon by reacting silicon tetrachloride with high-purity zinc vapors at 950 °C, producing silicon according to the chemical equation

SiCl4 + 2 Zn → Si + 2 ZnCl2

However, this technique was plagued with practical problems (such as the zinc chloride byproduct solidifying and clogging lines) and was eventually abandoned in favour of the Siemens process.


The majority of silicon crystals grown for device production are produced by the Czochralski process, since it is the cheapest method available. However, silicon single-crystals grown by the Czochralski method contain impurities since the crucible which contains the melt dissolves. For certain electronic devices, particularly those required for high power applications, silicon grown by the Czochralski method is not pure enough. For these applications, float-zone silicon (FZ-Si) can be used instead.

Different forms of silicon

One can notice the colour change in silicon nanopowder. This is caused by the quantum effects which occur in particles of nanometric dimensions. See also Potential well, Quantum dot, and Nanoparticle


Silicon has numerous known isotopes, with mass numbers ranging from 22 to 44. 28Si (the most abundant isotope, at 92.23%), 29Si (4.67%), and 30Si (3.1%) are stable; 32Si is a radioactive isotope produced by argon decay. Its half-life, has been determined to be approximately 132 years, and it decays by beta emission to 32P (which has a 14.28 day half-life ) and then to 32S.


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.

Silicon-based life

Since silicon is similar to carbon, particularly in its valency, some people have proposed the possibility of silicon-based life. This concept is especially popular in science fiction. One main detraction for silicon-based life is that unlike carbon, silicon does not have the tendency to form double and triple bonds.





A. G. Cairns-Smith has proposed that the first living organisms to exist were forms of clay minerals - which were probably based around the silicon atom.



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