Silicon

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.

Properties

General

Name, Symbol, Number

Silicon, Si, 14

Series

metalloid

Group, Period, Block

14 (IV), 3, p

Density, Hardness

2330 kg/m³, 6.5

Appearance

dark grey, bluish tinge

Atomic

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

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

Velocity 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)

1^st ionization potential

786.5 kJ/mol

2^nd ionization potential

1577.1 kJ/mol

3^rd ionization potential

3231.6 kJ/mol

4^th ionization potential

4355.5 kJ/mol

5^th ionization potential

16091 kJ/mol

6^th ionization potential

19805 kJ/mol

7^th ionization potential

23780 kJ/mol

8^th ionization potential

29287 kJ/mol

9^th ionization potential

33878 kJ/mol

10^th ionization potential

38726 kJ/mol

Most Stable Isotopes

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.

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.

Uses

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 Jons Jakob Berzelius prepared amorphous silicon using approximately the same method of Lussac. Berzelius also purified the product by repeatedly washing it.

Sources

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.

Information sources and external links:

WebElements.com - Silicon
EnvironmentalChemistry.com - Silicon