Silicon

"Si" redirects here. For other uses, see Si (disambiguation).

Silicon is a chemical element. Its atomic number is 14 on the periodic table. Its symbol is Si. It is a hard, brittle crystalline solid. It is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic table.

Silicon, ₁₄Si

Silicon
Pronunciation	/ˈsɪlɪkən/ (SIL-ik-ən) /ˈsɪləkɒn/ (SIL-ik-on)
Allotropes	see Allotropes of silicon
Appearance	crystalline, reflective with bluish-tinged faces
Standard atomic weight Ar, std(Si)	[28.084, 28.086] conventional: 28.085
Silicon in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson C ↑ Si ↓ Ge aluminium ← silicon → phosphorus
Atomic number (Z)	14
Group	group 14 (carbon group)
Period	period 3
Block	p-block
Electron configuration	[Ne] 3s2 3p2
Electrons per shell	2, 8, 4
Physical properties
Phase at STP	solid
Melting point	1687 K ​(1414 °C, ​2577 °F)
Boiling point	3538 K ​(3265 °C, ​5909 °F)
Density (near r.t.)	2.3290 g/cm3
when liquid (at m.p.)	2.57 g/cm3
Heat of fusion	50.21 kJ/mol
Heat of vaporization	383 kJ/mol
Molar heat capacity	19.789 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 1908 2102 2339 2636 3021 3537
Atomic properties
Oxidation states	−4, −3, −2, −1, 0, +1, +2, +3, +4 (an amphoteric oxide)
Electronegativity	Pauling scale: 1.90
Ionization energies	1st: 786.5 kJ/mol 2nd: 1577.1 kJ/mol 3rd: 3231.6 kJ/mol (more)
Atomic radius	empirical: 111 pm
Covalent radius	111 pm
Van der Waals radius	210 pm
Spectral lines of silicon
Other properties
Natural occurrence	primordial
Crystal structure	​face-centered diamond-cubic
Speed of sound thin rod	8433 m/s (at 20 °C)
Thermal expansion	2.6 µm/(m⋅K) (at 25 °C)
Thermal conductivity	149 W/(m⋅K)
Electrical resistivity	2.3×103 Ω⋅m (at 20 °C)
Band gap	1.12 eV (at 300 K)
Magnetic ordering	diamagnetic
Molar magnetic susceptibility	−3.9·10−6 cm3/mol (298 K)
Young's modulus	130–188 GPa
Shear modulus	51–80 GPa
Bulk modulus	97.6 GPa
Poisson ratio	0.064–0.28
Mohs hardness	6.5
CAS Number	7440-21-3
History
Naming	after Latin 'silex' or 'silicis', meaning flint
Prediction	Antoine Lavoisier (1787)
Discovery and first isolation	Jöns Jacob Berzelius (1823)
Named by	Thomas Thomson (1817)
Main isotopes of silicon
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct 28Si 92.2% stable 29Si 4.7% stable 30Si 3.1% stable 31Si trace 2.62 h β− 31P 32Si trace 153 y β− 32P

Small grains of silicon because it has been crushed. This is not the silicon used in computers.

A thin cut of a large crystal of silicon that is very smooth. This is the type of silicon can be used in computers because it is very pure.

Silicon looks like a metal, but cannot do everything that a metal can, like conduct electricity well. Silicon is used a lot in today's computers and nearly every other electronic device as well. Germanium can also be used in computers, but silicon is much easier to find.

For example, all of the sand found at the beach is made of small cubes of silicon dioxide also known as silica. Glass is made by heating sand hot enough until it melts. Glass made from silicon can be made in different colours by adding colouring compounds. Many rocks and minerals are composed of compounds of silicon and oxygen called silicates.

Silicon in computers

Silicon is a semiconductor, and much used in computers. A super-pure isotope of silicon, silicon-28, can now be made 40 times more pure than before. It is very important for the next big development in computers. This stores "qubits" in atoms of another element, like phosphorous, embedded in a tiny layer of ultra-pure silicon-28. These qubits can simultaneously encode a one and a zero, for incredibly fast and complex calculations.

Related pages

• List of common elements