Silicon is a chemical element with symbol Si and atomic number 14. It is a hard and brittle crystalline solid with a blue-grey metallic lustre; and it is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic table: carbon is above it; and germanium, tin, and lead are below it. It is relatively unreactive. Because of its large chemical affinity for oxygen, it was not until 1823 that Jöns Jakob Berzelius was first able to prepare it and characterize it in pure form. Its melting and boiling points of 1414 °C and 3265 °C respectively are the second-highest among all the metalloids and nonmetals, being only surpassed by boron. Silicon is the eighth most common element in the universe by mass, but very rarely occurs as the pure element in the Earth's crust. It is most widely distributed in dusts, sands, planetoids, and planets as various forms of silicon dioxide (silica) or silicates. Over 90% of the Earth's crust is composed of silicate minerals, making silicon the second most abundant element in the Earth's crust (about 28% by mass) after oxygen.
Silicon, 14SiGeneral propertiesPronunciation/ˈsɪlɪkən/ (SIL-ə-kən)Appearancecrystalline, reflective with bluish-tinged facesStandard atomic weight (Ar, standard)[28.084, 28.086] conventional: 28.085Silicon in the periodic table
(element)
C
↑
Si
↓
Gealuminium ← silicon → phosphorusAtomic number (Z)14Groupgroup 14 (carbon group)Periodperiod 3Blockp-blockElement category metalloidElectron configuration[Ne] 3s2 3p2
Electrons per shell
2, 8, 4Physical propertiesPhase at STPsolidMelting point1687 K (1414 °C, 2577 °F)Boiling point3538 K (3265 °C, 5909 °F)Density (near r.t.)2.3290 g/cm3when liquid (at m.p.)2.57 g/cm3Heat of fusion50.21 kJ/molHeat of vaporization383 kJ/molMolar heat capacity19.789 J/(mol·K)Vapor pressure
P (Pa)1101001 k10 k100 kat T (K)190821022339263630213537
Atomic propertiesOxidation states−4, −3, −2, −1, +1[1] +2, +3, +4(an amphoteric oxide)ElectronegativityPauling scale: 1.90Ionization energies
1st: 786.5 kJ/mol
2nd: 1577.1 kJ/mol
3rd: 3231.6 kJ/mol
(more)
Atomic radiusempirical: 111 pmCovalent radius111 pmVan der Waals radius210 pm

Spectral lines of silicon
