SI

Silicon, with the chemical symbol Si and atomic number 14, is a member of the group of elements known as metalloids. It is a semiconductor and occurs in multiple crystalline forms, most notably as a diamond-like lattice in its crystalline form. Silicon is the second most abundant element in the Earth's crust by mass, after oxygen, making up about 28% of crustal material. It is not found in free form in nature but is most commonly found in silicate minerals and as silica (SiO2) in sands, quartz, and rocks.

Physical and chemical properties: Silicon has a high melting point (about 1414°C) and boiling point (around 2900°C). In its pure form it is relatively brittle but can be manufactured into highly pure monocrystalline or polycrystalline wafers used in electronics. Its crystalline form adopts a diamond cubic crystal structure, which contributes to its semiconducting behavior. Silicon forms a wide range of compounds, including silicon dioxide (SiO2), silicon carbide (SiC), silanes (SiH4), and halides such as silicon tetrachloride (SiCl4). Its most common oxidation state in compounds is +4.

Isotopes and occurrence: Silicon has three stable isotopes: 28Si, 29Si, and 30Si, with natural abundances of about 92.2%, 4.7%, and 3.1%, respectively. It is predominantly extracted from silicon dioxide via reduction with carbon, typically in electric arc furnaces to produce metallurgical grade silicon, which is then refined to purer forms such as polysilicon for electronic use.

Applications: The most prominent uses are in semiconductors and solar cells, where silicon wafers form the basis of integrated circuits and photovoltaic devices. Silicon compounds are also essential in glassmaking, ceramics, cement, and silicones.

History and name: Silicon was identified as an element by Jöns Jakob Berzelius in 1824. The name derives from the Latin silex, silex, meaning flint. Safety considerations include the health hazards of silica dust, which can cause respiratory disease with prolonged exposure.