Silicon

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Jöns Jacob Berzelius

MOSFET Structure

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Ferrosilicon

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Silicon wafer with mirror finish

Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and 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. Silicon is the second most abundant element in the Earth's crust (about 28% by mass) after oxygen.

Properties

Silicon is a metalloid, meaning it has properties of both metals and non-metals. It is relatively unreactive. Because of its high chemical affinity for oxygen, it was not until 1823 that Jöns Jacob Berzelius was able to prepare it in its amorphous form; its more common crystalline form was not prepared until 31 years later, by Deville. Silicon's thermal conductivity is high in comparison to other materials, which makes it valuable in the manufacture of semiconductor devices for electronics and solar cells. Its electrical conductivity can be controlled by adding impurities, a process known as doping.

Occurrence

Silicon makes up 27.7% of the Earth's crust by mass and is the second most abundant element, exceeded only by oxygen. It is found in the form of silicon dioxide (quartz), and its compounds are also found in minerals such as feldspars and micas. Silicon does not occur uncombined in nature but occurs chiefly as the oxide (silica) and as silicates. The most common form of silica is quartz, and the Earth's crust is 59% silica.

Uses

Silicon is used primarily in the production of glass, cement, and ceramics. It is also a fundamental constituent in the electronics industry, being the primary material used to manufacture semiconductors. Due to its semiconductor properties, silicon is used in a variety of electronic devices, including transistors, solar cells, and integrated circuits. Silicon chips are the foundation of modern electronic and information technology industries. Additionally, silicon is used in the production of synthetic polymers such as silicone rubber, enhancing their properties of heat resistance and water resistance.

Biological Role

Although silicon is not considered an essential element for the biology of any known living organisms, it plays a significant role in the biology of plants, diatoms, and some animals, where it is used in the formation of structural components or biomineralization. For example, diatoms use silicon to form their cell walls, and some plants use it to strengthen their stem structure.

Environmental Impact

Silicon, in its various forms, has a limited environmental impact. Silicon compounds, such as silicon dioxide, are largely inert and do not pose significant hazards to the environment or to human health. However, the mining and processing of silicon-containing minerals and the manufacturing of silicon-based products can have environmental impacts, including habitat destruction and pollution.

See Also

• Semiconductor
• Silicon dioxide
• Silicon Valley
• Doping (semiconductor)

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