silicon

silicon. A chemical element with the symbol Si and atomic number 14, it is a hard, brittle crystalline solid with a blue-grey metallic lustre. It is a member of group 14 in the periodic table, below carbon and above germanium, and is classified as a metalloid. It is the second most abundant element in the Earth's crust, after oxygen, and is a fundamental material in modern technology, most notably as the primary semiconductor used in integrated circuits for the electronics industry.

Properties

At room temperature, it is relatively inert but reacts with halogens and dilute alkalis. Its most common allotropes are crystalline and amorphous, with the crystalline form having a diamond cubic crystal structure similar to that of diamond. Its electrical conductivity can be precisely controlled by adding small amounts of other elements, a process known as doping, which is essential for creating semiconductor devices. The element forms a wide variety of compounds, most notably with oxygen to create silicon dioxide (silica) and with other elements to form silicate minerals and organosilicon compounds like silicones.

Occurrence and production

It is never found free in nature but is widely distributed in the form of silica and silicates, which constitute the majority of the Earth's crust and mantle. Common minerals include quartz, feldspar, mica, and clay. The primary commercial source is silicon dioxide in the form of sand or quartzite, which is reduced in industrial-scale electric arc furnaces using carbon electrodes, a method pioneered by companies like Elkem. For electronic applications, ultra-pure monocrystalline silicon is produced via the Czochralski process or the float-zone silicon technique, with major producers including Hemlock Semiconductor and Wacker Chemie.

Applications

Its most critical use is in the semiconductor industry, where hyper-pure wafers form the substrate for microprocessors, memory chips, and photovoltaic cells in solar panels. The silicon valley region in California is synonymous with this technological revolution. In metallurgy, it is a key component of aluminium alloys and ferrosilicon, used in steelmaking and cast iron production. Compounds like silicon carbide are vital abrasives, while silicon dioxide is the primary ingredient in glass and a raw material for Portland cement. Silicone polymers, with backbones of silicon and oxygen, are used in sealants, adhesives, lubricants, and medical implants.

Biological role

While not considered an essential element for most animals, it is crucial for the development of some plants, certain diatoms, and sponges, which use it to construct their cell walls and skeletons. In humans, it is present in connective tissues like bone, cartilage, and aorta, though its precise metabolic role remains under study. Some research, including work at the University of California, Los Angeles, suggests it may be involved in bone mineralization and the synthesis of collagen.

History

Its compounds have been used since antiquity in the form of flint tools and clay pottery. In 1787, Antoine Lavoisier suspected the existence of a new earth in silica. The element was first isolated in impure form in 1824 by the Swedish chemist Jöns Jacob Berzelius by heating potassium fluorosilicate with potassium metal. Its modern, crystalline form was first prepared in 1854 by Henri Étienne Sainte-Claire Deville via electrolysis. The development of the transistor at Bell Labs in 1947, which utilized silicon and germanium, ushered in the Information Age. Subsequent innovations like the planar process by Jean Hoerni at Fairchild Semiconductor and the integrated circuit by Robert Noyce solidified its dominance in electronics.

Category:Chemical elements Category:Metalloids Category:Semiconductor materials