Silicon

Jai Ganesh · 2025-05-28 23:03:25

Silicon

Gist

Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor.

The element silicon is used extensively as a semiconductor in solid-state devices in the computer and microelectronics industries. For this, hyperpure silicon is needed. The silicon is selectively doped with tiny amounts of boron, gallium, phosphorus or As to control its electrical properties.

Summary

Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a member of group 14 in the periodic table: carbon is above it; and germanium, tin, lead, and flerovium are below it. It is relatively unreactive. Silicon is a significant element that is essential for several physiological and metabolic processes in plants. Silicon is widely regarded as the predominant semiconductor material due to its versatile applications in various electrical devices such as transistors, solar cells, integrated circuits, and others. These may be due to its significant band gap, expansive optical transmission range, extensive absorption spectrum, surface roughening, and effective anti-reflection coating.

Because of its high 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 oxides form a family of anions known as silicates. Its melting and boiling points of 1414 °C and 3265 °C, respectively, are the second highest among all the metalloids and nonmetals, being surpassed only by boron.

Silicon is the eighth most common element in the universe by mass, but very rarely occurs in its pure form in the Earth's crust. It is widely distributed throughout space in cosmic dusts, planetoids, and planets as various forms of silicon dioxide (silica) or silicates. More than 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.

Most silicon is used commercially without being separated, often with very little processing of the natural minerals. Such use includes industrial construction with clays, silica sand, and stone. Silicates are used in Portland cement for mortar and stucco, and mixed with silica sand and gravel to make concrete for walkways, foundations, and roads. They are also used in whiteware ceramics such as porcelain, and in traditional silicate-based soda–lime glass and many other specialty glasses. Silicon compounds such as silicon carbide are used as abrasives and components of high-strength ceramics. Silicon is the basis of the widely used synthetic polymers called silicones.

The late 20th century to early 21st century has been described as the Silicon Age (also known as the Digital Age or Information Age) because of the large impact that elemental silicon has on the modern world economy. The small portion of very highly purified elemental silicon used in semiconductor electronics (<15%) is essential to the transistors and integrated circuit chips used in most modern technology such as smartphones and other computers. In 2019, 32.4% of the semiconductor market segment was for networks and communications devices, and the semiconductors industry is projected to reach $726.73 billion by 2027.

Silicon is an essential element in biology. Only traces are required by most animals, but some sea sponges and microorganisms, such as diatoms and radiolaria, secrete skeletal structures made of silica. Silica is deposited in many plant tissues.

Details

Silicon (Si) is a nonmetallic chemical element in the carbon family (Group 14 [IVa] of the periodic table). Silicon makes up 27.7 percent of Earth’s crust; it is the second most abundant element in the crust, being surpassed only by oxygen.

The name silicon derives from the Latin silex or silicis, meaning “flint” or “hard stone.” Amorphous elemental silicon was first isolated and described as an element in 1824 by Jöns Jacob Berzelius, a Swedish chemist. Impure silicon had already been obtained in 1811. Crystalline elemental silicon was not prepared until 1854, when it was obtained as a product of electrolysis. In the form of rock crystal, however, silicon was familiar to the predynastic Egyptians, who used it for beads and small vases; to the early Chinese; and probably to many others of the ancients. The manufacture of glass containing silica was carried out both by the Egyptians—at least as early as 1500 bce—and by the Phoenicians. Certainly, many of the naturally occurring compounds called silicates were used in various kinds of mortar for construction of dwellings by the earliest people.

Element Properties

atomic numbe : 14
atomic weight : 28.086
melting point : 1,410 °C (2,570 °F)
boiling point : 3,265 °C (5,909 °F)
density : 2.33 grams/{cm}^3
oxidation state : −4, (+2), +4

Occurrence and distribution

On a weight basis, the abundance of silicon in the crust of Earth is exceeded only by oxygen. Estimates of the cosmic abundance of other elements often are cited in terms of the number of their atoms per 106 atoms of silicon. Only hydrogen, helium, oxygen, neon, nitrogen, and carbon exceed silicon in cosmic abundance. Silicon is believed to be a cosmic product of alpha-particle absorption, at a temperature of about {10}^{9} K, by the nuclei of carbon-12, oxygen-16, and neon-20. The energy binding the particles that form the nucleus of silicon is about 8.4 million electron volts (MeV) per nucleon (proton or neutron). Compared with the maximum of about 8.7 million electron volts for the nucleus of iron, almost twice as massive as that of silicon, this figure indicates the relative stability of the silicon nucleus.

Pure silicon is too reactive to be found in nature, but it is found in practically all rocks as well as in sand, clays, and soils, combined either with oxygen as silica (SiO2, silicon dioxide) or with oxygen and other elements (e.g., aluminum, magnesium, calcium, sodium, potassium, or iron) as silicates. The oxidized form, as silicon dioxide and particularly as silicates, is also common in Earth’s crust and is an important component of Earth’s mantle. Its compounds also occur in all natural waters, in the atmosphere (as siliceous dust), in many plants, and in the skeletons, tissues, and body fluids of some animals.

In compounds, silicon dioxide occurs both in crystalline minerals (e.g., quartz, cristobalite, tridymite) and amorphous or seemingly amorphous minerals (e.g., agate, opal, chalcedony) in all land areas. The natural silicates are characterized by their abundance, wide distribution, and structural and compositional complexities. Most of the elements of the following groups in the periodic table are found in silicate minerals: Groups 1–6, 13, and 17 (I–IIIa, IIIb–VIb, and VIIa). These elements are said to be lithophilic, or stone-loving. Important silicate minerals include the clays, feldspar, olivine, pyroxene, amphiboles, micas, and zeolites.

Properties of the element

Elemental silicon is produced commercially by the reduction of silica (SiO2) with coke in an electric furnace, and the impure product is then refined. On a small scale, silicon can be obtained from the oxide by reduction with aluminum. Almost pure silicon is obtained by the reduction of silicon tetrachloride or trichlorosilane. For use in electronic devices, single crystals are grown by slowly withdrawing seed crystals from molten silicon.

Pure silicon is a hard, dark gray solid with a metallic lustre and with a octahedral crystalline structure the same as that of the diamond form of carbon, to which silicon shows many chemical and physical similarities. The reduced bond energy in crystalline silicon renders the element lower melting, softer, and chemically more reactive than diamond. A brown, powdery, amorphous form of silicon has been described that also has a microcrystalline structure.

Because silicon forms chains similar to those formed by carbon, silicon has been studied as a possible base element for silicon organisms. The limited number of silicon atoms that can catenate, however, greatly reduces the number and variety of silicon compounds compared with those of carbon. The oxidation–reduction reactions do not appear to be reversible at ordinary temperatures. Only the 0 and +4 oxidation states of silicon are stable in aqueous systems.

Silicon, like carbon, is relatively inactive at ordinary temperatures; but when heated it reacts vigorously with the halogens (fluorine, chlorine, bromine, and iodine) to form halides and with certain metals to form silicides. As is true with carbon, the bonds in elemental silicon are strong enough to require large energies to activate, or promote, reaction in an acidic medium, so it is unaffected by acids except hydrofluoric. At red heat, silicon is attacked by water vapour or by oxygen, forming a surface layer of silicon dioxide. When silicon and carbon are combined at electric furnace temperatures (2,000–2,600 °C [3,600–4,700 °F]), they form silicon carbide (carborundum, SiC), which is an important abrasive. With hydrogen, silicon forms a series of hydrides, the silanes. When combined with hydrocarbon groups, silicon forms a series of organic silicon compounds.

Three stable isotopes of silicon are known: silicon-28, which makes up 92.21 percent of the element in nature; silicon-29, 4.70 percent; and silicon-30, 3.09 percent. Five radioactive isotopes are known.

Elemental silicon and most silicon-containing compounds appear to be nontoxic. Indeed, human tissue often contains 6 to 90 milligrams of silica (SiO2) per 100 grams dry weight, and many plants and lower forms of life assimilate silica and use it in their structures. Inhalation of dusts containing alpha SiO2, however, produces a serious lung disease called silicosis, common among miners, stonecutters, and ceramic workers, unless protective devices are used.

Uses

Silicon’s atomic structure makes it an extremely important semiconductor, and silicon is the most important semiconductor in the electronics and technology sector. Addition of an element such as boron, an atom of which can be substituted for a silicon atom in the crystal structure but which provides one less valence electron (boron is an acceptor atom) than silicon, allows silicon atoms to lose electrons to it. The positive holes created by the shift in electrons allow extrinsic semiconduction of a type referred to as positive (p). Addition of an element such as math, an atom of which can also be substituted for a silicon atom in the crystal but which provides an extra valence electron (math is a donor atom), releases its electron within the lattice. These electrons allow semiconduction of the negative (n) type. Highly purified silicon, doped (infused) with such elements as boron, phosphorus, and math, is commonly known as a silicon wafer and is the basic material used in computer chips, integrated circuits, transistors, silicon diodes, liquid crystal displays, and various other electronic and switching devices.

If p-silicon and n-silicon wafers are joined, in a manner called the p–n junction, and placed in sunlight, the absorbed energy causes electrons to move across the junction and an electric current to flow in an external circuit connecting the two wafers. Such a solar cell is a source of energy for space devices and is found in solar power arrays as a source of renewable energy.

Silicon of lesser purity is used in metallurgy as a reducing agent and as an alloying element in steel, aluminum, brass, and bronze. The most important compounds of silicon are the dioxide (silica) and the various silicates. Silica in the form of sand and clay is used to make concrete and bricks as well as refractory materials for high-temperature applications. As the mineral quartz, the compound may be softened by heating and shaped into glassware. Silica (silicon dioxide) is useful as an abrasive, in the production of glass and other ceramic bodies, and as an adsorbent. Silicates, most of which are insoluble in water, are employed in making glass as well as in the fabrication of enamels, pottery, china, and other ceramic materials. Sodium silicates, commonly known as water glass, or silicate of soda, are used in soaps, in the treatment of wood to prevent decay, for the preservation of eggs, as a cement, and in dyeing. Both naturally occurring and synthetically produced silicates are important in building materials, absorbents, and ion exchangers. Silicones are synthetic organosilicon oxides composed of the elements silicon, oxygen, carbon, and hydrogen; they are used as lubricants, hydraulic fluids, waterproofing compounds, varnishes, and enamels because, as a class, they are chemically inert and unusually stable at high temperatures.

China, Russia, Norway, and Brazil are the largest producers of silicon minerals.

Additional Information:

Appearance

The element, when ultrapure, is a solid with a blue-grey metallic sheen.

Uses

Silicon is one of the most useful elements to mankind. Most is used to make alloys including aluminium-silicon and ferro-silicon (iron-silicon). These are used to make dynamo and transformer plates, engine blocks, cylinder heads and machine tools and to deoxidise steel.

Silicon is also used to make silicones. These are silicon-oxygen polymers with methyl groups attached. Silicone oil is a lubricant and is added to some cosmetics and hair conditioners. Silicone rubber is used as a waterproof sealant in bathrooms and around windows, pipes and roofs.

The element silicon is used extensively as a semiconductor in solid-state devices in the computer and microelectronics industries. For this, hyperpure silicon is needed. The silicon is selectively doped with tiny amounts of boron, gallium, phosphorus or math to control its electrical properties.

Granite and most other rocks are complex silicates, and these are used for civil engineering projects. Sand (silicon dioxide or silica) and clay (aluminium silicate) are used to make concrete and cement. Sand is also the principal ingredient of glass, which has thousands of uses. Silicon, as silicate, is present in pottery, enamels and high-temperature ceramics.

Silicon carbides are important abrasives and are also used in lasers.

Biological role

Silicon is essential to plant life but its use in animal cells is uncertain. Phytoliths are tiny particles of silica that form within some plants. Since these particles do not rot they remain in fossils and provide us with useful evolutionary evidence.

Silicon is non-toxic but some silicates, such as asbestos, are carcinogenic. Workers, such as miners and stonecutters, who are exposed to siliceous dust can develop a serious lung disease called silicosis.

Natural abundance

Silicon makes up 27.7% of the Earth’s crust by mass and is the second most abundant element (oxygen is the first). It does not occur uncombined in nature but occurs chiefly as the oxide (silica) and as silicates. The oxide includes sand, quartz, rock crystal, amethyst, agate, flint and opal. The silicate form includes asbestos, granite, hornblende, feldspar, clay and mica.

Elemental silicon is produced commercially by reducing sand with carbon in an electric furnace. High-purity silicon, for the electronics industry, is prepared by the thermal decomposition of ultra-pure trichlorosilane, followed by recrystallisation.

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#1 2025-05-28 23:03:25

Silicon

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