- Key People:
- Jöns Jacob Berzelius
- Frederick Mark Becket
silicon
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What is silicon?
Silicon (Si) is a nonmetallic chemical element in the carbon family and constitutes 27.7% of Earth's crust, second only to oxygen in abundance. The name silicon comes from the Latin word silex, meaning flint.
Pure silicon is a hard, dark gray solid with a metallic luster and an octahedral crystalline structure. It is relatively inactive at normal temperatures but reacts when heated with halogens to form halides and with certain metals to form silicides. It has three stable isotopes: silicon-28 (92.21%), silicon-29 (4.70%), and silicon-30 (3.09%).
Silicon is a semiconductor and is used in computer chips, integrated circuits, transistors, and other electronic devices. Lower purity silicon is used in metallurgy, and silicon compounds are used to make concrete, bricks, glass, and ceramics.
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Where is silicon found in nature?
Silicon, the second most abundant element in Earth's crust, is rarely found in its pure form due to its reactivity. Instead, it is commonly found in combination with oxygen as silica ((SiO_2), silicon dioxide) or with oxygen and other elements in silicates.
These compounds are prevalent in most rocks, sand, clays, and soils. Silicon dioxide is found in crystalline minerals such as quartz, cristobalite, and tridymite, as well as amorphous minerals like agate, opal, and chalcedony. Silicates, characterized by their structural complexity and wide distribution, include minerals like clays, feldspar, olivine, pyroxene, amphiboles, micas, and zeolites. Silicon compounds are also present in natural waters, the atmosphere (as siliceous dust), plants, and some animals.
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What are the main uses of silicon?
Silicon is a crucial semiconductor in electronics due to its atomic structure. Doping it with elements like boron or arsenic allows it to be used in computer chips, integrated circuits, transistors, silicon diodes, liquid crystal displays, and other electronic devices.
Lesser purity silicon is used in metallurgy as a reducing agent and as an alloying element in steel, aluminum, brass, and bronze. Silicon compounds like silica are used to make concrete, bricks, and glass. Silicones, synthetic organosilicon oxides, are used as lubricants, hydraulic fluids, and waterproofing compounds.
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Why is silicon important in making electronics?
Silicon is an extremely important semiconductor in the electronics and technology sectors because of its atomic structure. Doping silicon with elements like boron, phosphorus, or arsenic allows it to be used in computer chips, integrated circuits, transistors, silicon diodes and other electronic devices. Silicon is preferred over other materials like germanium because it is more abundant and retains its semiconducting properties at higher temperatures. Moreover, silicon forms an oxide film that acts as an electrical insulator, which is crucial for creating tiny transistors and other electronic components.
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What are some natural forms and compounds of silicon?
Silicon, the second most abundant element in Earth's crust, is rarely found in its pure form due to its reactivity. It is a cosmic product of alpha-particle absorption.
Silicon is commonly found in combination with oxygen as silica ((SiO_2), silicon dioxide) or with oxygen and other elements like aluminum, magnesium, calcium, sodium, potassium, or iron as silicates. Silica occurs in crystalline minerals such as quartz, cristobalite, and tridymite, and in amorphous forms like agate, opal, and chalcedony. Silicates are abundant and structurally complex, incorporating elements from Groups 1–6, 13, and 17 of the periodic table.
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How is silicon purified and turned into materials for technology?
Silicon purification and its transformation into technological materials involves several steps. Initially, silicon dioxide ((SiO_2)) is reduced with coke in an electric furnace to produce commercial-grade silicon, which is then further refined. For use in electronic devices, extremely pure silicon is required, with less than 1 dopant atom per 10 billion silicon atoms.
The Czochralski method is used to grow single crystals:
1. Electronic-grade silicon is melted in a quartz crucible at approximately 1,500 °C (2,700 °F).
2. Dopants like phosphorus, arsenic, or boron are added at a concentration of a few parts per billion.
3. A seed crystal is lowered into the molten silicon, and the rod and crucible are rotated in opposite directions while being slowly withdrawn, allowing a single crystal to grow.
4. The resulting ingot is sliced into thin wafers, polished, and used to fabricate computer chips, integrated circuits, transistors, and other electronic devices.Float zoning is another method used to produce ultrapure silicon. A vertical silicon rod is held by end clamps, and a short molten zone is created by induction heating and moved along the rod, with surface tension holding the liquid in place.
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News •
silicon (Si), 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.
| atomic number | 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/cm3 |
| oxidation state | −4, (+2), +4 |
| electron configuration | 1s22s22p63s23p2 |
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 109 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.
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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.
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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.