View source for Chemistry:Silicon

{{Short description|Chemical element with atomic number 14}}
{{Infobox silicon}}
'''Silicon''' is a [[Chemistry:Chemical element|chemical element]]; it has [[Chemistry:Symbol|symbol]] '''Si''' and [[Physics:Atomic number|atomic number]] 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a [[Chemistry:Tetravalence|tetravalent]] [[Chemistry:Metalloid|metalloid]] and [[Physics:Semiconductor|semiconductor]]. It is a member of [[Chemistry:Carbon group|group 14]] in the periodic table: [[Chemistry:Carbon|carbon]] is above it; and [[Chemistry:Germanium|germanium]], [[Chemistry:Tin|tin]], [[Chemistry:Lead|lead]], and [[Chemistry:Flerovium|flerovium]] are below it. It is relatively unreactive.

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 [[Chemistry:Oxide|oxide]]s form a family of anions known as [[Chemistry:Silicate|silicate]]s. Its melting and boiling points of 1414&nbsp;°C and 3265&nbsp;°C, respectively, are the second highest among all the metalloids and nonmetals, being surpassed only by [[Chemistry:Boron|boron]].{{efn|Although [[Chemistry:Carbon|carbon]] remains solid at higher temperatures than silicon, it [[Sublimation (phase transition)|sublimes]] at [[Physics:Atmospheric pressure|atmospheric pressure]] instead of melting and boiling, so it has no melting point and boiling point.}}

Silicon is the eighth [[Chemistry:Abundance of the chemical elements|most common element]] in the universe by mass, but very rarely occurs as the pure element in the Earth's crust. It is widely distributed in space in cosmic dusts, [[Astronomy:Minor planet|planetoids]], and [[Astronomy:Planet|planet]]s as various forms of [[Chemistry:Silicon dioxide|silicon dioxide]] (silica) or [[Chemistry:Silicate|silicate]]s. More than 90% of the Earth's crust is composed of [[Chemistry:Silicate minerals|silicate minerals]], making silicon the [[Earth:Abundance of elements in Earth's crust|second most abundant element]] in the Earth's crust (about 28% by mass), after [[Chemistry:Oxygen|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 [[Earth:Gravel|gravel]] to make [[Chemistry:Concrete|concrete]] for walkways, foundations, and roads. They are also used in whiteware ceramics such as [[Chemistry:Porcelain|porcelain]], and in traditional [[Chemistry:Silicate|silicate]]-based [[Engineering:Soda–lime glass|soda–lime glass]] and many other specialty [[Chemistry:Glass|glass]]es. Silicon compounds such as [[Chemistry:Silicon carbide|silicon carbide]] are used as abrasives and components of high-strength ceramics. Silicon is the basis of the widely used synthetic polymers called [[Chemistry:Silicone|silicone]]s.

The late 20th century to early 21st century has been described as the Silicon Age (also known as the Digital Age or [[Philosophy:Information Age|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 [[Engineering:Integrated circuit|integrated circuit]] chips used in most modern technology such as [[Engineering:Smartphone|smartphone]]s and other [[Computer|computer]]s. 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.<ref>{{harvnb|Kamal|2022}}</ref>

Silicon is an essential element in biology. Only traces are required by most animals, but some sea sponges and microorganisms, such as diatoms and [[Biology:Radiolaria|radiolaria]], secrete skeletal structures made of silica. Silica is deposited in many plant tissues.<ref name="Cutter">{{cite book|last=Cutter|first=Elizabeth G.|title=Plant Anatomy. Part 1 Cells and Tissues|edition=2nd |publisher=Edward Arnold|place=London|date=1978|isbn=978-0-7131-2639-6}}</ref>

==History==
Owing to the abundance of silicon in the [[Earth:Earth's crust|Earth's crust]], natural silicon-based materials have been used for thousands of years. Silicon rock crystals were familiar to various ancient civilizations, such as the predynastic Egyptians who used it for beads and small vases, as well as the ancient Chinese. [[Chemistry:Glass|Glass]] containing [[Chemistry:Silica|silica]] was manufactured by the Egyptians since at least 1500 BC, as well as by the ancient Phoenicians. Natural [[Chemistry:Silicate|silicate]] compounds were also used in various types of mortar for construction of early human dwellings.<ref name="Britannica">{{cite web |title=Silicon |url=https://www.britannica.com/science/silicon |website=Encyclopedia Britannica |access-date=22 August 2019}}</ref>

===Discovery===
[[File:Jöns Jacob Berzelius.jpg|thumb|left|upright|Jöns Jacob Berzelius discovered the silicon element in 1823.]]
In 1787, [[Biography:Antoine Lavoisier|Antoine Lavoisier]] suspected that [[Chemistry:Silica|silica]] might be an oxide of a fundamental [[Chemistry:Chemical element|chemical element]],<ref>In his table of the elements, Lavoisier listed five "salifiable earths", ''i.e.'', ores that could be made to react with acids to produce salts (''salis'' = salt, in Latin): ''chaux'' (calcium oxide), ''magnésie'' (magnesia, magnesium oxide), ''baryte'' (barium sulfate), ''alumine'' (alumina, aluminium oxide), and ''silice'' (silica, silicon dioxide). About these "elements", Lavoisier speculates: "We are probably only acquainted as yet with a part of the metallic substances existing in nature, as all those which have a stronger affinity to oxygen than carbon possesses, are incapable, hitherto, of being reduced to a metallic state, and consequently, being only presented to our observation under the form of oxyds, are confounded with earths. It is extremely probable that barytes, which we have just now arranged with earths, is in this situation; for in many experiments it exhibits properties nearly approaching to those of metallic bodies. It is even possible that all the substances we call earths may be only metallic oxyds, irreducible by any hitherto known process." – from {{cite book|url=https://archive.org/details/elementschemist00kerrgoog/page/n217 |page= 218 |author=Lavoisier |translator= Robert Kerr |title=Elements of Chemistry|edition= 4 |location=Edinburgh, Scotland|publisher= William Creec|year= 1799}} (The original passage appears in: {{cite book|author=Lavoisier|title=Traité Élémentaire de Chimie|location=Paris|publisher= Cuchet |year=1789|volume=1|url= {{google books |plainurl=y |id=hZch3yOrayUC|page=174}} |page=174}}</ref> but the [[Chemistry:Chemical affinity|chemical affinity]] of silicon for oxygen is high enough that he had no means to reduce the oxide and isolate the element.{{sfn|Greenwood|Earnshaw|1997|p=328}} After an attempt to isolate silicon in 1808, Sir Humphry Davy proposed the name "silicium" for silicon, from the Latin ''silex'',<!-- Dictionary.com Unabridged (v 1.1) - Cite This Source si·lex –noun flint; silica. [Origin: 1585–95; < L silex, s. silic- hard stone, flint, boulder] --> ''silicis'' for flint, and adding the "-ium" ending because he believed it to be a metal.<ref>{{Cite journal|url={{google books |plainurl=y |id=Kg9GAAAAMAAJ|page=333}} |title=Electro chemical researches, on the decomposition of the earths; with observations on the metals obtained from the alkaline earths, and on the amalgam procured from ammonia |last=Davy |first=Humphry |date=1808 |publisher=W. Bowyer and J. Nichols |language=en |journal=Philosophical Transactions of the Royal Society of London |volume=98 |pages=333–370}}. On [{{google books |plainurl=y |id=Kg9GAAAAMAAJ|page=353}} p. 353] Davy coins the name "silicium" : "Had I been so fortunate as to have obtained more certain evidences on this subject, and to have procured the metallic substances I was in search of, I should have proposed for them the names of silicium [silicon], alumium [aluminium], zirconium, and glucium [beryllium]."</ref> Most other languages use transliterated forms of Davy's name, sometimes adapted to local phonology (e.g. [[Social:German language|German]] ''Silizium'', [[Social:Turkish language|Turkish]] ''silisyum'', [[Social:Catalan language|Catalan]] ''silici'', [[Social:Armenian language|Armenian]] ''Սիլիցիում'' or ''Silitzioum''). A few others use instead a [[Social:Calque|calque]] of the Latin root (e.g. [[Social:Russian language|Russian]] ''кремний'', from ''кремень'' "flint"; [[Social:Greek language|Greek]] ''πυρίτιο'' from ''πυρ'' "fire"; [[Social:Finnish language|Finnish]] ''pii'' from ''piikivi'' "flint", [[Social:Czech language|Czech]] ''křemík'' from ''křemen'' "quartz", "flint").<ref>{{cite web |url=http://elements.vanderkrogt.net/element.php?sym=si |title=14 Silicon |publisher=Elements.vanderkrogt.net |access-date=2008-09-12}}</ref>

Gay-Lussac and Thénard are thought to have prepared impure [[Chemistry:Amorphous silicon|amorphous silicon]] in 1811, through the heating of recently isolated [[Chemistry:Potassium|potassium]] metal with [[Chemistry:Silicon tetrafluoride|silicon tetrafluoride]], but they did not purify and characterize the product, nor identify it as a new element.<ref>{{Cite book|last1=Gay-Lussac|first1=Joseph Louis|url={{google books |plainurl=y |id=ruITAAAAQAAJ|page=313}}|title=Recherches physico-chimiques, faites sur la pile: sur la préparation chimique et les propriétés du potassium et du sodium; sur la décomposition de l'acide boracique; sur les acides fluorique, muriatique et muriatique oxigéné; sur l'action chimique de la lumière; sur l'analyse végétale et animale, etc|last2=Thénard|first2=Louis Jacques baron|date=1811|publisher=Deterville|language=fr}} [{{google books |plainurl=y |id=ruITAAAAQAAJ|page=313}} pp. 313–314]; vol. 2, [{{google books |plainurl=y |id=w8YPAAAAQAAJ|page=55
}} pp. 55–65].</ref> Silicon was given its present name in 1817 by Scottish chemist Thomas Thomson. He retained part of Davy's name but added "-on" because he believed that silicon was a [[Chemistry:Nonmetal|nonmetal]] similar to [[Chemistry:Boron|boron]] and [[Chemistry:Carbon|carbon]].<ref>{{Cite book|last1=Thomson|first1=Thomas|url=http://archive.org/details/bub_gb_zVA0AQAAMAAJ|title=A system of chemistry : in four volumes|last2=Baldwin|first2=Charles|last3=Blackwood|first3=William|last4=Baldwin|first4=Cradock|last5=Bell & Bradfute|first5=bookseller|last6=Hodges & McArthur|first6=bookseller|date=1817|publisher=London : Printed for Baldwin, Craddock, and Joy, Paternoster-Row; William Blackwood, and Bell and Bradfute, Edinburgh; and Hodges and Macarthur, Dublin|others=University of Wisconsin - Madison|page= 252}}: "The base of silica has been usually considered as a metal, and called ''silicium''. But as there is not the smallest evidence for its metallic nature, and as it bears a close resemblance to boron and carbon, it is better to class it along with these bodies, and to give it the name of ''silicon''."</ref> In 1824, [[Biography:Jöns Jacob Berzelius|Jöns Jacob Berzelius]] prepared amorphous silicon using approximately the same method as Gay-Lussac (reducing [[Chemistry:Potassium fluorosilicate|potassium fluorosilicate]] with molten potassium metal), but purifying the product to a brown powder by repeatedly washing it.<ref>See
* Berzelius announced his discovery of silicon ("silicium") in: Berzelius, J. (presented: 1823; published: 1824) [https://books.google.com/books?id=pJlPAAAAYAAJ&pg=PA46 "Undersökning af flusspatssyran och dess märkvärdigaste föreningar"] (Investigation of hydrofluoric acid and of its most noteworthy compounds), ''Kongliga Vetenskaps-Academiens Handlingar'' [Proceedings of the Royal Science Academy], '''12''' : 46–98. The isolation of silicon and its characterization are detailed in the section titled "Flussspatssyrad kisseljords sönderdelning med kalium," pp. 46–68.
* The above article was printed in German in: J.J. Berzelius (1824) [http://gallica.bnf.fr/ark:/12148/bpt6k15086x/f185.image.langEN "''II. Untersuchungen über Flussspathsäure und deren merkwürdigsten Verbindungen''"] (II. Investigations of hydrofluoric acid and its most noteworthy compounds), ''Annalen der Physik'', '''77''': 169–230. The isolation of silicon is detailed in the section titled: [http://gallica.bnf.fr/ark:/12148/bpt6k15086x/f220.image.langEN "Zersetzung der flussspaths. Kieselerde durch Kalium"] (Decomposition of silicate fluoride by potassium), pp. 204–210.
* The above article was reprinted in French in: Berzelius (1824) [{{google books |plainurl=y |id=eHmstO7CmqAC|page=337}} "Décomposition du fluate de silice par le potassium"] (Decomposition of silica fluoride by potassium), ''Annales de Chimie et de Physique'', '''27''': 337–359.
* Reprinted in English in: {{Cite journal|url={{google books |plainurl=y |id=_UwwAAAAIAAJ|page=254}}|title=On the mode of obtaining silicium, and on the characters and properties of that substance |journal=The Philosophical Magazine and Journal: Comprehending Various Branches of Science, the Liberal and Fine Arts, Agriculture, Manufactures, and Commerce|date=1825|publisher=Richard Taylor and Company|language=en|volume=65 |pages=254–267}}</ref> As a result, he is usually given credit for the element's discovery.<ref>{{cite journal |title =The discovery of the elements: XII. Other elements isolated with the aid of potassium and sodium: beryllium, boron, silicon, and aluminum|last =Weeks |first=Mary Elvira |date=1932 |journal=Journal of Chemical Education|volume=9|issue=8|pages=1386–1412 |bibcode=1932JChEd...9.1386W|doi =10.1021/ed009p1386}}</ref><ref>{{cite journal |date=2007 |journal=Russian Journal of Applied Chemistry |doi=10.1134/S1070427207120397 |title=Silicon era |last1=Voronkov |first1 =M.G. |volume=80|page=2190 |issue=12|s2cid=195240638 }}</ref> The same year, Berzelius became the first to prepare [[Chemistry:Silicon tetrachloride|silicon tetrachloride]]; [[Chemistry:Silicon tetrafluoride|silicon tetrafluoride]] had already been prepared long before in 1771 by [[Biography:Carl Wilhelm Scheele|Carl Wilhelm Scheele]] by dissolving silica in [[Chemistry:Hydrofluoric acid|hydrofluoric acid]].{{sfn|Greenwood|Earnshaw|1997|p=328}} In 1823 for the first time Jacob Berzelius discovered [[Chemistry:Silicon tetrachloride|silicon tetrachloride]] (SiCl<sub>4</sub>).<ref name="Kipping-1937">{{Cite journal |last=Kipping |first=Frederic Stanley |date=1937-03-01 |title=The bakerian lecture organic derivatives of silicon |journal= Proceedings of the Royal Society of London, Series A |volume=159 |issue=896 |pages=139–148 |doi=10.1098/rspa.1937.0063|bibcode=1937RSPSA.159..139K |doi-access=free }}</ref> In 1846 Von Ebelman's synthesized [[Chemistry:Tetraethyl orthosilicate|tetraethyl orthosilicate]] (Si(OC<sub>2</sub>H<sub>5</sub>)<sub>4</sub>).<ref name="Muller1965">{{Cite journal |last=Muller |first=Richard |date=January 1965 |title=One hundred years of organosilicon chemistry |url=https://pubs.acs.org/doi/abs/10.1021/ed042p41 |journal=Journal of Chemical Education |language=en |volume=42 |issue=1 |pages=41 |doi=10.1021/ed042p41 |bibcode=1965JChEd..42...41M |issn=0021-9584}}</ref><ref name="Kipping-1937" />

Silicon in its more common crystalline form was not prepared until 31 years later, by Deville.<ref>In 1854, Deville was trying to prepare aluminium metal from aluminium chloride that was heavily contaminated with silicon chloride. Deville used two methods to prepare aluminium: heating aluminium chloride with sodium metal in an inert atmosphere (of hydrogen); and melting aluminium chloride with sodium chloride and then electrolyzing the mixture. In both cases, pure silicon was produced: the silicon dissolved in the molten aluminium, but crystallized upon cooling. Dissolving the crude aluminium in hydrochloric acid revealed flakes of crystallized silicon. See: Henri Sainte-Claire Deville (1854) [{{google books |plainurl=y |id=C3VFAAAAcAAJ|page=321}} "Note sur deux procédés de préparation de l'aluminium et sur une nouvelle forme du silicium"] (Note on two procedures for the preparation of aluminium and on a new form of silicon), ''Comptes rendus'', '''39''': 321–326.<br />Subsequently, Deville obtained crystalline silicon by heating the chloride or fluoride of silicon with sodium metal, isolating the amorphous silicon, then melting the amorphous form with salt and heating the mixture until most of the salt evaporated. See: {{cite journal|first=H. |last=Sainte-Claire Deville|year=1855|url={{google books |plainurl=y |id=tZhDAQAAIAAJ|page=1034}} |title=Du silicium et du titane (On silicon and titanium) |journal=Comptes rendus |volume=40|pages= 1034–1036}}</ref><ref>{{Cite web|title=Information on silicon – history, thermodynamic, chemical, physical and electronic properties|url=http://ww1.etacude.com/|access-date=2021-06-08|website=Etacude}}</ref> By [[Chemistry:Electrolysis|electrolyzing]] a mixture of [[Chemistry:Sodium chloride|sodium chloride]] and [[Chemistry:Aluminium chloride|aluminium chloride]] containing approximately 10% silicon, he was able to obtain a slightly impure allotrope of silicon in 1854.<ref>{{cite web|url=http://nautilus.fis.uc.pt/st2.5/scenes-e/elem/e01410.html |title=Silicon: History|archive-url=https://web.archive.org/web/20110727141021/http://nautilus.fis.uc.pt/st2.5/scenes-e/elem/e01410.html |archive-date=July 27, 2011|date=2011-07-27 |website=Nautilus.fis.uc.pt}}</ref> Later, more cost-effective methods have been developed to isolate several allotrope forms, the most recent being [[Chemistry:Silicene|silicene]] in 2010.<ref name="Aufray2010">{{Cite journal |last1=Aufray |first1=B. |last2=Kara |first2=A. | last3=Vizzini |first3=S. B. |last4=Oughaddou |first4=H. |last5=LéAndri |first5=C. |last6=Ealet |first6=B. |last7=Le Lay |first7=G. |doi=10.1063/1.3419932 |title=Graphene-like silicon nanoribbons on Ag(110): A possible formation of silicene |journal=Applied Physics Letters |volume=96 |issue=18 |pages=183102 |year=2010 | bibcode=2010ApPhL..96r3102A|url=https://stars.library.ucf.edu/cgi/viewcontent.cgi?article=7963&context=facultybib2010 }}</ref><ref name="Lalmi2010">{{Cite journal |last1=Lalmi |first1=B. |last2=Oughaddou |first2=H. |last3=Enriquez |first3=H. |last4=Kara |first4=A. |last5=Vizzini |first5=S. B. |last6=Ealet |first6=B. N. |last7=Aufray |first7=B. |doi=10.1063/1.3524215 |title=Epitaxial growth of a silicene sheet |journal=Applied Physics Letters |volume=97 |issue=22 |pages=223109 |year=2010 |bibcode=2010ApPhL..97v3109L |arxiv=1204.0523|s2cid=118490651 }}</ref> Meanwhile, research on the chemistry of silicon continued; [[Biography:Friedrich Wöhler|Friedrich Wöhler]] discovered the first volatile hydrides of silicon, synthesising [[Chemistry:Trichlorosilane|trichlorosilane]] in 1857 and [[Chemistry:Silane|silane]] itself in 1858, but a detailed investigation of the [[Chemistry:Silanes|silanes]] was only carried out in the early 20th century by Alfred Stock, despite early speculation on the matter dating as far back as the beginnings of synthetic organic chemistry in the 1830s.{{sfn|Greenwood|Earnshaw|1997|p=330}}<ref>{{harvnb|Greenwood|Earnshaw|1997|pp=337–340}}</ref> Similarly, the first [[Chemistry:Organosilicon compound|organosilicon compound]], tetraethylsilane, was synthesised by Charles Friedel and James Crafts in 1863, but detailed characterisation of organosilicon chemistry was only done in the early 20th century by Frederic Kipping.{{sfn|Greenwood|Earnshaw|1997|p=328}}

Starting in the 1920s, the work of William Lawrence Bragg on [[Physics:X-ray crystallography|X-ray crystallography]] elucidated the compositions of the silicates, which had previously been known from [[Chemistry:Analytical chemistry|analytical chemistry]] but had not yet been understood, together with [[Biography:Linus Pauling|Linus Pauling]]'s development of [[Chemistry:Crystal chemistry|crystal chemistry]] and Victor Goldschmidt's development of [[Chemistry:Geochemistry|geochemistry]]. The middle of the 20th century saw the development of the chemistry and industrial use of [[Chemistry:Siloxane|siloxane]]s and the growing use of [[Chemistry:Silicone|silicone]] [[Chemistry:Polymer|polymer]]s, [[Physics:Elastomer|elastomer]]s, and resins. In the late 20th century, the complexity of the crystal chemistry of [[Chemistry:Silicide|silicide]]s was mapped, along with the [[Physics:Solid-state physics|solid-state physics]] of [[Physics:Doping (semiconductor)|doped]] [[Physics:Semiconductor|semiconductor]]s.{{sfn|Greenwood|Earnshaw|1997|p=328}}

===Silicon semiconductors===
The first semiconductor devices did not use silicon, but used [[Chemistry:Galena|galena]], including German [[Physicist|physicist]] Ferdinand Braun's [[Engineering:Crystal detector|crystal detector]] in 1874 and Indian physicist [[Biography:Jagadish Chandra Bose|Jagadish Chandra Bose]]'s [[Social:Radio|radio]] crystal detector in 1901.<ref name="computerhistory-timeline">{{cite web |title=Timeline |url=https://www.computerhistory.org/siliconengine/timeline/ |website=The Silicon Engine |publisher=Computer History Museum |access-date=22 August 2019}}</ref><ref name="computerhistory-1901">{{cite web |title=1901: Semiconductor Rectifiers Patented as "Cat's Whisker" Detectors |url=https://www.computerhistory.org/siliconengine/semiconductor-rectifiers-patented-as-cats-whisker-detectors/ |website=The Silicon Engine |publisher=Computer History Museum |access-date=23 August 2019}}</ref> The first silicon semiconductor device was a silicon radio crystal detector, developed by American engineer [[Biography:Greenleaf Whittier Pickard|Greenleaf Whittier Pickard]] in 1906.<ref name="computerhistory-1901" />

In 1940, Russell Ohl discovered the [[Physics:P–n junction|p–n junction]] and [[Chemistry:Photovoltaic effect|photovoltaic effect]]s in silicon. In 1941, techniques for producing high-purity [[Chemistry:Germanium|germanium]] and silicon crystals were developed for [[Engineering:Radar|radar]] [[Physics:Microwave|microwave]] detector crystals during [[Social:World War II|World War II]].<ref name="computerhistory-timeline" /> In 1947, physicist [[Biography:William Shockley|William Shockley]] theorized a [[Engineering:Field-effect transistor|field-effect amplifier]] made from germanium and silicon, but he failed to build a working device, before eventually working with germanium instead. The first working transistor was a [[Engineering:Point-contact transistor|point-contact transistor]] built by [[Biography:John Bardeen|John Bardeen]] and Walter Brattain later that year while working under Shockley.<ref>{{cite web |title=1947: Invention of the Point-Contact Transistor |url=https://www.computerhistory.org/siliconengine/invention-of-the-point-contact-transistor/ |website=The Silicon Engine |publisher=Computer History Museum |access-date=23 August 2019}}</ref> In 1954, physical chemist Morris Tanenbaum fabricated the first silicon junction transistor at [[Organization:Bell Labs|Bell Labs]].<ref>{{cite web |title=1954: Morris Tanenbaum fabricates the first silicon transistor at Bell Labs |url=https://www.computerhistory.org/siliconengine/silicon-transistors-offer-superior-operating-characteristics/ |website=The Silicon Engine |publisher=Computer History Museum |access-date=23 August 2019}}</ref> In 1955, Carl Frosch and Lincoln Derick at Bell Labs accidentally discovered that [[Chemistry:Silicon dioxide|silicon dioxide]] ({{chem|SiO|2}}) could be grown on silicon,<ref name="Bassett22">{{cite book |last1=Bassett |first1=Ross Knox |title=To the Digital Age: Research Labs, Start-up Companies, and the Rise of MOS Technology |date=2007 |publisher=Johns Hopkins University Press |isbn=978-0-8018-8639-3 |pages=22–23 |url=https://books.google.com/books?id=UUbB3d2UnaAC&pg=PA22}}</ref> and they later proposed this could mask silicon surfaces during diffusion processes in 1958.<ref name="Saxena">{{cite book |last=Saxena|first=A. |title =Invention of integrated circuits: untold important facts |url ={{google books |plainurl=y |id=z7738Wq-j-8}}|publisher =[[Company:World Scientific|World Scientific]] |series =International series on advances in solid state electronics and technology |year =2009 |isbn =978-981-281-445-6 |pages =96–97}}</ref>

===Silicon Age===
thumb|The [[MOSFET, also known as the MOS transistor, is the key component of the Silicon Age. It was invented by Mohamed M. Atalla and [[Biography:Dawon Kahng|Dawon Kahng]] at [[Organization:Bell Labs|Bell Labs]] in 1959.]]

The "Silicon Age" refers to the late 20th century to early 21st century.<ref name="Feldman">{{cite book |last1=Feldman |first1=Leonard C. |title=Fundamental Aspects of Silicon Oxidation |date=2001 |publisher=Springer Science & Business Media |isbn=978-3-540-41682-1 |pages=1–11 |chapter=Introduction |chapter-url=https://books.google.com/books?id=sV4y2-mWGNIC&pg=PA1}}</ref><ref name="Dabrowski">{{cite book |last1=Dabrowski |first1=Jarek |last2=Müssig |first2=Hans-Joachim |chapter=1.2. The Silicon Age |title=Silicon Surfaces and Formation of Interfaces: Basic Science in the Industrial World |date=2000 |publisher=[[Company:World Scientific|World Scientific]] |isbn=978-981-02-3286-3 |pages=[https://archive.org/details/siliconsurfacesf0000dabr/page/3 3–13] |chapter-url=https://books.google.com/books?id=ZlefXcP3tQAC&pg=PA3 |url=https://archive.org/details/siliconsurfacesf0000dabr/page/3 }}</ref><ref name="Siffert">{{cite book |last1=Siffert |first1=Paul |last2=Krimmel |first2=Eberhard |chapter=Preface |title=Silicon: Evolution and Future of a Technology |date=2013 |publisher=Springer Science & Business Media |isbn=978-3-662-09897-4 |chapter-url=https://books.google.com/books?id=Qxj_CAAAQBAJ&pg=PR5}}</ref> This is due to silicon being the dominant material of the Silicon Age (also known as the Digital Age or [[Philosophy:Information Age|Information Age]]), similar to how the Stone Age, [[History:Bronze Age|Bronze Age]] and [[History:Iron Age|Iron Age]] were defined by the dominant materials during their respective [[History:Three-age system|ages of civilization]].<ref name="Feldman" />

Because silicon is an important element in high-technology semiconductor devices, many places in the world bear its name. For example, Santa Clara Valley in California acquired the nickname Silicon Valley, as the element is the base material in the [[Engineering:Semiconductor industry|semiconductor industry]] there. Since then, many other places have been similarly dubbed, including Silicon Wadi in Israel; Silicon Forest in Oregon; Silicon Hills in Austin, Texas; Silicon Slopes in Salt Lake City, Utah; [[Organization:Silicon Saxony|Silicon Saxony]] in Germany; Silicon Valley in India; Silicon Border in Mexicali, Mexico; Silicon Fen in Cambridge, England; Silicon Roundabout in London; Silicon Glen in Scotland; Silicon Gorge in Bristol, England; Silicon Alley in New York City; and Silicon Beach in Los Angeles.<ref>{{cite web |url=http://www.innovationjournalism.org/ij4/presentations/turouskalidavidnordfors.pdf |title=The role of journalism in creating the metaphor of Silicon Valley |last1=Uskali |first1=T. |last2=Nordfors |first2=D. |date=23 May 2007  |work=Innovation Journalism 4 Conference, Stanford University|access-date=2016-08-08 |url-status=dead |archive-url=https://web.archive.org/web/20120907002807/http://www.innovationjournalism.org/ij4/presentations/turouskalidavidnordfors.pdf |archive-date=2012-09-07 }}</ref>

==Characteristics==
===Physical and atomic===
[[File:Silicon-unit-cell-3D-balls.png|thumb|upright=0.8|Silicon crystallizes in a [[Chemistry:Diamond|diamond]] [[Cubic crystal system|cubic crystal structure]] by forming sp<sup>3</sup> hybrid orbitals.<ref>{{Cite web|title=Silicon and Germanium|url=http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/sili2.html|access-date=2021-06-07|website=hyperphysics.phy-astr.gsu.edu}}</ref>
]]
A silicon atom has fourteen electrons. In the ground state, they are arranged in the electron configuration [Ne]3s<sup>2</sup>3p<sup>2</sup>. Of these, four are [[Physics:Valence electron|valence electron]]s, occupying the 3s orbital and two of the 3p orbitals. Like the other members of its group, the lighter [[Chemistry:Carbon|carbon]] and the heavier [[Chemistry:Germanium|germanium]], [[Chemistry:Tin|tin]], and [[Chemistry:Lead|lead]], it has the same number of valence electrons as valence orbitals: hence, it can complete its [[Octet rule|octet]] and obtain the stable [[Chemistry:Noble gas|noble gas]] configuration of [[Chemistry:Argon|argon]] by forming sp<sup>3</sup> hybrid orbitals, forming tetrahedral {{chem|SiX|4}} derivatives where the central silicon atom shares an electron pair with each of the four atoms it is bonded to.<ref name="King0">{{harvnb|King|1995|pp=xiii–xviii}}</ref> The first four ionisation energies of silicon are 786.3, 1576.5, 3228.3, and 4354.4&nbsp;kJ/mol respectively; these figures are high enough to preclude the possibility of simple cationic chemistry for the element. Following periodic trends, its single-bond covalent radius of 117.6&nbsp;pm is intermediate between those of carbon (77.2&nbsp;pm) and germanium (122.3&nbsp;pm). The hexacoordinate ionic radius of silicon may be considered to be 40&nbsp;pm, although this must be taken as a purely notional figure given the lack of a simple {{chem|Si|4+}} cation in reality.{{sfn|Greenwood|Earnshaw|1997|pp=372}}

====Electrical====
At standard temperature and pressure, silicon is a shiny [[Physics:Semiconductor|semiconductor]] with a bluish-grey metallic lustre; as typical for semiconductors, its resistivity drops as temperature rises. This arises because silicon has a small energy gap ([[Physics:Band gap|band gap]]) between its highest occupied energy levels (the valence band) and the lowest unoccupied ones (the conduction band). The [[Physics:Fermi level|Fermi level]] is about halfway between the [[Physics:Valence and conduction bands|valence and conduction bands]] and is the energy at which a state is as likely to be occupied by an electron as not. Hence pure silicon is effectively an insulator at room temperature. However, [[Physics:Doping (semiconductor)|doping]] silicon with a [[Chemistry:Pnictogen|pnictogen]] such as [[Chemistry:Phosphorus|phosphorus]], [[Chemistry:Arsenic|arsenic]], or [[Chemistry:Antimony|antimony]] introduces one extra electron per dopant and these may then be excited into the conduction band either thermally or photolytically, creating an [[Chemistry:Extrinsic semiconductor#N-type semiconductors|n-type semiconductor]]. Similarly, doping silicon with a [[Chemistry:Boron group|group 13 element]] such as [[Chemistry:Boron|boron]], [[Chemistry:Aluminium|aluminium]], or [[Chemistry:Gallium|gallium]] results in the introduction of acceptor levels that trap electrons that may be excited from the filled valence band, creating a [[Chemistry:Extrinsic semiconductor#P-type semiconductors|p-type semiconductor]].{{sfn|Greenwood|Earnshaw|1997|p=331}} <!-- this could be moved to electronic applications --> Joining n-type silicon to p-type silicon creates a [[Physics:P–n junction|p–n junction]] with a common Fermi level; electrons flow from n to p, while holes flow from p to n, creating a voltage drop. This p–n junction thus acts as a [[Engineering:Diode|diode]] that can rectify alternating current that allows current to pass more easily one way than the other. A [[Engineering:Transistor|transistor]] is an n–p–n junction, with a thin layer of weakly p-type silicon between two n-type regions. Biasing the emitter through a small forward voltage and the collector through a large reverse voltage allows the transistor to act as a [[Engineering:Triode|triode]] amplifier.{{sfn|Greenwood|Earnshaw|1997|p=331}}

====Crystal structure====

Silicon boils at 3265&nbsp;°C: this, while high, is still lower than the temperature at which its lighter congener [[Chemistry:Carbon|carbon]] sublimes (3642&nbsp;°C) and silicon similarly has a lower heat of vaporisation than carbon, consistent with the fact that the Si–Si bond is weaker than the C–C bond.{{sfn|Greenwood|Earnshaw|1997|p=331}}

It is also possible to construct [[Chemistry:Silicene|silicene]] layers analogous to [[Physics:Graphene|graphene]].<ref name="Aufray2010" /><ref name="Lalmi2010" />

===Isotopes===
{{Main|Physics:Isotopes of silicon}}
Naturally occurring silicon is composed of three stable [[Physics:Isotope|isotope]]s, <sup>28</sup>Si (92.23%), <sup>29</sup>Si (4.67%), and <sup>30</sup>Si (3.10%).{{NUBASE2016|ref}} Out of these, only <sup>29</sup>Si is of use in NMR and EPR spectroscopy,<ref>{{cite web| url =http://www.nyu.edu/cgi-bin/cgiwrap/aj39/NMRmap.cgi|access-date =2011-10-20| title =Interactive NMR Frequency Map| author =Jerschow, Alexej|publisher =New York University}}</ref> as it is the only one with a nuclear spin (''I'' ={{sfrac|1|2}}).{{sfn|Greenwood|Earnshaw|1997|p=330}} All three are produced in Type Ia supernovae<ref>{{cite book |last1=Seitenzahl |first1=Ivo Rolf |last2=Townsley |first2=Dean M. |title=Handbook of Supernovae |chapter=Nucleosynthesis in Thermonuclear Supernovae |date=2017 |pages=1955–1978 |doi=10.1007/978-3-319-21846-5_87|arxiv=1704.00415 |bibcode=2017hsn..book.1955S |isbn=978-3-319-21845-8 |s2cid=118993185 }}</ref><ref>{{cite journal |last1=Khokhlov |first1=A. M. |last2=Oran |first2=E. S. |last3=Wheeler |first3=J. C. |title=Deflagration‐to‐Detonation Transition in Thermonuclear Supernovae |journal=The Astrophysical Journal |date=April 1997 |volume=478 |issue=2 |pages=678–688 |doi=10.1086/303815|arxiv=astro-ph/9612226 |bibcode=1997ApJ...478..678K |s2cid=53486905 }}</ref> through the [[Astronomy:Oxygen-burning process|oxygen-burning process]], with <sup>28</sup>Si being made as part of the [[Astronomy:Alpha process|alpha process]] and hence the most abundant. The fusion of <sup>28</sup>Si with alpha particles by [[Physics:Photodisintegration|photodisintegration]] rearrangement in stars is known as the [[Astronomy:Silicon-burning process|silicon-burning process]]; it is the last stage of [[Physics:Stellar nucleosynthesis|stellar nucleosynthesis]] before the rapid collapse and violent explosion of the star in question in a [[Astronomy:Type II supernova|type II supernova]].<ref name="Cameron">{{cite journal|last1=Cameron |first1=A.G.W. |year=1973 |title=Abundance of the Elements in the Solar System |url=http://pubs.giss.nasa.gov/docs/1973/1973_Cameron_1.pdf |journal=Space Science Reviews |volume=15 |issue=1 |pages=121–146 |doi=10.1007/BF00172440 |bibcode=1973SSRv...15..121C |s2cid=120201972 |url-status=dead |archive-url=https://web.archive.org/web/20111021030549/http://pubs.giss.nasa.gov/docs/1973/1973_Cameron_1.pdf |archive-date=2011-10-21 }}</ref>

Twenty [[Physics:Radioisotopes|radioisotopes]] have been characterized, the two stablest being <sup>32</sup>Si with a [[Physics:Half-life|half-life]] of about 150&nbsp;years, and <sup>31</sup>Si with a half-life of 2.62&nbsp;hours.{{NUBASE2016|ref}} All the remaining [[Physics:Radioactive decay|radioactive]] isotopes have half-lives that are less than seven seconds, and the majority of these have half-lives that are less than one tenth of a second.{{NUBASE2016|ref}} Silicon has one known [[Physics:Nuclear isomer|nuclear isomer]], <sup>34m</sup>Si, with a half-life less than 210&nbsp;nanoseconds.{{NUBASE2016|ref}} <sup>32</sup>Si undergoes low-energy [[Physics:Beta decay|beta decay]] to [[Physics:Phosphorus-32|<sup>32</sup>P]] and then stable <sup>32</sup>[[Chemistry:Sulfur|S]]. <sup>31</sup>Si may be produced by the [[Physics:Neutron activation|neutron activation]] of natural silicon and is thus useful for quantitative analysis; it can be easily detected by its characteristic beta decay to stable <sup>31</sup>[[Chemistry:Phosphorus|P]], in which the emitted electron carries up to 1.48&nbsp;[[Physics:Electronvolt|MeV]] of energy.{{sfn|Greenwood|Earnshaw|1997|p=330}}

The known isotopes of silicon range in [[Chemistry:Mass number|mass number]] from 22 to 44.{{NUBASE2016|ref}} The most common decay mode of the isotopes with mass numbers lower than the three stable isotopes is [[Physics:Inverse beta decay|inverse beta decay]], primarily forming aluminium isotopes (13 protons) as [[Physics:Decay product|decay product]]s.{{NUBASE2016|ref}} The most common decay mode for the heavier unstable isotopes is beta decay, primarily forming phosphorus isotopes (15 protons) as decay products.{{NUBASE2016|ref}}

Silicon can enter the oceans through groundwater and riverine transport. Large fluxes of groundwater input have an isotopic composition which is distinct from riverine silicon inputs. Isotopic variations in groundwater and riverine transports contribute to variations in oceanic <sup>30</sup>Si values. Currently, there are substantial differences in the isotopic values of deep water in the world's [[Earth:Oceanic basin|ocean basins]]. Between the Atlantic and Pacific oceans, there is a deep water <sup>30</sup>Si gradient of greater than 0.3 parts per thousand. <sup>30</sup>Si is most commonly associated with productivity in the oceans.<ref>{{cite journal |last1=Reynolds |first1=B. C. |title=Modeling the modern marine δ 30 Si distribution: MODELING THE MODERN MARINE δ 30 Si DISTRIBUTION |journal=Global Biogeochemical Cycles |date=June 2009 |volume=23 |issue=2 |pages=1–13 |doi=10.1029/2008GB003266|s2cid=128652214 |doi-access=free }}</ref>

==Chemistry and compounds==
{{Main|Chemistry:Silicon compounds}}

{| class="wikitable" style="float:right; margin-top:0; margin-left:1em; text-align:center; font-size:10pt; line-height:11pt; width:25%;"
|+ style="margin-bottom: 5px;" | C–X and Si–X bond energies (kJ/mol){{sfn|Greenwood|Earnshaw|1997|p=330}}
|-
! {{nowrap|X {{=}}}}
! C
! Si
! H
! F
! Cl
! Br
! I
! O–
! N<
|-
! {{nowrap|C–X}}
| 368
| 360
| 435
| 453
| 351
| 293
| 216
| ~360
| ~305
|-
! {{nowrap|Si–X}}
| 360
| 340
| 393
| 565
| 381
| 310
| 234
| 452
| 322
|}
Crystalline bulk silicon is rather inert, but becomes more reactive at high temperatures. Like its neighbour aluminium, silicon forms a thin, continuous surface layer of [[Chemistry:Silicon dioxide|silicon dioxide]] ({{chem|SiO|2}}) that protects the metal from oxidation. Thus silicon does not measurably react with the air below 900&nbsp;°C, but formation of the vitreous dioxide rapidly increases between 950&nbsp;°C and 1160&nbsp;°C and when 1400&nbsp;°C is reached, atmospheric [[Chemistry:Nitrogen|nitrogen]] also reacts to give the nitrides SiN and {{chem|Si|3|N|4}}. Silicon reacts with gaseous [[Chemistry:Sulfur|sulfur]] at 600&nbsp;°C and gaseous [[Chemistry:Phosphorus|phosphorus]] at 1000&nbsp;°C. This oxide layer nevertheless does not prevent reaction with the [[Chemistry:Halogen|halogen]]s; [[Chemistry:Fluorine|fluorine]] attacks silicon vigorously at room temperature, [[Chemistry:Chlorine|chlorine]] does so at about 300&nbsp;°C, and [[Chemistry:Bromine|bromine]] and [[Chemistry:Iodine|iodine]] at about 500&nbsp;°C. Silicon does not react with most aqueous acids, but is oxidised and complexed by [[Chemistry:Hydrofluoric acid|hydrofluoric acid]] mixtures containing either [[Chemistry:Chlorine|chlorine]] or [[Chemistry:Nitric acid|nitric acid]] to form [[Chemistry:Hexafluorosilicic acid|hexafluorosilicates]]. It readily dissolves in hot aqueous alkali to form [[Chemistry:Silicate|silicate]]s.<ref>{{Citation|last1=Stapf|first1=André|title=Wafer Cleaning, Etching, and Texturization|date=2019|url=http://link.springer.com/10.1007/978-3-662-56472-1_17|work=Handbook of Photovoltaic Silicon|pages=311–358|editor-last=Yang|editor-first=Deren|place=Berlin, Heidelberg|publisher=Springer Berlin Heidelberg|language=en|doi=10.1007/978-3-662-56472-1_17|isbn=978-3-662-56471-4|access-date=2021-03-07|last2=Gondek|first2=Christoph|last3=Kroke|first3=Edwin|last4=Roewer|first4=Gerhard|s2cid=226945433}}</ref> At high temperatures, silicon also reacts with alkyl halides; this reaction may be catalysed by [[Chemistry:Copper|copper]] to directly synthesise [[Chemistry:Organosilicon|organosilicon]] chlorides as precursors to [[Chemistry:Silicone|silicone]] polymers. Upon melting, silicon becomes extremely reactive, alloying with most metals to form [[Chemistry:Silicide|silicide]]s, and reducing most metal oxides because the heat of formation of silicon dioxide is so large. In fact, molten silicon reacts virtually with every known kind of crucible material (except its own oxide, {{chem|SiO|2}}).<ref name="Grabmaier-1982">{{Cite book |last=Grabmaier |first=J. |url=https://www.worldcat.org/oclc/840294227 |title=Silicon Chemical Etching |date=1982 |publisher=Springer Berlin Heidelberg |isbn=978-3-642-68765-5 |location=Berlin, Heidelberg |oclc=840294227}}</ref>{{Rp|page=13}} This happens due to silicon's high binding forces for the light elements and to its high dissolving power for most elements.<ref name="Grabmaier-1982" />{{Rp|page=13}} As a result, containers for liquid silicon must be made of [[Chemistry:Refractory|refractory]], unreactive materials such as [[Chemistry:Zirconium dioxide|zirconium dioxide]] or group 4, 5, and 6 borides.{{sfn|Greenwood|Earnshaw|1997|p=331}}<ref>{{harvnb|Greenwood|Earnshaw|1997|pp=331–5}}</ref>

Tetrahedral coordination is a major structural motif in silicon chemistry just as it is for carbon chemistry. However, the 3p subshell is rather more diffuse than the 2p subshell and does not hybridise so well with the 3s subshell. As a result, the chemistry of silicon and its heavier congeners shows significant differences from that of carbon,<ref name="Kaupp">{{cite journal |last=Kaupp |first=Martin |date=1 December 2006 |title=The role of radial nodes of atomic orbitals for chemical bonding and the periodic table |url=http://depa.fquim.unam.mx/amyd/archivero/LecturasobreNodosRadiales_12854.pdf |journal=Journal of Computational Chemistry |volume=28 |issue=1 |pages=320–325 |doi=10.1002/jcc.20522 |pmid=17143872 |s2cid=12677737 |access-date=14 October 2016 |doi-access=free }}</ref> and thus octahedral coordination is also significant.{{sfn|Greenwood|Earnshaw|1997|p=331}} For example, the [[Chemistry:Electronegativity|electronegativity]] of silicon (1.90) is much less than that of carbon (2.55), because the valence electrons of silicon are further from the nucleus than those of carbon and hence experience smaller electrostatic forces of attraction from the nucleus. The poor overlap of 3p orbitals also results in a much lower tendency toward [[Chemistry:Catenation|catenation]] (formation of Si–Si bonds) for silicon than for carbon, due to the concomitant weakening of the Si–Si bond compared to the C–C bond:<ref name="King43">{{harvnb|King|1995|pp=43–44}}</ref> the average Si–Si bond energy is approximately 226&nbsp;kJ/mol, compared to a value of 356&nbsp;kJ/mol for the C–C bond.{{sfn|Greenwood|Earnshaw|1997|pp=374}} This results in multiply bonded silicon compounds generally being much less stable than their carbon counterparts, an example of the [[Chemistry:Double bond rule|double bond rule]]. On the other hand, the presence of radial nodes in the 3p orbitals of silicon suggests the possibility of hypervalence, as seen in five and six-coordinate derivatives of silicon such as {{chem|SiX|5|-}} and {{chem|SiF|6|2-}}.<ref>{{cite journal
| last1   =Kaupp
| first1  =Martin
| title   =The role of radial nodes of atomic orbitals for chemical bonding and the periodic table
| journal =Journal of Computational Chemistry
| volume  =28
| issue   =1
| year    =2007
| pages   =320–325
| issn    =0192-8651
| doi     =10.1002/jcc.20522
| pmid  =17143872
| doi-access=
}}</ref><ref name="King43" /> Lastly, because of the increasing energy gap between the valence s and p orbitals as the group is descended, the divalent state grows in importance from carbon to lead, so that a few unstable divalent compounds are known for silicon; this lowering of the main oxidation state, in tandem with increasing atomic radii, results in an increase of metallic character down the group. Silicon already shows some incipient metallic behavior, particularly in the behavior of its oxide compounds and its reaction with acids as well as bases (though this takes some effort), and is hence often referred to as a [[Chemistry:Metalloid|metalloid]] rather than a nonmetal.<ref name="King43" /> Germanium shows more, and tin is generally considered a metal.{{sfn|Greenwood|Earnshaw|1997|p=328}}

Silicon shows clear differences from carbon. For example, [[Chemistry:Organic chemistry|organic chemistry]] has very few analogies with silicon chemistry, while [[Chemistry:Silicate|silicate]] minerals have a structural complexity unseen in [[Chemistry:Oxocarbon|oxocarbon]]s.{{sfn|Greenwood|Earnshaw|1997|pp=327–328}} Silicon tends to resemble germanium far more than it does carbon, and this resemblance is enhanced by the [[Chemistry:D-block contraction|d-block contraction]], resulting in the size of the germanium atom being much closer to that of the silicon atom than periodic trends would predict.{{sfn|Greenwood|Earnshaw|1997|pp=359-361}} Nevertheless, there are still some differences because of the growing importance of the divalent state in germanium compared to silicon. Additionally, the lower Ge–O bond strength compared to the [[Chemistry:Silicon–oxygen bond|Si–O bond]] strength results in the absence of "germanone" polymers that would be analogous to [[Chemistry:Silicone|silicone]] polymers.{{sfn|Greenwood|Earnshaw|1997|pp=374}}

==Occurrence==
[[File:Olivine-gem7-10a.jpg|thumb|upright|Olivine]]
Silicon is the eighth most abundant element in the universe, coming after [[Chemistry:Hydrogen|hydrogen]], [[Chemistry:Helium|helium]], [[Chemistry:Carbon|carbon]], [[Chemistry:Nitrogen|nitrogen]], [[Chemistry:Oxygen|oxygen]], [[Chemistry:Iron|iron]], and [[Chemistry:Neon|neon]]. These abundances are not replicated well on Earth due to substantial separation of the elements taking place during the formation of the [[Astronomy:Solar System|Solar System]]. Silicon makes up 27.2% of the Earth's crust by weight, second only to oxygen at 45.5%, with which it always is associated in nature. Further fractionation took place in the formation of the Earth by [[Astronomy:Planetary differentiation|planetary differentiation]]: Earth's core, which makes up 31.5% of the mass of the Earth, has approximate composition {{chem|Fe|25|Ni|2|Co|0.1|S|3}}; the [[Earth:Mantle (geology)|mantle]] makes up 68.1% of the Earth's mass and is composed mostly of denser oxides and silicates, an example being [[Chemistry:Olivine|olivine]], {{chem|(Mg,Fe)|2|SiO|4}}; while the lighter siliceous minerals such as [[Chemistry:Aluminosilicate|aluminosilicate]]s rise to the surface and form the crust, making up 0.4% of the Earth's mass.{{sfn|Greenwood|Earnshaw|1997|p=329}}<ref>{{harvnb|Greenwood|Earnshaw|1997|pp=329–330}}</ref>

The crystallisation of [[Earth:Igneous rock|igneous rock]]s from magma depends on a number of factors; among them are the chemical composition of the magma, the cooling rate, and some properties of the individual minerals to be formed, such as [[Physics:Lattice energy|lattice energy]], melting point, and complexity of their crystal structure. As magma is cooled, [[Chemistry:Olivine|olivine]] appears first, followed by [[Chemistry:Pyroxene|pyroxene]], [[Chemistry:Amphibole|amphibole]], [[Chemistry:Biotite|biotite]] mica, orthoclase feldspar, muscovite mica, [[Chemistry:Quartz|quartz]], [[Chemistry:Zeolite|zeolite]]s, and finally, hydrothermal minerals. This sequence shows a trend toward increasingly complex silicate units with cooling, and the introduction of [[Chemistry:Hydroxide|hydroxide]] and [[Chemistry:Fluoride|fluoride]] anions in addition to oxides. Many metals may substitute for silicon. After these igneous rocks undergo [[Earth:Weathering|weathering]], transport, and deposition, [[Earth:Sedimentary rock|sedimentary rock]]s like clay, shale, and sandstone are formed. [[Earth:Metamorphism|Metamorphism]] also may occur at high temperatures and pressures, creating an even vaster variety of minerals.{{sfn|Greenwood|Earnshaw|1997|p=329}}

There are four sources for silicon fluxes into the ocean: chemical weathering of continental rocks, river transport, dissolution of continental terrigenous silicates, and the reaction between submarine basalts and hydrothermal fluid which release dissolved silicon. All four of these fluxes are interconnected in the ocean's biogeochemical cycle as they all were initially formed from the weathering of Earth's crust.<ref name="The World Ocean Silica Cycle">{{cite journal |last1=Tréguer |first1=Paul J. |last2=De La Rocha |first2=Christina L. |title=The World Ocean Silica Cycle |journal=Annual Review of Marine Science |date=3 January 2013 |volume=5 |issue=1 |pages=477–501 |doi=10.1146/annurev-marine-121211-172346|pmid=22809182 }}</ref>

Approximately 300–900 megatonnes of Aeolian dust is deposited into the world's oceans each year. Of that value, 80–240 megatonnes are in the form of particulate silicon. The total amount of particulate silicon deposition into the ocean is still less than the amount of silicon influx into the ocean via riverine transportation.<ref name="Atmospheric transport of silicon">{{cite book |last1=Tegen |first1=Ina |last2=Kohfeld |first2=Karen |title=Atmospheric transport of silicon |date=2006 |publisher=Island Press |isbn=1-59726-115-7 |pages=81–91}}</ref> Aeolian inputs of particulate lithogenic silicon into the North Atlantic and Western North Pacific oceans are the result of dust settling on the oceans from the Sahara and Gobi Desert, respectively.<ref name="The World Ocean Silica Cycle" /> Riverine transports are the major source of silicon influx into the ocean in coastal regions, while silicon deposition in the open ocean is greatly influenced by the settling of Aeolian dust.<ref name="Atmospheric transport of silicon" />

==Production==
{{See|List of countries by silicon production}}
Silicon of 96–99% purity is made by [[Chemistry:Carbothermic reaction|carbothermically]] reducing [[Earth:Quartzite|quartzite]] or sand with highly pure [[Chemistry:Coke (fuel)|coke]]. The reduction is carried out in an [[Physics:Electric arc furnace|electric arc furnace]], with an excess of {{chem|SiO|2}} used to stop [[Chemistry:Silicon carbide|silicon carbide]] (SiC) from accumulating:{{sfn|Greenwood|Earnshaw|1997|p=330}}
:{{chem|SiO|2}} + 2 C → Si + 2 CO
:2 SiC + {{chem|SiO|2}} → 3 Si + 2 CO

[[File:Ferrosilicon.JPG|thumb|upright=0.9|Ferrosilicon alloy]]
This reaction, known as carbothermal reduction of silicon dioxide, usually is conducted in the presence of scrap iron with low amounts of [[Chemistry:Phosphorus|phosphorus]] and [[Chemistry:Sulfur|sulfur]], producing [[Chemistry:Ferrosilicon|ferrosilicon]].{{sfn|Greenwood|Earnshaw|1997|p=330}} Ferrosilicon, an iron-silicon alloy that contains varying ratios of elemental silicon and iron, accounts for about 80% of the world's production of elemental silicon, with China, the leading supplier of elemental silicon, providing 4.6 million [[Tonne|tonne]]s (or 2/3rds of world output) of silicon, most of it in the form of ferrosilicon. It is followed by Russia (610,000 t), Norway (330,000 t), Brazil (240,000 t), and the United States (170,000 t).<ref>{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/silicon/mcs-2011-simet.pdf |publisher=USGS |title=Silicon Commodities Report 2011 |access-date=2011-10-20}}</ref> Ferrosilicon is primarily used by the iron and steel industry (see below) with primary use as alloying addition in iron or steel and for de-oxidation of steel in integrated steel plants.{{sfn|Greenwood|Earnshaw|1997|p=330}}

Another reaction, sometimes used, is aluminothermal reduction of silicon dioxide, as follows:<ref name="Ullmann574">{{harvnb|Zulehner|Neuer|Rau|p=574}}</ref>
:3 {{chem|SiO|2}} + 4 Al → 3 Si + 2 {{chem|Al|2|O|3}}

Leaching powdered 96–97% pure silicon with water results in ~98.5% pure silicon, which is used in the chemical industry. However, even greater purity is needed for semiconductor applications, and this is produced from the reduction of tetrachlorosilane (silicon tetrachloride) or [[Chemistry:Trichlorosilane|trichlorosilane]]. The former is made by chlorinating scrap silicon and the latter is a byproduct of [[Chemistry:Silicone|silicone]] production. These compounds are volatile and hence can be purified by repeated [[Fractional distillation|fractional distillation]], followed by reduction to elemental silicon with very pure [[Chemistry:Zinc|zinc]] metal as the reducing agent. The spongy pieces of silicon thus produced are melted and then grown to form cylindrical single crystals, before being purified by zone refining. Other routes use the thermal decomposition of [[Chemistry:Silane|silane]] or tetraiodosilane ({{chem|SiI|4}}). Another process used is the reduction of sodium hexafluorosilicate, a common waste product of the phosphate fertilizer industry, by metallic [[Chemistry:Sodium|sodium]]: this is highly exothermic and hence requires no outside energy source. Hyperfine silicon is made at a higher purity than almost any other material: [[Engineering:Transistor|transistor]] production requires impurity levels in silicon crystals less than 1 part per 10<sup>10</sup>, and in special cases impurity levels below 1 part per 10<sup>12</sup> are needed and attained.{{sfn|Greenwood|Earnshaw|1997|p=330}}

Silicon nanostructures can directly be produced from silica sand using conventional metalothermic processes, or the combustion synthesis approach. Such nanostructured silicon materials can be used in various functional applications including the anode of lithium ion batteries (LIBs) or photocatalytic applications.<ref>{{cite journal |first=A.R. |last=Kamali |title=Ultra-fast shock-wave combustion synthesis of nanostructured silicon from sand with excellent Li storage performance |journal=Sustainable Energy & Fuels |volume=3 |issue= 6|pages=1396–1405  |date=2019 |doi= 10.1039/C9SE00046A|s2cid=139986478 |url=https://pubs.rsc.org/en/content/articlelanding/2019/se/c9se00046a}}</ref>

==Applications==
===Compounds===
Most silicon is used industrially without being purified, often with comparatively little processing from its natural form. More than 90% of the Earth's crust is composed of [[Chemistry:Silicate minerals|silicate minerals]], which are compounds of silicon and oxygen, often with metallic ions when negatively charged silicate anions require cations to balance the charge. Many of these have direct commercial uses, such as clays, [[Chemistry:Silica|silica]] sand, and most kinds of building stone. Thus, the vast majority of uses for silicon are as structural compounds, either as the silicate minerals or silica (crude silicon dioxide). Silicates are used in making Portland cement (made mostly of calcium silicates) which is used in building mortar and modern stucco, but more importantly, combined with silica sand, and gravel (usually containing silicate minerals such as granite), to make the [[Chemistry:Concrete|concrete]] that is the basis of most of the very largest industrial building projects of the modern world.{{sfn|Greenwood|Earnshaw|1997|p=356}}

Silica is used to make [[Chemistry:Fire brick|fire brick]], a type of ceramic. Silicate minerals are also in whiteware ceramics, an important class of products usually containing various types of fired [[Earth:Clay|clay]] minerals (natural aluminium phyllosilicates). An example is [[Chemistry:Porcelain|porcelain]], which is based on the silicate mineral [[Chemistry:Kaolinite|kaolinite]]. Traditional [[Chemistry:Glass|glass]] (silica-based [[Engineering:Soda–lime glass|soda–lime glass]]) also functions in many of the same ways, and also is used for windows and containers. In addition, specialty silica based [[Chemistry:Glass fiber|glass fiber]]s are used for [[Engineering:Optical fiber|optical fiber]], as well as to produce [[Chemistry:Fiberglass|fiberglass]] for structural support and [[Engineering:Glass wool|glass wool]] for [[Physics:Thermal insulation|thermal insulation]].

Silicones often are used in [[Physics:Waterproofing|waterproofing]] treatments, [[Engineering:Molding (process)|molding]] compounds, mold-[[Chemistry:Release agent|release agent]]s, mechanical seals, high temperature [[Physics:Lubricant|greases]] and waxes, and caulking compounds. Silicone is also sometimes used in [[Unsolved:Breast implant|breast implant]]s, contact lenses, explosives and [[Pyrotechnics|pyrotechnics]].<ref>{{cite journal |doi=10.1002/prep.200700021 |title=Special Materials in Pyrotechnics: VI. Silicon – An Old Fuel with New Perspectives |last1=Koch |first1=E.C. |last2=Clement |first2=D. |journal=Propellants, Explosives, Pyrotechnics |volume=32 |page=205 |date=2007 |issue=3}}</ref> [[Company:Silly Putty|Silly Putty]] was originally made by adding [[Chemistry:Boric acid|boric acid]] to [[Chemistry:Silicone oil|silicone oil]].<ref>{{cite book|chapter-url ={{google books |plainurl=y |id=jftapGDTmYUC|page=90}} |chapter=Silly Putty |title=Timeless toys: classic toys and the playmakers who created them |first=Tim |last=Walsh |publisher=Andrews McMeel Publishing |date=2005 |isbn=978-0-7407-5571-2}}</ref><!--Now name-brand Silly Putty also contains significant amounts of elemental silicon. (Silicon binds to the silicone and allows the material to bounce 20% higher.){{Citation needed|date=January 2008}} https://books.google.com/books?id=F2ApK7QnbPUC&pg=PA125 does not mention silicon--> Other silicon compounds function as high-technology abrasives and new high-strength ceramics based upon [[Chemistry:Silicon carbide|silicon carbide]]. Silicon is a component of some [[Chemistry:Superalloy|superalloy]]s.

===Alloys===
Elemental silicon is added to molten [[Chemistry:Cast iron|cast iron]] as [[Chemistry:Ferrosilicon|ferrosilicon]] or silicocalcium alloys to improve performance in casting thin sections and to prevent the formation of [[Chemistry:Cementite|cementite]] where exposed to outside air. The presence of elemental silicon in molten iron acts as a sink for oxygen, so that the steel carbon content, which must be kept within narrow limits for each type of steel, can be more closely controlled. Ferrosilicon production and use is a monitor of the steel industry, and although this form of elemental silicon is grossly impure, it accounts for 80% of the world's use of free silicon. Silicon is an important constituent of [[Chemistry:Electrical steel|electrical steel]], modifying its resistivity and [[Physics:Ferromagnetic|ferromagnetic]] properties.

The properties of silicon may be used to modify alloys with metals other than iron. "Metallurgical grade" silicon is silicon of 95–99% purity. About 55% of the world consumption of metallurgical purity silicon goes for production of aluminium-silicon alloys ([[Chemistry:Silumin|silumin]] alloys) for aluminium part casts, mainly for use in the {{wipe|Automotive industry}}. Silicon's importance in aluminium casting is that a significantly high amount (12%) of silicon in aluminium forms a eutectic mixture which solidifies with very little thermal contraction. This greatly reduces tearing and cracks formed from stress as casting alloys cool to solidity. Silicon also significantly improves the hardness and thus wear-resistance of aluminium.<ref name="diecasting">{{cite web|last=Apelian |first=D.|date=2009 |url=http://www.diecasting.org/research/wwr/WWR_AluminumCastAlloys.pdf |title=Aluminum Cast Alloys: Enabling Tools for Improved Performance |publisher=North American Die Casting Association |location=Wheeling, Illinois|archive-url=https://web.archive.org/web/20120106013105/http://www.diecasting.org/research/wwr/WWR_AluminumCastAlloys.pdf|archive-date=2012-01-06}}</ref><ref name="USGS" />

===Electronics===
{{Main|Engineering:Semiconductor device fabrication}}
{{Further|Engineering:Semiconductor industry}}
[[File:Silicon wafer with mirror finish.jpg|thumb|upright|Silicon wafer with mirror finish]]

Most elemental silicon produced remains as a ferrosilicon alloy, and only approximately 20% is refined to metallurgical grade purity (a total of 1.3–1.5 million metric tons/year). An estimated 15% of the world production of metallurgical grade silicon is further refined to semiconductor purity.<ref name="USGS" /> This typically is the "nine-9" or 99.9999999% purity,<ref>"Semi" SemiSource 2006: A supplement to Semiconductor International. December 2005. Reference Section: ''How to Make a Chip.'' Adapted from Design News. Reed Electronics Group.</ref> nearly defect-free single [[Chemistry:Crystalline|crystalline]] material.<ref>SemiSource 2006: A supplement to Semiconductor International. December 2005. Reference Section: ''How to Make a Chip.'' Adapted from Design News. Reed Electronics Group.</ref>

[[Earth:Monocrystalline silicon|Monocrystalline silicon]] of such purity is usually produced by the [[Physics:Czochralski process|Czochralski process]], and is used to produce [[Engineering:Wafer (electronics)|silicon wafers]] used in the [[Engineering:Semiconductor industry|semiconductor industry]], in electronics, and in some high-cost and high-efficiency photovoltaic applications.<ref name="Ullmann590">{{harvnb|Zulehner|Neuer|Rau|p=590}}</ref> Pure silicon is an [[Chemistry:Intrinsic semiconductor|intrinsic semiconductor]], which means that unlike metals, it conducts [[Physics:Electron hole|electron hole]]s and electrons released from atoms by heat; silicon's [[Physics:Electrical conductivity|electrical conductivity]] increases with higher temperatures. Pure silicon has too low a conductivity (i.e., too high a resistivity) to be used as a circuit element in electronics. In practice, pure silicon is doped with small concentrations of certain other elements, which greatly increase its conductivity and adjust its electrical response by controlling the number and charge ([[Physics:Electron hole|positive]] or [[Physics:Electron|negative]]) of activated carriers. Such control is necessary for [[Engineering:Transistor|transistor]]s, [[Physics:Solar cell|solar cell]]s, [[Physics:Semiconductor detector|semiconductor detector]]s, and other [[Physics:Semiconductor device|semiconductor device]]s used in the computer industry and other technical applications.<ref name="Ullmann573">{{harvnb|Zulehner|Neuer|Rau|p=573}}</ref> In [[Physics:Silicon photonics|silicon photonics]], silicon may be used as a continuous wave [[Physics:Raman laser|Raman laser]] medium to produce coherent light.<ref name="dekker_2008">{{cite journal |title=Ultrafast nonlinear all-optical processes in silicon-on-insulator waveguides |journal=[[Physics:Journal of Physics D|Journal of Physics D]] |year=2008 |volume=40 |issue=14 |page=R249–R271 |doi=10.1088/0022-3727/40/14/r01
|bibcode=2007JPhD...40..249D |last1=Dekker |first1=R |last2=Usechak |first2=N |last3=Först |first3=M |last4=Driessen |first4=A|s2cid=123008652 }}</ref>

In common [[Engineering:Integrated circuit|integrated circuit]]s, a wafer of monocrystalline silicon serves as a mechanical support for the circuits, which are created by doping and insulated from each other by thin layers of [[Chemistry:Silicon dioxide|silicon oxide]], an insulator that is easily produced on Si surfaces by processes of [[Physics:Thermal oxidation|thermal oxidation]] or [[Engineering:LOCOS|local oxidation (LOCOS)]], which involve exposing the element to oxygen under the proper conditions that can be predicted by the [[Physics:Deal–Grove model|Deal–Grove model]]. Silicon has become the most popular material for both high power semiconductors and integrated circuits because it can withstand the highest temperatures and greatest electrical activity without suffering avalanche breakdown (an electron avalanche is created when heat produces free electrons and holes, which in turn pass more current, which produces more heat). In addition, the insulating oxide of silicon is not soluble in water, which gives it an advantage over [[Chemistry:Germanium|germanium]] (an element with similar properties which can also be used in semiconductor devices) in certain fabrication techniques.<ref>[http://www.mpoweruk.com/semiconductors.htm Semiconductors Without the Quantum Physics]. Electropaedia</ref>

Monocrystalline silicon is expensive to produce, and is usually justified only in production of integrated circuits, where tiny crystal imperfections can interfere with tiny circuit paths. For other uses, other types of pure silicon may be employed. These include hydrogenated amorphous silicon and upgraded metallurgical-grade silicon (UMG-Si) used in the production of low-cost, large-area electronics in applications such as liquid crystal displays and of large-area, low-cost, thin-film solar cells. Such semiconductor grades of silicon are either slightly less pure or polycrystalline rather than monocrystalline, and are produced in comparable quantities as the monocrystalline silicon: 75,000 to 150,000 metric tons per year. The market for the lesser grade is growing more quickly than for monocrystalline silicon. By 2013, polycrystalline silicon production, used mostly in solar cells, was projected to reach 200,000 metric tons per year, while monocrystalline semiconductor grade silicon was expected to remain less than 50,000 tons per year.<ref name="USGS">Corathers, Lisa A. [http://minerals.usgs.gov/minerals/pubs/commodity/silicon/myb1-2009-simet.pdf 2009 Minerals Yearbook]. USGS</ref>

===Quantum dots===
Silicon quantum dots are created through the thermal processing of hydrogen [[Chemistry:Silsesquioxane|silsesquioxane]] into nanocrystals ranging from a few nanometers to a few microns, displaying size dependent [[Physics:Luminescence|luminescent]] properties.<ref>{{Cite journal|last1=Clark|first1=Rhett J.|last2=Aghajamali|first2=Maryam|last3=Gonzalez|first3=Christina M.|last4=Hadidi|first4=Lida|last5=Islam|first5=Muhammad Amirul|last6=Javadi|first6=Morteza|last7=Mobarok|first7=Md Hosnay|last8=Purkait|first8=Tapas K.|last9=Robidillo|first9=Christopher Jay T.|last10=Sinelnikov|first10=Regina|last11=Thiessen|first11=Alyxandra N.|date=2017-01-10|title=From Hydrogen Silsesquioxane to Functionalized Silicon Nanocrystals|url=https://doi.org/10.1021/acs.chemmater.6b02667|journal=Chemistry of Materials|volume=29|issue=1|pages=80–89|doi=10.1021/acs.chemmater.6b02667|issn=0897-4756}}</ref><ref>{{Cite journal|last1=Hessel|first1=Colin M.|last2=Henderson|first2=Eric J.|last3=Veinot|first3=Jonathan G. C.|date=2007|title=Hydrogen Silsesquioxane: A Molecular Precursor for Nanocrystalline Si—SiO2 Composites and Freestanding Hydride-Surface-Terminated Silicon Nanoparticles.|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/chin.200710014|journal=ChemInform|language=en|volume=38|issue=10|doi=10.1002/chin.200710014|issn=1522-2667}}</ref> The nanocrystals display large [[Physics:Stokes shift|Stokes shift]]s converting photons in the ultraviolet range to photons in the visible or infrared, depending on the particle size, allowing for applications in [[Physics:Quantum dot display|quantum dot display]]s and [[Physics:Luminescent solar concentrator|luminescent solar concentrator]]s due to their limited self absorption. A benefit of using silicon based [[Physics:Quantum dot|quantum dot]]s over [[Chemistry:Cadmium|cadmium]] or [[Chemistry:Indium|indium]] is the non-toxic, metal-free nature of silicon.<ref>{{Cite journal|last1=Lim|first1=Cheol Hong|last2=Han|first2=Jeong-Hee|last3=Cho|first3=Hae-Won|last4=Kang|first4=Mingu|date=2014|title=Studies on the Toxicity and Distribution of Indium Compounds According to Particle Size in Sprague-Dawley Rats|url=http://koreascience.or.kr/article/JAKO201416747604676.page|journal=Toxicological Research|volume=30|issue=1|pages=55–63|doi=10.5487/TR.2014.30.1.055|issn=1976-8257|pmc=4007045|pmid=24795801}}</ref><ref>{{Cite journal|date=2020-03-15|title=Cadmium-induced cytotoxicity in mouse liver cells is associated with the disruption of autophagic flux via inhibiting the fusion of autophagosomes and lysosomes|url=https://www.sciencedirect.com/science/article/abs/pii/S0378427419304126|journal=Toxicology Letters|language=en|volume=321|pages=32–43|doi=10.1016/j.toxlet.2019.12.019|issn=0378-4274|last1=Zou |first1=Hui |first2=Tao |last2=Wang |first3=Junzhao  |last3=Yuan |first4=Jian  |last4=Sun |first5=Yan |last5=Yuan|first6=Jianhong  |last6=Gu |first7=Xuezhong  |last7=Liu |first8=Jianchun  |last8=Bian |first9=Zongping  |last9=Liu|pmid=31862506|s2cid=209435190}}</ref>
Another application of silicon quantum dots is for sensing of hazardous materials. The sensors take advantage of the luminescent properties of the quantum dots through [[Physics:Quenching (fluorescence)|quenching]] of the [[Physics:Photoluminescence|photoluminescence]] in the presence of the hazardous substance.<ref>{{Cite journal|last1=Nguyen|first1=An|last2=Gonzalez|first2=Christina M|last3=Sinelnikov|first3=Regina|last4=Newman|first4=W|last5=Sun|first5=Sarah|last6=Lockwood|first6=Ross|last7=Veinot|first7=Jonathan G C|last8=Meldrum|first8=Al|date=2016-02-10|title=Detection of nitroaromatics in the solid, solution, and vapor phases using silicon quantum dot sensors|url=https://doi.org/10.1088/0957-4484/27/10/105501|journal=Nanotechnology|language=en|volume=27|issue=10|pages=105501|doi=10.1088/0957-4484/27/10/105501|pmid=26863492|bibcode=2016Nanot..27j5501N|s2cid=24292648 |issn=0957-4484}}</ref> There are many methods used for hazardous chemical sensing with a few being electron transfer, [[Biology:Förster resonance energy transfer|fluorescence resonance energy transfer]], and photocurrent generation.<ref>{{Cite journal|last1=Gonzalez|first1=Christina M.|last2=Veinot|first2=Jonathan G. C.|date=2016-06-02|title=Silicon nanocrystals for the development of sensing platforms|url=https://pubs.rsc.org/en/content/articlelanding/2016/tc/c6tc01159d|journal=Journal of Materials Chemistry C|language=en|volume=4|issue=22|pages=4836–4846|doi=10.1039/C6TC01159D|issn=2050-7534}}</ref> Electron transfer quenching occurs when the lowest unoccupied molecular orbital (LUMO) is slightly lower in energy than the conduction band of the quantum dot, allowing for the transfer of electrons between the two, preventing recombination of the holes and electrons within the nanocrystals. The effect can also be achieved in reverse with a donor molecule having its highest occupied molecular orbital (HOMO) slightly higher than a valence band edge of the quantum dot, allowing electrons to transfer between them, filling the holes and preventing recombination. Fluorescence resonance energy transfer occurs when a complex forms between the quantum dot and a quencher molecule. The complex will continue to absorb light but when the energy is converted to the ground state it does not release a photon, quenching the material. The third method uses different approach by measuring the [[Physics:Photocurrent|photocurrent]] emitted by the quantum dots instead of monitoring the photoluminescent display. If the concentration of the desired chemical increases then the photocurrent given off by the nanocrystals will change in response.<ref>{{Cite journal|last1=Yue|first1=Zhao|last2=Lisdat|first2=Fred|last3=Parak|first3=Wolfgang J.|last4=Hickey|first4=Stephen G.|last5=Tu|first5=Liping|last6=Sabir|first6=Nadeem|last7=Dorfs|first7=Dirk|last8=Bigall|first8=Nadja C.|date=2013-04-24|title=Quantum-Dot-Based Photoelectrochemical Sensors for Chemical and Biological Detection|url=https://doi.org/10.1021/am3028662|journal=ACS Applied Materials & Interfaces|volume=5|issue=8|pages=2800–2814|doi=10.1021/am3028662|pmid=23547912|issn=1944-8244}}</ref>

===Thermal energy storage===
{{excerpt|Thermal energy storage|Hot silicon technology}}

==Biological role==
[[File:20110123 185042 Diatom.jpg|upright|thumb|A diatom, enclosed in a silica cell wall]]
Although silicon is readily available in the form of [[Chemistry:Silicate|silicate]]s, very few organisms use it directly. [[Biology:Diatom|Diatom]]s, [[Biology:Radiolaria|radiolaria]], and siliceous sponges use [[Biology:Biogenic silica|biogenic silica]] as a structural material for their skeletons. Some plants accumulate silica in their tissues and require silicon for their growth, for example [[Biology:Rice|rice]]. Silicon may be taken up by plants as [[Chemistry:Orthosilicic acid|orthosilicic acid]] (also known as monosilicic acid) and transported through the [[Biology:Xylem|xylem]], where it forms amorphous complexes with components of the cell wall. This has been shown to improve cell wall strength and structural integrity in some plants, thereby reducing insect herbivory and pathogenic infections. In certain plants, silicon may also upregulate the production of volatile organic compounds and phytohormones which play a significant role in plant defense mechanisms.<ref name="Kim2002">{{cite journal |doi=10.1094/PHYTO.2002.92.10.1095 |pmid=18944220 |title=Silicon-Induced Cell Wall Fortification of Rice Leaves: A Possible Cellular Mechanism of Enhanced Host Resistance to Blast |journal=Phytopathology |volume=92| issue=10 |pages=1095–103 |year=2002 |last1=Kim |first1=Sang Gyu |last2=Kim |first2=Ki Woo |last3=Park |first3=Eun Woo |last4=Choi |first4=Doil|doi-access= }}</ref><ref name="plants" /><ref name="Leroy2019">{{cite journal |last1=Leroy |first1=Nicolas |last2=de Tombeur |first2=Felix |last3=Walgraffe |first3=Yseult |last4=Cornelis |first4=Jean-Thomas |last5=Verheggen |first5=Francois |title=Silicon and plant natural defenses against insect pests: impact on plant volatile organic compounds and cascade effects on multitrophic interactions |journal=Plants |date=23 October 2019 |volume=8 |issue=444 |page=444 |doi=10.3390/plants8110444|pmid=31652861 |pmc=6918431 |doi-access=free }}</ref> In more advanced plants, the silica [[Biology:Phytolith|phytolith]]s (opal phytoliths) are rigid microscopic bodies occurring in the cell.<ref>{{cite book |chapter=Silicon |page=856 |isbn=978-0-444-53181-0 |title=Studies in Natural Products Chemistry |volume=35 |first=Atta-ur- |last=Rahman|year=2008 }}</ref><ref name="abd">{{cite journal |last1=Exley |first1=C. |title=Silicon in life:A bioinorganic solution to bioorganic essentiality |journal=Journal of Inorganic Biochemistry |volume=69 |pages=139–144 |date=1998 |doi=10.1016/S0162-0134(97)10010-1 |issue=3}}</ref><ref name="plants">{{cite journal |last1=Epstein |first1=Emanuel |title=SILICON |journal=Annual Review of Plant Physiology and Plant Molecular Biology |volume=50 |date=1999 |pmid=15012222 |doi=10.1146/annurev.arplant.50.1.641 |pages=641–664}}</ref> 

Several horticultural crops are known to protect themselves against fungal plant pathogens with silica, to such a degree that [[Biology:Fungicide|fungicide]] application may fail unless accompanied by sufficient silicon nutrition. Silicaceous plant defense molecules activate some [[Chemistry:Phytoalexin|phytoalexin]]s, meaning some of them are signalling substances producing acquired immunity. When deprived, some plants will substitute with increased production of other defensive substances.<ref name="plants" />

Life on Earth is largely composed of [[Chemistry:Carbon|carbon]], but [[Astronomy:Astrobiology|astrobiology]] considers that [[Astronomy:Extraterrestrial life|extraterrestrial life]] may have other [[Unsolved:Hypothetical types of biochemistry|hypothetical types of biochemistry]]. Silicon is considered an alternative to carbon, as it can create complex and stable molecules with four covalent bonds, required for a [[Biology:DNA|DNA]]-analog, and it is available in large quantities.<ref>{{cite book |last= Aguilera Mochón|first= Juan Antonio|date= 2016|title= La vida no terrestre|trans-title= The non-terrestrial life|url= |language= Spanish |location= |pages=43–45|publisher= RBA|isbn=978-84-473-8665-9}}</ref> 

===Marine microbial influences ===
Diatoms use silicon in the [[Biology:Biogenic silica|biogenic silica]] (bSi) form,<ref>{{Cite journal|last1=Bidle|first1=Kay D.|last2=Manganelli|first2=Maura|last3=Azam|first3=Farooq|date=2002-12-06|title=Regulation of Oceanic Silicon and Carbon Preservation by Temperature Control on Bacteria|url=https://www.science.org/doi/10.1126/science.1076076|journal=Science|language=en|volume=298|issue=5600|pages=1980–1984|doi=10.1126/science.1076076|issn=0036-8075|pmid=12471255|bibcode=2002Sci...298.1980B|s2cid=216994}}</ref> which is taken up by the silicon transport protein (SIT) to be predominantly used in the cell wall structure as frustules.<ref>{{Cite journal|last1=Durkin|first1=Colleen A.|last2=Koester|first2=Julie A.|last3=Bender|first3=Sara J.|last4=Armbrust|first4=E. Virginia|date=2016|title=The evolution of silicon transporters in diatoms|url=|journal=Journal of Phycology|language=en|volume=52|issue=5|pages=716–731|doi=10.1111/jpy.12441|issn=1529-8817|pmc=5129515|pmid=27335204}}</ref>  Silicon enters the ocean in a dissolved form such as silicic acid or silicate.<ref name="Dugdale-2001">{{Cite journal|last1=Dugdale|first1=R. C.|last2=Wilkerson|first2=F. P.|date=2001-12-30|title=Sources and fates of silicon in the ocean: the role of diatoms in the climate and glacial cycles|journal=Scientia Marina|volume=65|issue=S2|pages=141–152|doi=10.3989/scimar.2001.65s2141|issn=1886-8134|doi-access=free}}</ref>  Since diatoms are one of the main users of these forms of silicon, they contribute greatly to the concentration of silicon throughout the ocean. Silicon forms a nutrient-like profile in the ocean due to the diatom productivity in shallow depths.<ref name="Dugdale-2001" /> Therefore, concentration of silicon is lower in the shallow ocean and higher in the deep ocean.

Diatom productivity in the upper ocean contributes to the amount of silicon exported to the lower ocean.<ref>{{Cite journal|last1=Baines|first1=Stephen B.|last2=Twining|first2=Benjamin S.|last3=Brzezinski|first3=Mark A.|last4=Krause|first4=Jeffrey W.|last5=Vogt|first5=Stefan|last6=Assael|first6=Dylan|last7=McDaniel|first7=Hannah|date=December 2012|title=Significant silicon accumulation by marine picocyanobacteria|url=https://www.nature.com/articles/ngeo1641|journal=Nature Geoscience|language=en|volume=5|issue=12|pages=886–891|doi=10.1038/ngeo1641|bibcode=2012NatGe...5..886B|issn=1752-0908}}</ref>  When diatom cells are [[Biology:Lysis|lysed]] in the upper ocean, their nutrients such as iron, zinc, and silicon, are brought to the lower ocean through a process called [[Biology:Marine snow|marine snow]]. Marine snow involves the downward transfer of particulate organic matter by vertical mixing of dissolved organic matter.<ref>{{Cite journal|last=Turner|first=Jefferson T.|date=January 2015|title=Zooplankton fecal pellets, marine snow, phytodetritus and the ocean's biological pump|url=http://dx.doi.org/10.1016/j.pocean.2014.08.005|journal=Progress in Oceanography|volume=130|pages=205–248|doi=10.1016/j.pocean.2014.08.005|bibcode=2015PrOce.130..205T|issn=0079-6611}}</ref>  It has been suggested that silicon is considered crucial to diatom productivity and as long as there is silicic acid available for diatoms to use, the diatoms can contribute to other important nutrient concentrations in the deep ocean as well.<ref>{{Cite journal|last1=Yool|first1=Andrew|last2=Tyrrell|first2=Toby|date=2003|title=Role of diatoms in regulating the ocean's silicon cycle|url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2002GB002018|journal=Global Biogeochemical Cycles|language=en|volume=17|issue=4|pages=n/a|doi=10.1029/2002GB002018|bibcode=2003GBioC..17.1103Y|s2cid=16849373|issn=1944-9224|citeseerx=10.1.1.394.3912}}</ref>

In coastal zones, diatoms serve as the major phytoplanktonic organisms and greatly contribute to biogenic silica production. In the open ocean, however, diatoms have a reduced role in global annual silica production. Diatoms in North Atlantic and North Pacific subtropical gyres only contribute about 5-7% of global annual marine silica production. The [[Earth:Southern Ocean|Southern Ocean]] produces about one-third of global marine biogenic silica.<ref name="The World Ocean Silica Cycle" /> The Southern Ocean is referred to as having a "biogeochemical divide"<ref>{{cite journal |last1=Marinov |first1=I. |last2=Gnanadesikan |first2=A. |last3=Toggweiler |first3=J. R. |last4=Sarmiento |first4=J. L. |title=The Southern Ocean biogeochemical divide |journal=Nature |date=June 2006 |volume=441 |issue=7096 |pages=964–967 |doi=10.1038/nature04883|pmid=16791191 |bibcode=2006Natur.441..964M |s2cid=4428683 }}</ref> since only minuscule amounts of silicon are transported out of this region.

===Human nutrition===
There is some evidence that silicon is important to human health for their nail, hair, bone, and skin tissues,<ref>{{cite book|first1=Keith R.|last1=Martin|chapter=Silicon: The Health Benefits of a Metalloid |editor=Astrid Sigel|editor2=Helmut Sigel|editor3=Roland K.O. Sigel|title=Interrelations between Essential Metal Ions and Human Diseases|series=Metal Ions in Life Sciences|volume=13|date=2013|publisher=Springer|pages=451–473|doi=10.1007/978-94-007-7500-8_14|pmid=24470100|isbn=978-94-007-7499-5}}</ref> for example, in studies that demonstrate that premenopausal women with higher dietary silicon intake have higher [[Physics:Bone density|bone density]], and that silicon supplementation can increase bone volume and density in patients with [[Medicine:Osteoporosis|osteoporosis]].<ref name="jugdaohsingh2007silicon">{{cite journal |last1=Jugdaohsingh |first1=R. |title=Silicon and bone health |journal=The Journal of Nutrition, Health and Aging |date=Mar–Apr 2007 |volume=11 |issue=2 |pages=99–110 |pmc=2658806 |pmid=17435952}}</ref> Silicon is needed for synthesis of [[Biology:Elastin|elastin]] and [[Biology:Collagen|collagen]], of which the aorta contains the greatest quantity in the human body,<ref name="LoeperLoeper1978">{{Cite book |last1=Loeper |first1=J. |last2=Fragny |first2=M. |title=Biochemistry of Silicon and Related Problems |chapter=The Physiological Role of the Silicon and its AntiAtheromatous Action |year=1978 |pages=281–296 |doi=10.1007/978-1-4613-4018-8_13 |isbn=978-1-4613-4020-1}}</ref> and has been considered an [[Chemistry:Mineral (nutrient)|essential element]];<ref name="Niels">{{cite journal |doi =10.1146/annurev.nu.04.070184.000321 |pages=21–41 |journal=Annual Review of Nutrition |volume=4 |date=1984 |title=Ultratrace Elements in Nutrition |first=Forrest H. |last=Nielsen |pmid=6087860}}</ref> nevertheless, it is difficult to prove its essentiality, because silicon is very common, and hence, deficiency symptoms are difficult to reproduce.<ref name="lipp">{{Cite book |publisher=University Science Books |isbn=978-0-935702-72-9 |page=411 |last=Lippard |first=Stephen J. |author2=Jeremy M. Berg |title =Principles of Bioinorganic Chemistry |year=1994 |location=Mill Valley, CA}}</ref><ref>{{cite journal |author1=Muhammad Ansar Farooq |author2=Karl-Josef Dietz |title=Silicon as Versatile Player in Plant and Human Biology: Overlooked and Poorly Understood Muhammad Ansar Farooq and Karl-J |journal=Front. Plant Sci. |date=2015 |volume=6 |issue=994 |page=994 |doi=10.3389/fpls.2015.00994 |pmid=26617630|pmc=4641902 |doi-access=free }}</ref>

Silicon is currently under consideration for elevation to the status of a "plant beneficial substance by the Association of American Plant Food Control Officials (AAPFCO)."<ref>{{cite web |title=AAPFCO Board of Directors 2006 Mid-Year Meeting |archive-url=https://web.archive.org/web/20120106010519/http://www.aapfco.org/MY06BODAgenda.pdf |url=http://www.aapfco.org/MY06BODAgenda.pdf |archive-date=6 January 2012 |publisher=Association of American Plant Food Control Officials |access-date=2011-07-18 |quote=A presentation was made for Excell Minerals to recognize Silicon as a recognized plant nutrient |url-status=dead }}</ref><ref name="presentation">{{cite web |last1=Miranda |first1=Stephen R. |last2=Barker |first2=Bruce |title=Silicon: Summary of Extraction Methods |url=https://docs.google.com/viewer?a=v&q=cache:SzfW40-2DDcJ:www.aapfco.org/AM09/LSC_Si_Methods_DC.ppt+aapfco+siicon&hl=en&gl=us&pid=bl&srcid=ADGEESj4Jo-RFFj54kb6Sun3ikgJW9DMHzRAuUS045YkFErzE5NaSA084KvIyRxJp0IVX5ktDhaPPqcYLRx2hVu6K5YVWj95h2kgvkvDLQLyrxcJXXD3tQ3P5YLJ7J5F8rRYzenxznHp&sig=AHIEtbSPNk7BtSIpiRnvNI1F-2jSLN5LYA |archive-url=https://web.archive.org/web/20121112232117/https://docs.google.com/viewer?a=v&q=cache%3ASzfW40-2DDcJ%3Awww.aapfco.org%2FAM09%2FLSC_Si_Methods_DC.ppt+aapfco+siicon&hl=en&gl=us&pid=bl&srcid=ADGEESj4Jo-RFFj54kb6Sun3ikgJW9DMHzRAuUS045YkFErzE5NaSA084KvIyRxJp0IVX5ktDhaPPqcYLRx2hVu6K5YVWj95h2kgvkvDLQLyrxcJXXD3tQ3P5YLJ7J5F8rRYzenxznHp&sig=AHIEtbSPNk7BtSIpiRnvNI1F-2jSLN5LYA |url-status=dead |archive-date=November 12, 2012 |publisher=Harsco Minerals |date=August 4, 2009 |access-date=2011-07-18 }}</ref>

==Safety==
People may be exposed to elemental silicon in the workplace by breathing it in, swallowing it, or having contact with the skin or eye. In the latter two cases, silicon poses a slight hazard as an irritant. It is hazardous if inhaled.<ref name="msds">{{cite web |url=http://www.sciencelab.com/msds.php?msdsId=9924921 |title=Material Safety Data Sheet: Silicon MSDS |author=Science Lab.com |website=sciencelab.com |access-date=11 March 2018 |archive-url=https://web.archive.org/web/20180323183044/http://www.sciencelab.com/msds.php?msdsId=9924921 |archive-date=23 March 2018 |url-status=dead }}</ref> The [[Organization:Occupational Safety and Health Administration|Occupational Safety and Health Administration]] (OSHA) has set the [[Earth:Permissible exposure limit|legal limit]] for silicon exposure in the workplace as 15&nbsp;mg/m<sup>3</sup> total exposure and 5&nbsp;mg/m<sup>3</sup> respiratory exposure over an eight-hour workday. The [[Organization:National Institute for Occupational Safety and Health|National Institute for Occupational Safety and Health]] (NIOSH) has set a [[Earth:Recommended exposure limit|recommended exposure limit]] (REL) of 10&nbsp;mg/m<sup>3</sup> total exposure and 5&nbsp;mg/m<sup>3</sup> respiratory exposure over an eight-hour workday.<ref>{{cite web |title=CDC – NIOSH Pocket Guide to Chemical Hazards – Silicon |url=https://www.cdc.gov/niosh/npg/npgd0554.html |website=www.cdc.gov |access-date=2015-11-21}}</ref> Inhalation of [[Chemistry:Crystalline|crystalline]] silica dust may lead to silicosis, an [[Medicine:Occupational lung disease|occupational lung disease]] marked by [[Medicine:Inflammation|inflammation]] and scarring in the form of [[Medicine:Nodule|nodular lesions]] in the upper lobes of the lungs.<ref name="PlantVoulvoulis2012">{{cite book |author1=Jane A. Plant |author2=Nick Voulvoulis |author3=K. Vala Ragnarsdottir |title=Pollutants, Human Health and the Environment: A Risk Based Approach |journal=Applied Geochemistry |volume=26 |url=https://books.google.com/books?id=D3JS6NXez5oC&pg=PA273 |access-date=24 August 2012 |year=2012 |publisher=John Wiley & Sons |isbn=978-0-470-74261-7 |page=273|bibcode=2011ApGC...26S.238P |doi=10.1016/j.apgeochem.2011.03.113 }}</ref>

==See also==
{{div col|colwidth=20em}}
* [[Chemistry:Amorphous silicon|Amorphous silicon]]
* [[Chemistry:Black silicon|Black silicon]]
* Covalent superconductors
* [[Chemistry:List of countries by silicon production|List of countries by silicon production]]
* [[Physics:List of silicon producers|List of silicon producers]]
* [[Earth:Monocrystalline silicon|Monocrystalline silicon]]
* [[Earth:Polycrystalline silicon|Polycrystalline silicon]]
* Printed silicon electronics
* [[Chemistry:Silicene|Silicene]]
* [[Physics:Silicon nanowire|Silicon nanowire]]
* [[Chemistry:Silicon tombac|Silicon tombac]]
* Silicon Valley
* [[Engineering:Transistor|Transistor]]
{{div col end}}

==Notes==
{{notelist}}

==References==
{{Reflist}}

==Bibliography==
* {{cite book | last1 =Clayden | first1 =Jonathan |  last2 =Greeves | first2 =Nick | last3 =Warren | first3 =Stuart | author-link3 =Stuart Warren | title =Organic Chemistry | edition =2nd | publisher =Oxford University Press | date =2012 | isbn =978-0-19-927029-3}}
* {{cite book |last=King |first=R. Bruce |date=1995 |title=Inorganic Chemistry of Main Group Elements |publisher=Wiley-VCH |isbn=978-0-471-18602-1}}
* {{Ullmann |first1=Werner |last1=Zulehner |first2=Bernd |last2=Neuer |first3=Gerhard |last3=Rau| title =Silicon | doi =10.1002/14356007.a23_721}}
* {{cite journal |first=Kamal Y. |last=Kamal |title=The Silicon Age: Trends in Semiconductor Devices Industry |journal=Journal of Engineering Science and Technology Review |volume=15 |issue=1 |pages=110–5 |date=2022 |url=http://www.jestr.org/downloads/Volume15Issue1/fulltext141512022.pdf |doi = 10.25103/jestr.151.14| s2cid = 249074588}}

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|book5=Chemical elements (sorted by number)
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==External links==
* {{Cite web|title=Silicon Video - The Periodic Table of Videos - University of Nottingham|url=https://www.periodicvideos.com/videos/014.htm|access-date=2021-06-08|website=www.periodicvideos.com}}
* {{Cite web|title=CDC - NIOSH Pocket Guide to Chemical Hazards - Silicon|url=https://www.cdc.gov/niosh/npg/npgd0554.html|access-date=2021-06-08|website=www.cdc.gov}}
* {{Cite web|title=Physical properties of Silicon (Si)|url=https://www.ioffe.ru/SVA/NSM/Semicond/Si/|access-date=2021-06-08|website=www.ioffe.ru}}
* {{cite AV media |url=https://www.youtube.com/watch?v=Gej9UZZAnQ4 |date=30 November 2022 |series=Asianometry |title=The Story of Solar-Grade Silicon }}

{{Periodic table (navbox)}}
{{Silicon compounds}}


[[Category:Chemical elements]]
[[Category:Metalloids]]
[[Category:Group IV semiconductors]]
[[Category:Pyrotechnic fuels]]
[[Category:Dietary minerals]]
[[Category:Reducing agents]]
[[Category:Native element minerals]]

{{Sourceattribution|Silicon}}