document_title: Silicon

question_text: what type of bonding is present in si

question_tokens: what type of bonding is present in si

text: Silicon

text: History

text: In 1787 Antoine Lavoisier suspected that silica might be an oxide of a fundamental chemical element,[9] but the chemical affinity of silicon for oxygen is high enough that he had no means to reduce the oxide and isolate the element.[10] After an attempt to isolate silicon in 1808, Sir Humphry Davy proposed the name "silicium" for silicon, from the Latin silex, silicis for flint, and adding the "-ium" ending because he believed it to be a metal.[11] Most other languages use transliterated forms of Davy's name, sometimes adapted to local phonology (e.g. German Silizium, Turkish silisyum). A few others use instead a calque of the Latin root (e.g. Russian кремний, from кремень "flint"; Greek πυριτιο from πυρ "fire"; Finnish pii from piikivi "flint").[12]

text: In 1811, Gay-Lussac and Thénard are thought to have prepared impure amorphous silicon, through the heating of recently isolated potassium metal with silicon tetrafluoride, but they did not purify and characterize the product, nor identify it as a new element.[13] 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 nonmetal similar to boron and carbon.[14] In 1823, Jöns Jacob Berzelius prepared amorphous silicon using approximately the same method as Gay-Lussac (reducing potassium fluorosilicate with molten potassium metal), but purifying the product to a brown powder by repeatedly washing it.[15] As a result, he is usually given credit for the element's discovery.[16][17] The same year, Berzelius became the first to prepare silicon tetrachloride; silicon tetrafluoride had already been prepared long before in 1771 by Carl Wilhelm Scheele by dissolving silica in hydrofluoric acid.[10]

text: Silicon in its more common crystalline form was not prepared until 31 years later, by Deville.[18][19] By electrolyzing a mixture of sodium chloride and aluminium chloride containing approximately 10% silicon, he was able to obtain a slightly impure allotrope of silicon in 1854.[20] Later, more cost-effective methods have been developed to isolate several allotrope forms, the most recent being silicene in 2010.[21][22] Meanwhile, research on the chemistry of silicon continued; Friedrich Wöhler discovered the first volatile hydrides of silicon, synthesising trichlorosilane in 1857 and silane itself in 1858, but a detailed investigation of the 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.[23] Similarly, the first 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 Frederick Kipping.[10]

text: Starting in the 1920s, the work of William Lawrence Bragg on X-ray crystallography successfully elucidated the compositions of the silicates, which had previously been known from analytical chemistry but had not yet been understood, together with Linus Pauling's development of crystal chemistry and Victor Goldschmidt's development of geochemistry. The middle of the 20th century saw the development of the chemistry and industrial use of siloxanes and the growing use of silicone polymers, elastomers, and resins. In the late 20th century, the complexity of the crystal chemistry of silicides was mapped, along with the solid-state chemistry of doped semiconductors.[10]

text: 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 since the element is the base material used in the semiconductor industry located there. Since then, many other locations have been nicknamed for similar reasons.[24]

text: Characteristics

text: Physical and atomic

text: A silicon atom has fourteen electrons. In the ground state, they are arranged in the electron configuration [Ne]3s23p2. Of these, four are valence electrons, occupying the 3s orbital and two of the 3p orbitals. Like the other members of its group, the lighter carbon and the heavier germanium, tin, and lead, it has the same number of valence electrons as valence orbitals: hence, it can complete its octet and obtain the stable noble gas configuration of argon by forming sp3 hybrid orbitals, forming tetrahedral SiX4 derivatives where the central silicon atom shares an electron pair with each of the four atoms it is bonded to.[25] The first four ionisation energies of silicon are 786.3, 1576.5, 3228.3, and 4354.4 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 pm is intermediate between those of carbon (77.2 pm) and germanium (122.3 pm). The hexacoordinate ionic radius of silicon may be considered to be 40 pm, although this must be taken as a purely notional figure given the lack of a simple Si4+ cation in reality.[26]

text: At standard temperature and pressure, silicon is a shiny 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 between its highest occupied energy levels (the valence band) and the lowest unoccupied ones (the conduction band). The Fermi level is about halfway between the 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 an insulator at room temperature. However, doping silicon with a pnictogen such as phosphorus, arsenic, or antimony introduces one extra electron per dopant and these may then be excited into the conduction band either thermally or photolytically, creating an n-type semiconductor. Similarly, doping silicon with a group 13 element such as boron, aluminium, and gallium results in the introduction of acceptor levels that trap electrons that may be excited from the filled valence band, creating a p-type semiconductor. Joining n-type silicon to p-type silicon creates a 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 diode that can rectify alternating current that allows current to pass more easily one way than the other. A 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 triode amplifier.[27]

text: Silicon crystallises in a giant covalent structure at standard conditions, specifically in a diamond cubic lattice. It thus has a high melting point of 1414 °C, as a lot of energy is required to break the strong covalent bonds and melt the solid. It is not known to have any allotropes at standard pressure, but several other crystal structures are known at higher pressures. The general trend is one of increasing coordination number with pressure, culminating in a hexagonal close-packed allotrope at about 40 gigapascals known as Si–VII (the standard modification being Si–I). Silicon boils at 3265 °C: this, while high, is still lower than the temperature at which its lighter congener carbon sublimes (3642 °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.[27]

text: Isotopes

text: Naturally occurring silicon is composed of three stable isotopes, 28Si (92.23%), 29Si (4.67%), and 30Si (3.10%).[28] Out of these, only 29Si is of use in NMR and EPR spectroscopy,[29] as it is the only one with a nuclear spin (I = 1/2).[30] All three are produced in stars through the oxygen-burning process, with 28Si being made as part of the alpha process and hence the most abundant. The fusion of 28Si with alpha particles by photodisintegration rearrangement in stars is known as the silicon-burning process; it is the last stage of stellar nucleosynthesis before the rapid collapse and violent explosion of the star in question in a type II supernova.[31]

text: Twenty radioisotopes have been characterized, with the two stablest being 32Si with a half-life of about 150 years, and 31Si with a half-life of 2.62 hours.[28] All of the remaining 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.[28] Silicon does not have any known nuclear isomers.[28] 32Si undergoes low-energy beta decay to 32P and then stable 32S. 31Si may be produced by the neutron activation of natural silicon and is thus useful for quantitative analysis; it can be easily detected by its characteristic beta decay to stable 31P, in which the emitted electron carries up to 1.48 MeV of energy.[30]

text: The known isotopes of silicon range in mass number from 22 to 44.[28] The most common decay mode of the isotopes with mass numbers lower than the three stable isotopes is inverse beta decay, primarily forming aluminium isotopes (13 protons) as decay products.[28] The most common decay mode for the heavier unstable isotopes is beta decay, primarily forming phosphorus isotopes (15 protons) as decay products.[28]

text: Chemistry and compounds

text:
C–X and Si–X bond energies (kJ/mol)[23]

X =
C
Si
H
F
Cl
Br
I
O–
N<

C–X
368
360
435
453
351
293
216
~360
~305

Si–X
360
340
393
565
381
310
234
452
322

text: 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 silicon dioxide (SiO2) that protects the metal from oxidation. Thus silicon does not measurably react with the air below 900 °C, but formation of the vitreous dioxide rapidly increases between 950 °C and 1160 °C and when 1400 °C is reached, atmospheric nitrogen also reacts to give the nitrides SiN and Si3N4. Silicon reacts with gaseous sulfur at 600 °C and gaseous phosphorus at 1000 °C. This oxide layer nevertheless does not prevent reaction with the halogens; fluorine attacks silicon vigorously at room temperature, chlorine does so at about 300 °C, and bromine and iodine at about 500 °C. Silicon does not react with most aqueous acids, but is oxidised and fluorinated by a mixture of concentrated nitric acid and hydrofluoric acid; it readily dissolves in hot aqueous alkali to form silicates. At high temperatures, silicon also reacts with alkyl halides; this reaction can be catalysed by copper to directly synthesise organosilicon chlorides as precursors to silicone polymers. Upon melting, silicon becomes extremely reactive, alloying with most metals to form silicides, and reducing most metal oxides because the heat of formation of silicon dioxide is so large. As a result, containers for liquid silicon must be made of refractory, unreactive materials such as zirconium dioxide or group 4, 5, and 6 borides.[27]

text:
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 as well with the 3s subshell. As a result, the chemistry of silicon and its heavier congeners shows significant differences from that of carbon,[32] and thus octahedral coordination is also significant.[27] For example, the 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 towards 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:[33] the average Si–Si bond energy is approximately 226 kJ/mol, compared to a value of 356 kJ/mol for the C–C bond.[34] This results in multiply bonded silicon compounds generally being much less stable than their carbon counterparts, an example of the double bond rule. On the other hand, the presence of 3d orbitals in the valence shell of silicon suggests the possibility of hypervalence, as seen in five- and six-coordinate derivatives of silicon such as SiX−
5 and SiF2−
6.[33] 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 behaviour, particularly in the behaviour 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 metalloid rather than a nonmetal.[33] However, metallicity does not become clear in group 14 until germanium and dominant until tin, with the growing importance of the lower +2 oxidation state.[10]

text: Silicon shows clear differences with carbon. For example, organic chemistry has very few analogies with silicon chemistry, while silicate minerals have a structural complexity unseen in oxocarbons.[10] Silicon tends to resemble germanium far more than it does carbon, and this resemblance is enhanced by the 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.[26] Nevertheless, there are still some differences because of the growing importance of the divalent state in germanium compared to silicon, that result in germanium being significantly more metallic than silicon. Additionally, the lower Ge–O bond strength compared to the Si–O bond strength results in the absence of "germanone" polymers that would be analogous to silicone polymers.[34]

text: Silicides

text: Many metal silicides are known, most of which have formulae that cannot be explained through simple appeals to valence: their bonding ranges from metallic to ionic and covalent. Some known stoichiometries are M6Si, M5Si, M4Si, M15Si4, M3Si, M5Si2, M2Si, M5Si3, M3Si2, MSi, M2Si3, MSi2, MSi3, and MSi6. They are structurally more similar to the borides than the carbides, in keeping with the diagonal relationship between boron and silicon, although the larger size of silicon than boron means that exact structural analogies are few and far between. The heats of formation of the silicides are usually similar to those of the borides and carbides of the same elements, but they usually melt at lower temperatures.[35] Silicides are known for all stable elements in groups 1–10, with the exception of beryllium: in particular, uranium and the transition metals of groups 4–10 show the widest range of stoichiometries. Except for copper, the metals in groups 11–15 do not form silicides. Most instead form eutectic mixtures, although the heaviest post-transition metals mercury, thallium, lead, and bismuth are completely immiscible with liquid silicon.[35]

text:
Silicides are usually prepared by direct reaction of the elements. For example, the alkali metals and alkaline earth metals react with silicon or silicon oxide to give silicides. Nevertheless, even with these highly electropositive elements true silicon anions are not obtainable, and most of these compounds are semiconductors. For example, the alkali metal silicides (M+)
4(E4−
4) contain pyramidal tricoordinate silicon in the Si4−
4 anion, isoeelctronic with white phosphorus, P4.[35][36] Metal-rich silicides tend to have isolated silicon atoms (e.g. Cu5Si); with increasing silicon content, catenation increases, resulting in isolated clusters of two (e.g. U3Si2) or four silicon atoms (e.g. [K+]4[Si4]4−) at first, followed by chains (e.g. CaSi), layers (e.g. CaSi2), or three-dimensional networks of silicon atoms spanning space (e.g. α-ThSi2) as the silicon content rises even higher.[35]

text: The silicides of the group 1 and 2 metals are usually more reactive than the transition metal silicides. The latter usually do not react with aqueous reagents, except for hydrofluoric acid; however, they do react with much more aggressive reagents like liquid potassium hydroxide, or gaseous fluorine or chlorine when red-hot. The pre-transition metal silicides instead readily react with water and aqueous acids, usually producing hydrogen or silanes:[35]

text: Products often vary with the stoichiometry of the silicide reactant. For example, Ca2Si is polar and non-conducting and has the anti-PbCl2 structure with single isolated silicon atoms, and reacts with water to produce calcium hydroxide, hydrated silicon dioxide, and hydrogen gas. CaSi with its zigzag chains of silicon atoms instead reacts to give silanes and polymeric SiH2, while CaSi2 with its puckered layers of silicon atoms does not react with water, but will react with dilute hydrochloric acid: the product is a yellow polymeric solid with stoichiometry Si2H2O.[35]

text: Silanes

text: Speculation on silicon hydride chemistry started from the 1830s, contemporary with the development of synthetic organic chemistry. Silane itself, as well as trichlorosilane, were first synthesised by Friedrich Wöhler and Heinrich Buff in 1857 by reacting aluminium–silicon alloys with hydrochloric acid, and characterised as SiH4 and SiHCl3 by Charles Friedel and Albert Ladenburg in 1867. Disilane (Si2H6) followed in 1902, when it was first made by Henri Moissan and Samuel Smiles by the protonolysis of magnesium silicides. Further investigation had to wait until 1916 because of the great reactivity and thermal instability of the silanes; it was then that Alfred Stock began the study of silicon hydrides in earnest with new greaseless vacuum techniques, as they were found as contaminants of his focus, the boron hydrides. The names silanes and boranes are due to him, based on analogy with the alkanes.[23][37][38] Moissan and Smiles' method of preparation of silanes and silane derivatives via protonolysis of metal silicides is still used, although the yield is lowered by the hydrolysis of the products that occurs simultaneously, and thus the preferred route today is to treat substituted silanes with hydride reducing agents such as lithium aluminium hydride in etheric solutions at low temperatures. Direct reaction of HX or RX with silicon, possibly with a catalyst such as copper, is also a viable method to produce substituted silanes.[23]

text: The silanes comprise a homologous series of silicon hydrides with the general formula SinH2n + 2. They are all strong reducing agents. Unbranched and branched trains are known up to n = 8, and the cycles Si5H10 and Si6H12 are also known. The first two, silane and disilane, are colourless gases; the heavier members of the series are volatile liquids. All silanes are very reactive and catch fire or explode spontaneously in air. They become less thermally stable with room temperature, so that only silane is indefinitely stable at room temperature, although disilane does not decompose very quickly (only 2.5% of a sample decomposes after eight months have passed).[23] They decompose to form polymeric polysilicon hydride and hydrogen gas.[39][40] As expected from the difference in atomic weight, the silanes are less volatile than the corresponding alkanes and boranes, but more volatile than the corresponding germanes. They are much more reactive than the corresponding alkanes, because the larger radius of silicon compared to carbon facilitates nucleophilic attack at the silicon, the greater polarity of the Si–H bond compared to the C–H bond, and the ability of silicon to expand its octet and hence form adducts and lower the reaction's activation energy.[23]

text: Silane pyrolysis gives polymeric species and finally elemental silicon and hydrogen; indeed ultrapure silicon is commercially produced by the pyrolysis of silane. While the thermal decomposition of alkanes starts by the breaking of a C–H or C–C bond and the formation of radical intermediates, polysilanes decompose by eliminating silenes :SiH2 or :SiHR, as the activation energy of this process (~210 kJ/mol) is much less than the Si–Si and Si–H bond energies. While pure silanes do not react with pure water or dilute acids, traces of alkali catalyse immediate hydrolysis to hydrated silicon dioxide. If the reaction is carried out in methanol, controlled solvolysis results in the products SiH2(OMe)2, SiH(OMe)3, and Si(OMe)4. The Si–H bond also adds to alkenes, a reaction which proceeds slowly and speeds up with increasing substitution of the silane involved. At 450 °C, silane participates in an addition reaction with acetone, as well as a ring-opening reaction with ethylene oxide. Direct reaction of the silanes with chlorine or bromine results in explosions at room temperature, but the reaction of silane with bromine at −80 °C is controlled and yields bromosilane and dibromosilane. The monohalosilanes may be formed by reacting silane with the appropriate hydrogen halide with an Al2X6 catalyst, or by reacting silane with a solid silver halide in a heated flow reactor:[23]

text:
Among the derivatives of silane, iodosilane (SiH3I) and potassium silanide (KSiH3) are very useful synthetic intermediates in the production of more complicated silicon-containing compounds: the latter is a colourless crystalline ionic solid containing K+ cations and SiH−
3 anions in the NaCl structure, and is made by the reduction of silane by potassium metal.[41] Additionally, the reactive hypervalent species SiH−
5 is also known.[23] With suitable organic substituents it is possible to produce stable polysilanes: they have surprisingly high electric conductivities, arising from sigma delocalisation of the electrons in the chain.[42]

text: Halides

text:
Silicon and silicon carbide readily react with all four stable halogens, forming the colourless, reactive and volatile silicon tetrahalides.[43] Silicon tetrafluoride may also be made by fluorinating the other silicon halides, and is produced by the attack of hydrofluoric acid on glass.[44] Heating two different tetrahalides together also produce a random mixture of mixed halides, which may also be produced by halogen exchange reactions. The melting and boiling points of these species usually rise with increasing atomic weight, though there are many exceptions: for example, the melting and boiling points drop as one passes from SiFBr3 through SiFClBr2 to SiFCl2Br. The shift from the hypoelectronic elements in group 13 and earlier to the group 14 elements is illustrated by the change from an infinite ionic structure in aluminium fluoride to a lattice of simple covalent silicon tetrafluoride molecules, as dictated by the lower electronegativity of aluminium than silicon, the stoichiometry (the +4 oxidation state being too high for true ionicity), and the smaller size of the silicon atom compared to the aluminium atom.[43] Silicon tetrachloride is manufactured on a huge scale as a precursor to the production of pure silicon, silicon dioxide, and some silicon esters.[43] The silicon tetrahalides hydrolyse readily in water, unlike the carbon tetrahalides, again because of the larger size of the silicon atom rendering it more open to nucleophilic attack and the ability of the silicon atom to expand its octet which carbon lacks.[44] The reaction of silicon fluoride with excess hydrofluoric acid produces the octahedral hexafluorosilicate anion SiF2−
6.[44]

text: Analogous to the silanes, halopolysilanes SinX2n + 2 are also known. While catenation in carbon compounds is maximised in the hydrogen compounds rather than the halides, the opposite is true for silicon, so that the halopolysilanes are known up to at least Si14F30, Si6Cl14, and Si4Br10. A suggested explanation for this phenomenon is the compensation for the electron loss of silicon to the more electronegative halogen atoms by pi backbonding from the filled pπ orbitals on the halogen atoms to the empty dπ orbitals on silicon: this is similar to the situation of carbon monoxide in metal carbonyl complexes and explains their stability. These halopolysilanes may be produced by comproportionation of silicon tetrahalides with elemental silicon, or by condensation of lighter halopolysilanes (trimethylammonium being a useful catalyst for this reaction).[43]

text: Silica

text: Silicon dioxide (SiO2), also known as silica, is one of the most well-studied compounds, second only to water. Twelve different crystal modifications of silica are known, the most common being α-quartz, a major constituent of many rocks such as granite and sandstone. It is also known to occur pure as rock crystal; impure forms are known as rose quartz, smoky quartz, morion, amethyst, and citrine. Some poorly crystalline forms of quartz are also known, such as chalcedony, chrysoprase, carnelian, agate, onyx, jasper, heliotrope, and flint. Other modifications of silicon dioxide are known in some other minerals such as tridymite and cristobalite, as well as the much less common coesite and stishovite. Biologically generated forms are also known as kieselguhr and diatomaceous earth. Vitreous silicon dioxide is known as tektites, and obsidian, and rarely as lechatelierite. Some synthetic forms are known as keatite and W-silica. Opals are composed of complicated crystalline aggregates of partially hydrated silicon dioxide.[45]

text:
Quartz

Sandstone

Smoky quartz

Amethyst

Citrine

Agate

Chrysoprase

Onyx

Jasper

Heliotrope

Tridymite

Cristobalite

Coesite

Lechatelierite

text: Most crystalline forms of silica are made of infinite arrangements of {SiO4} tetrahedra (with Si at the centre) connected at their corners, with each oxygen atom linked to two silicon atoms. In the thermodynamically stable room-temperature form, α-quartz, these tetrahedra are linked in intertwined helical chains with two different Si–O distances (159.7 and 161.7 pm) with a Si–O–Si angle of 144°. These helices can be either left- or right-handed, so that individual α-quartz crystals are optically active. At 537 °C, this transforms quickly and reversibly into the similar β-quartz, with a change of the Si–O–Si angle to 155° but a retention of handedness. Further heating to 867 °C results in another reversible phase transition to β-tridymite, in which some Si–O bonds are broken to allow for the arrangement of the {SiO4} tetrahedra into a more open and less dense hexagonal structure. This transition is slow and hence tridymite occurs as a metastable mineral even below this transition temperature; when cooled to about 120 °C it quickly and reversibly transforms by slight displacements of individual silicon and oxygen atoms to α-tridymite, similarly to the transition from α-quartz to β-quartz. β-tridymite slowly transforms to cubic β-cristobalite at about 1470 °C, which once again exists metastably below this transition temperature and transforms at 200–280 °C to α-cristobalite via small atomic displacements. β-cristobalite melts at 1713 °C; the freezing of silica from the melt is quite slow and vitrification, or the formation of a glass, is likely to occur instead. In vitreous silica, the {SiO4} tetrahedra remain corner-connected, but the symmetry and periodicity of the crystalline forms are lost. Because of the slow conversions between these three forms, it is possible upon rapid heating to melt β-quartz (1550 °C) or β-tridymite (1703 °C). Silica boils at approximately 2800 °C. Other high-pressure forms of silica are known, such as coesite and stishovite: these are known in nature, formed under the shock pressure of a meteorite impact and then rapidly quenched to preserve the crystal structure. Similar melting and cooling of silica occurs following lightning strikes, forming glassy lechatelierite. W-silica is an unstable low-density form involving {SiO4} tetrahedra sharing opposite edges instead of corners, forming parallel chains similarly to silicon disulfide (SiS2) and silicon diselenide (SiSe2): it quickly returns to forming amorphous silica with heat or traces of water.[45]

text: Silica is rather inert chemically. It is not attacked by any acids other than hydrofluoric acid. However, it slowly dissolves in hot concentrated alkalis, and does so rather quickly in fused metal hydroxides or carbonates to give metal silicates. Among the elements, it is attacked only by fluorine at room temperature to form silicon tetrafluoride: hydrogen and carbon also react, but require temperatures over 1000 °C to do so. Silica nevertheless reacts with many metal and metalloid oxides to form a wide variety of compounds important in the glass and ceramic industries above all, but also have many other uses: for example, sodium silicate is often used in detergents due to its buffering, saponifying, and emulsifying properties.[45]

text: Silicic acids

text: Adding water to silica drops its melting point by around 800 °C due to the breaking of the structure by replacing Si–O–Si linkages with terminating Si–OH groups. Increasing water concentration results in the formation of hydrated silica gels and colloidal silica dispersions. Many hydrates and silicic acids exist in the most dilute of aqueous solutions, but these are rather insoluble and quickly precipitate and condense and cross-link to form various polysilicic acids of variable combinations following the formula [SiOx(OH)4−2x]n, similar to the behaviour of boron, aluminium, and iron, among other elements. Hence, although some simple silicic acids have been identified in dilute solutions, such as orthosilicic acid Si(OH)4 and metasilicic acid SiO(OH)2, none of these are likely to exist in the solid state.[45]

text: Silicate minerals

text:
Typical coordination of metal cations in silicates (ionic radii in pm)[46]

CN 4
LiI
(59)
BeII (27)
AlIII (39)
SiIV (26)

CN 6
NaI (102)
MgII (72)
AlIII (54)
TiIV (61)
FeII (78)

CN 8
KI (151)
CaII (112)

CN 12
KI (164)

text: About 95% of the Earth's crustal rocks are made of silica or silicate and aluminosilicate minerals, as reflected in oxygen, silicon, and aluminium being the three most common elements in the crust (in that order).[46] Measured by mass, silicon makes up 27.7% of the Earth's crust.[47] Pure silicon crystals are very rarely found in nature, but notable exceptions are crystals as large as to 0.3 mm across found during sampling gases from the Kudriavy volcano on the island of Iturup, one of the Kuril Islands.[48][49]

text: Silicate and aluminosilicate minerals have many different structures and varying stoichiometry, but they may be classified following some general principles. Tetrahedral {SiO4} units are common to almost all these compounds, either as discrete structures, or combined into larger units by the sharing of corner oxygen atoms. These may be divided into neso-silicates (discrete {SiO4} units) sharing no oxygen atoms, soro-silicates (discrete {Si2O7} units) sharing one, cyclo-silicates (closed ring structures) and ino-silicates (continuous chain or ribbon structures) both sharing two, phyllo-silicates (continuous sheets) sharing three, and tecto-silicates (continuous three-dimensional frameworks) sharing four. The lattice of oxygen atoms that results is usually close-packed or close to it, with the charge being balanced by other cations in various different polyhedral sites according to size.[46]

text:
The orthosilicates MII
2SiO
4 (M = Be, Mg, Mn, Fe, Zn) and ZrSiO4 are neso-silicates. Be2SiO4 (phenacite) is rather unusual as both BeII and SiIV occupy tetrahedral four-coordinated sites; the other divalent cations instead occupy six-coordinated octahedral sites and often isomorphously replace each other as in olivine, (Mg,Fe,Mn)2SiO4. Zircon, ZrSiO4, demands eight-coordination of the ZrIV cations due to stoichiometry and because of their larger ionic radius (84 pm). Also significant are the garnets, [MII
3MIII
2(SiO
4)
3], in which the divalent cations (e.g. Ca, Mg, Fe) are eight-coordinated and the trivalent ones are six-coordinated (e.g. Al, Cr, Fe). Regular coordination is not always present: for example, it is not found in Ca2SiO4, which mixes six- and eight-coordinate sites for CaII. Soro-silicates, involving discrete double or triple tetrahedral units, are quite rare: metasilicates involving cyclic "[(SiO3)n]2n−" units of corner-abutting tetrahedra forming a polygonal ring are also known.[46]

text:
Chain metasilicates, {SiO2−
3}
∞, form by the corner-sharing of an indefinite chain of linked {SiO4} tetrahedra. Many differences arise due to the differing repeat distances of conformation across the line of tetrahedra. A repeat distance of two is most common, as in most pyroxene minerals, but repeat distances of one, three, four, five, six, seven, nine, and twelve are also known. These chains can then link across each other to form double chains and ribbons, as in the asbestos minerals, involving repeated chains of cyclic tetrahedron rings.[46]

text:
Layer silicates, such as the clay minerals and the micas, are very common, and are often formed by horizontal cross-linking of metasilicate chains or planar condensation of smaller units. An example is kaolinite [Al2(OH)4Si2O5]; in many of these minerals cation and anion replacement is common, so that for example tetrahedral SiIV may be replaced by AlIII, octahedral AlIII by MgII, and OH− by F−. Three-dimensional framework aluminosilicates are structurally very complex; they may be conceived of as starting from the SiO2 structure, but having replaced up to one-half of the SiIV atoms with AlIII they require more cations to be included in the structure to balance charge. Examples include feldspars (the most abundant minerals on the Earth), zeolites, and ultramarines. Many feldspars can be thought of as forming part of the ternary system NaAlSi3O8–KAlSi3O8–CaAl2Si2O8. Their lattice is destroyed by high pressure prompting AlIII to undergo six-coordination rather than four-coordination, and this reaction destroying feldspars may be a reason for the Mohorovičić discontinuity, which would imply that the crust and mantle have the same chemical composition but different lattices, although this is not a universally held view. Zeolites have many polyhedral cavities in their frameworks (truncated cuboctahedra being most common, but other polyhedra are also known as zeolite cavities), allowing them to include loosely bound molecules such as water in their structure. Ultramarines alternate silicon and aluminium atoms and include a variety of other anions such as Cl−, SO2−
4, and S2−
2, but are otherwise similar to the feldspars.[46]

text: Other inorganic compounds

text: Silicon disulfide (SiS2) is formed by burning silicon in gaseous sulfur at 100 °C; sublimation of the resulting compound in nitrogen results in white, flexible long fibres reminiscent of asbestos with a structure similar to W-silica. This melts at 1090 °C and sublimes at 1250 °C; at high temperature and pressure this transforms to a crystal structure analogous to cristobalite. However, SiS2 lacks the variety of structures of SiO2, and quickly hydrolyses to silica and hydrogen sulfide. It is also ammonoloysed quickly and completely by liquid ammonia as follows to form an imide:[50]

text: It reacts with the sulfides of sodium, magnesium, aluminium, and iron to form metal thiosilicates: reaction with ethanol results in ethylsilicate Si(OEt)4 and hydrogen sulfide. Ethylsilicate is useful as its controlled hydrolysis produces adhesive or film-like forms of silica. Reacting hydrogen sulfide with silicon tetrahalides yields silicon thiohalides such as S(SiCl)3, cyclic Cl2Si(μ-S)2SiCl2, and crystalline (SiSCl2)4. Despite the double bond rule, stable organosilanethiones RR'Si=S have been made thanks to the stabilising mechanism of intermolecular coordination via an amine group.[50]

text: Silicon nitride, Si3N4, can be formed by directly reacting silicon with nitrogen above 1300 °C, but a more economical means of production is by heating silica and coke in a stream of nitrogen and hydrogen gas at 1500 °C. It would make a promising ceramic if not for the difficulty of working with and sintering it: it is chemically near-totally inert, and even above 1000 °C it keeps its strength, shape, and continues to be resistant to wear and corrosion. It is very hard (9 on the Mohs hardness scale), dissociates only at 1900 °C at 1 atm, and is quite dense (density 3.185 g/cm3), because of its compact structure similar to that of phenacite (Be2SiO4). A similar refractory material is Si2N2O, formed by heating silicon and silica at 1450 °C in an argon stream containing 5% nitrogen gas, involving 4-coordinate silicon and 3-coordinate nitrogen alternating in puckered hexagonal tilings interlinked by non-linear Si–O–Si linkages to each other.[50]

text: Reacting silyl halides with ammonia or alkylammonia derivatives in the gaseous phase or in ethanolic solution produces various volatile silylamides, which are silicon analogues of the amines:[50]

text: Many such compounds have been prepared, the only known restriction being that the nitrogen is always tertiary, and species containing the SiH–NH group are unstable at room temperature. The stoichiometry around the nitrogen atom in compounds such as N(SiH3)3is planar, which has been attributed to a pπ–dπ interaction between a lone pair on nitrogen and an empty dπ orbital on silicon. Similarly, trisilylamines are weaker as ligands than their carbon analogues, the tertiary amines, although substitution of some SiH3 groups by CH3 groups mitigates this weakness. Thus, for example, N(SiH3)3 does not form an adduct with BH3 at all, while MeN(SiH3)2 and Me2NSiH3 form adducts at low temperatures that decompose upon warming. Some silicon analogues of imines, with a Si=N double bond, are known: the first found was But2Si=N–SiBut3, which was discovered in 1986.[50]

text: Silicon carbide (SiC) was first made by Edward Goodrich Acheson in 1891, who named it carborundum to reference its intermediate hardness and abrasive power between diamond (an allotrope of carbon) and corundum (aluminium oxide). He soon founded a company to manufacture it, and today about one million tonnes are produced each year.[51] Silicon carbide exists in about 250 crystalline forms.[52] The polymorphism of SiC is characterized by a large family of similar crystalline structures called polytypes. They are variations of the same chemical compound that are identical in two dimensions and differ in the third. Thus, they can be viewed as layers stacked in a certain sequence.[53] It is made industrially by reduction of quartz sand with excess coke or anthracite at 2000–2500 °C in an electric furnace:[51]

text: It is the most thermally stable binary silicon compound, only decomposing through loss of silicon starting from around 2700 °C. It is resistant to most aqueous acids, phosphoric acid being an exception. It forms a protective layer of silicon dioxide on the surface and hence only oxidises appreciably in air above 1000 °C; removal of this layer by molten hydroxides or carbonates leads to quick oxidation. Silicon carbide is rapidly attacked by chlorine gas, which forms SiCl4 and carbon at 100 °C and SiCl4 and CCl4 at 1000 °C. It is mostly used as an abrasive and a refractory materia, as it is chemically stable and very strong, and it fractures to form a very sharp cutting edge. It is also useful as an intrinsic semiconductor, as well as an extrinsic semiconductor upon being doped.[51] In its diamond-like behaviour it serves as an illustration of the chemical similarity between carbon and silicon.[54]

text: Organosilicon compounds

text: Because the Si–C bond is close in strength to the C–C bond, organosilicon compounds tend to be markedly thermally and chemically stable. For example, tetraphenylsilane (SiPh4) may be distilled in air even at its boiling point of 428 °C, and so can its substituted derivatives Ph3SiCl and Ph2SiCl2, which boil at 378 °C and 305 °C respectively. Furthermore, since carbon and silicon are chemical congeners, organosilicon chemistry shows some significant similarities with carbon chemistry, for example in the propensity of such compounds for catenation and forming multiple bonds.[54] However, significant differences also arise: since silicon is more electropositive than carbon, bonds to more electronegative elements are generally stronger with silicon than with carbon, and vice versa. Thus the Si–F bond is significantly stronger than even the C–F bond and is one of the strongest single bonds, while the Si–H bond is much weaker than the C–H bond and is readily broken. Furthermore, the ability of silicon to expand its octet is not shared by carbon, and hence some organosilicon reactions have no organic analogues. For example, nucleophilic attack on silicon does not proceed by the SN2 or SN1 processes, but instead goes through a negatively charged true pentacoordinate intermediate and appears like a substitution at a hindered tertiary atom. This works for silicon, unlike for carbon, because the long Si–C bonds reduce the steric hindrance and the d-orbital of silicon is geometrically unconstrained for nucleophilic attack, unlike for example a C–O σ* antibonding orbital. Nevertheless, despite these differences, the mechanism is still often called "SN2 at silicon" for simplicity.[55]

text: One of the most useful silicon-containing groups is trimethylsilyl, Me3Si–. The Si–C bond connecting it to the rest of the molecule is reasonably strong, allowing it to remain while the rest of the molecule undergoes reactions, but is not so strong that it cannot be removed specifically when needed, for example by the fluoride ion, which is a very weak nucleophile for carbon compounds but a very strong one for organosilicon compounds. It may be compared to acidic protons; while trisilylmethyl is removed by hard nucleophiles instead of bases, both removals usually promote elimination. As a general rule, while saturated carbon is best attacked by nucleophiles that are neutral compounds, those based on nonmetals far down on the periodic table (e.g. sulfur, selenium, or iodine), or even both, silicon is best attacked by charged nucleophiles, particularly those involving such highly electronegative nonmetals as oxygen, fluorine, or chlorine. For example, enolates react at the carbon in haloalkanes, but at the oxygen in silyl chlorides; and when trimethylsilyl is removed from an organic molecule using hydroxide as a nucleophile, the product of the reaction is not the silanol as one would expect from using carbon chemistry as an analogy, because the siloxide is strongly nucleophilic and attacks the original molecule to yield the silyl ether hexamethyldisiloxane, (Me3Si)2O. Conversely, while the SN2 reaction is mostly unaffected by the presence of a partial positive charge (δ+) at the carbon, the analogous "SN2" reaction at silicon is so affected. Thus, for example, the silyl triflates are so electrophilic that they react 108 to 109 times faster than silyl chlorides with oxygen-containing nucleophiles. Trimethylsilyl triflate is in particular a very good Lewis acid and is used to convert carbonyl compounds to acetals and silyl enol ethers, reacting them together analogously to the aldol reaction.[55]

text: Si–C bonds are commonly formed in three ways. In the laboratory, preparation is often carried out in small quantities by reacting tetrachlorosilane with organolithium, Grignard, or organoaluminium reagents, or by catalytic addition of Si–H across C=C double bonds. The second route has the drawback of not being applicable to the most important silanes, the methyl and phenyl silanes. Organosilanes are made industrially by directly reacting alkyl or aryl halides with silicon with 10% by weight metallic copper as a catalyst. Standard organic reactions suffice to produce many derivatives; the resulting organosilanes are often significantly more reactive than their carbon congeners, readily undergoing hydrolysis, ammonolysis, alcoholysis, and condensation to form cyclic oligomers or linear polymers.[54]

text: Silicone polymers

text: The word "silicone" was first used by Frederick Kipping in 1901. He invented the word to illustrate the similarity of chemical formulae between Ph2SiO and benzophenone, Ph2CO, although he also stressed the lack of chemical resemblance due to the polymeric structure of Ph2SiO, which is not shared by Ph2CO.[54]

text: Silicones may be considered analogous to mineral silicates, in which the methyl groups of the silicones correspond to the isoelectronic O− of the silicates.[54] They are quite stable to extreme temperatures, oxidation, and water, and have useful dielectric, antistick, and antifoam properties. Furthermore, they are resistant over long periods of time to ultraviolet radiation and weathering, and are inert physiologically. They are fairly unreactive, but do react with concentrated solutions bearing the hydroxide ion and fluorinating agents, and occasionally can be even used as mild reagents for selective syntheses. For example, (Me3Si)2O is valuable for the preparation of derivatives of molybdenum and tungsten oxyhalides, converting a tungsten hexachloride suspension in dichloroethane solution quantitatively to WOCl4 in under an hour at room temperature, and then to yellow WO2Cl2 at 100 °C in light petroleum at a yield of 95% overnight.[54]

text: Occurrence

text: In the universe, silicon is the seventh most abundant element, coming after hydrogen, helium, carbon, nitrogen, oxygen, and neon. These abundances are not replicated well on Earth due to substantial separation of the elements taking place during the formation of the Solar System. Silicon makes up 27.2% of the Earth's crust by weight, second only to oxygen at 45.5%, with which it is always associated in nature. Further fractionation took place in the formation of the Earth by planetary differentiation: Earth's core, which makes up 31.5% of the mass of the Earth, has approximate composition Fe25Ni2Co0.1S3; the mantle makes up 68.1% of the Earth's mass and is composed mostly of denser oxides and silicates, an example being olivine, (Mg,Fe)2SiO4; while the lighter siliceous minerals rise to the surface and form the crust, making up 0.4% of the Earth's mass.[56]

text: The crystallisation of igneous rocks 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 lattice energy, melting point, and complexity of their crystal structure. As magma is cooled, olivine appears first, followed by pyroxene, amphibole, biotite mica, orthoclase feldspar, muscovite mica, quartz, zeolites, and finally hydrothermal minerals. This sequence shows a trend towards increasingly complex silicate units with cooling, and the introduction of hydroxide and fluoride anions in addition to oxides. Many metals can substitute for silicon. After these igneous rocks undergo weathering, transport, and deposition, sedimentary rocks like clay, shale, and sandstone are formed. Metamorphism also can occur at high temperatures and pressures, creating an even vaster variety of minerals.[56]

text: Production

text: Silicon of 96–99% purity is made by reducing quartzite or sand with highly pure coke. The reduction is carried out in an electric arc furnace, with an excess of SiO2 used to stop silicon carbide from accumulating:[30]

text: This reaction, known as carbothermal reduction of silicon dioxide, is usually conducted in the presence of scrap iron with low amounts of phosphorus and sulfur, produing ferrosilicon.[30] 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 tonnes (or 2/3 of the world output) of silicon, most of which is 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).[57] 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.[30] Another sometimes used reaction is aluminothermal reduction of silicon dioxide, as follows:[58]

text: 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 or trichlorosilane. The former is made by chlorinating scrap silicon and the latter is a byproduct of silicone production. These compounds are volatile and hence can be purified by repeated fractional distillation, followed by reduction to elemental silicon with very pure 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 silane or tetraiodosilane. Another process used is the reduction of sodium hexafluorosilicate, a common waste product of the phosphate fertiliser industry, by metallic sodium: this is highly exothermic and hence requires no outside fuel source. Hyperfine silicon is made at a higher purity than almost every other material: transistor production requires impurity levels in silicon crystals less than 1 part per 1010, and in special cases impurity levels below 1 part per 1012 are needed and attained.[30]

text: Applications

text: Compounds

text: Most silicon is used industrially without being purified, and indeed often with comparatively little processing from its natural form. Over 90% of the Earth's crust is composed of 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, 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 like granite), to make the concrete that is the basis of most of the very largest industrial building projects of the modern world.[59]

text: Silica is used to make fire brick, a type of ceramic. Silicate minerals are also in whiteware ceramics, an important class of products usually containing various types of fired clay minerals (natural aluminium phyllosilicates). An example is porcelain which is based on the silicate mineral kaolinite. Traditional glass (silica-based soda-lime glass) also functions in many of the same ways, and is also used for windows and containers. In addition, specialty silica based glass fibers are used for optical fiber, as well as to produce fiberglass for structural support and glass wool for thermal insulation.

text: Silicones are often used in waterproofing treatments, molding compounds, mold-release agents, mechanical seals, high temperature greases and waxes, and caulking compounds. Silicone is also sometimes used in breast implants, contact lenses, explosives and pyrotechnics.[60] Silly Putty was originally made by adding boric acid to silicone oil.[61] Other silicon compounds function as high-technology abrasives and new high-strength ceramics based upon silicon carbide. Silicon is a component of some superalloys.

text: Alloys

text: Elemental silicon is added to molten cast iron as ferrosilicon or silicocalcium alloys to improve performance in casting thin sections and to prevent the formation of 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 electrical steel, modifying its resistivity and ferromagnetic properties.

text: The properties of silicon can 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 (silumin alloys) for aluminium part casts, mainly for use in the 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.[62][63]

text: Electronics

text: Most elemental silicon produced remains as a ferrosilicon alloy, and only about 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.[63]

text: Pure monocrystalline silicon, which is usually produced by the Czochralski process, is used to produce silicon wafers used in the semiconductor industry, in electronics, and in some high-cost and high-efficiency photovoltaic applications.[64] Pure silicon is an intrinsic semiconductor, which means that unlike metals, it conducts electron holes and electrons released from atoms by heat; silicon's 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 (positive or negative) of activated carriers. Such control is necessary for transistors, solar cells, semiconductor detectors, and other semiconductor devices used in the computer industry and other technical applications.[65] In silicon photonics, silicon can be used as a continuous wave Raman laser medium to produce coherent light.[66]

text: In common integrated circuits, 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 silicon oxide, an insulator that is easily produced by exposing the element to oxygen under the proper conditions. 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 germanium (an element with similar properties which can also be used in semiconductor devices) in certain fabrication techniques.[67]

text: 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 quatities 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/year.[63]

text: Biological role

text: Although silicon is readily available in the form of silicates, very few organisms use it directly. Diatoms, radiolaria and siliceous sponges use biogenic silica as a structural material for skeletons. In more advanced plants, the silica phytoliths (opal phytoliths) are rigid microscopic bodies occurring in the cell; some plants, for example rice, need silicon for their growth.[68][69][70] There is some evidence that silicon is important to nail, hair, bone and skin health in humans,[71] for example in studies that show that premenopausal women with higher dietary silicon intake have higher bone density, and that silicon supplementation can increase bone volume and density in patients with osteoporosis.[72] Silicon is needed for synthesis of elastin and collagen, of which the aorta contains the greatest quantity in the human body[73] and has been considered an essential element;[74] nevertheless, it is difficult to prove its essentiality, because silicon is very common and hence deficiency symptoms are difficult to reproduce.[75]

text: 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)."[76][77] Silicon has been shown to improve plant cell wall strength and structural integrity in some plants.[78]

text: Safety

text: People can be exposed to elemental silicon in the workplace by breathing it in, swallowing it, skin contact, and eye contact. In the latter two cases, silicon poses a slight hazard as an irritant; it is hazardous if inhaled.[79] The Occupational Safety and Health Administration (OSHA) has set the legal limit (Permissible exposure limit) for silicon exposure in the workplace as 15 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a Recommended exposure limit (REL) of 10 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday.[80] Inhalation of crystalline silica dust may lead to silicosis, an occupational lung disease marked by inflammation and scarring in the form of nodular lesions in the upper lobes of the lungs.[81]


document_title: Judgement of Paris

question_text: who did paris say was the most beautiful goddess

root

text: Judgement of Paris

text: Sources of the episode[edit]

text: As with many mythological tales, details vary depending on the source. The brief allusion to the Judgement in the Iliad (24.25–30) shows that the episode initiating all the subsequent action was already familiar to its audience; a fuller version was told in the Cypria, a lost work of the Epic Cycle, of which only fragments (and a reliable summary[1]) remain. The later writers Ovid (Heroides 16.71ff, 149–152 and 5.35f), Lucian (Dialogues of the Gods 20), Pseudo-Apollodorus (Bibliotheca, E.3.2) and Hyginus (Fabulae 92), retell the story with skeptical, ironic or popularizing agendas. It appeared wordlessly on the ivory and gold votive chest of the 7th-century BC tyrant Cypselus at Olympia, which was described by Pausanias as showing:

tag: p

text: The subject was favoured by painters of red-figure pottery as early as the sixth century BC,[3] and remained popular in Greek and Roman art, before enjoying a significant revival, as an opportunity to show three female nudes, in the Renaissance.

text: Mythic narrative[edit]

text: It is recounted[4] that Zeus held a banquet in celebration of the marriage of Peleus and Thetis (parents of Achilles).  However, Eris, goddess of discord was not invited, for it was believed she would have made the party unpleasant for everyone.  Angered by this snub, Eris arrived at the celebration with a golden apple from the Garden of the Hesperides, which she threw into the proceedings as a prize of beauty.[5] According to some later versions, upon the apple was the inscription καλλίστῃ (kallistēi, "To/for the fairest one").[6]

text: Three goddesses claimed the apple: Hera, Athena and Aphrodite. They asked Zeus to judge which of them was fairest, and eventually he, reluctant to favor any claim himself, declared that Paris, a Trojan mortal, would judge their cases, for he had recently shown his exemplary fairness in a contest in which Ares in bull form had bested Paris's own prize bull, and the shepherd-prince had unhesitatingly awarded the prize to the god.[7]

text: Thus it happened that, with Hermes as their guide, the three candidates bathed in the spring of Ida, then confronted Paris on Mount Ida in the climactic moment that is the crux of the tale. After failing to judge their beauty with their clothing on, the three goddesses stripped nude to convince Paris of their worthiness. While Paris inspected them, each attempted with her powers to bribe him; Hera offered to make him king of Europe and Asia, Athena offered wisdom and skill in war, and Aphrodite, who had the Charites and the Horai to enhance her charms with flowers and song (according to a fragment of the Cypria quoted by Athenagoras of Athens), offered the world's most beautiful woman (Euripides, Andromache, l.284, Helena l. 676). This was Helen of Sparta, wife of the Greek king Menelaus. Paris accepted Aphrodite's gift and awarded the apple to her, receiving Helen as well as the enmity of the Greeks and especially of Hera. The Greeks' expedition to retrieve Helen from Paris in Troy is the mythological basis of the Trojan War.

text: The story of the Judgement of Paris naturally offered artists the opportunity to depict a sort of beauty contest between three beautiful female nudes, but the myth, at least since Euripides, rather concerns a choice among the gifts that each goddess embodies. The bribery involved is ironic and a late ingredient.

text: According to a tradition suggested by Alfred J. Van Windekens,[8] objectively, "cow-eyed" Hera was indeed the most beautiful, not Aphrodite. However, Hera was the goddess of the marital order and of cuckolded wives, amongst other things.  She was often portrayed as the shrewish, jealous wife of Zeus, who himself often escaped from her controlling ways by cheating on her with other women, mortal and immortal. She had fidelity and chastity in mind and was careful to be modest when Paris was inspecting her. Aphrodite, though not as objectively beautiful as Hera, was the goddess of sexuality, and was effortlessly more sexual and charming before him. Thus, she was able to sway Paris into judging her the fairest. Athena's beauty is rarely commented in the myths, perhaps because Greeks held her up as an asexual being, being able to "overcome" her "womanly weaknesses"  to become both wise and talented in war (both considered male domains by the Greeks). Her rage at losing makes her join the Greeks in the battle against Paris' Trojans, a key event in the turning point of the war.

text: In post-Classical art[edit]

text: The subject became popular in art from the late Middle Ages onwards. All three goddesses were usually shown nude, though in ancient art only Aphrodite is ever unclothed, and not always.[9] The opportunity for three female nudes was a large part of the attraction of the subject.  It appeared in illuminated manuscripts and was popular in decorative art, including 15th-century Italian inkstands and other works in maiolica, and cassoni.[10]  As a subject for easel paintings, it was more common in Northern Europe, although Marcantonio Raimondi's engraving of c. 1515, probably based on a drawing by Raphael, and using a composition derived from a Roman sarcophagus, was a highly influential treatment, which made Paris's Phrygian cap an attribute in most later versions.[11]

text: The subject was painted many (supposedly 23) times by Lucas Cranach the Elder, and was especially attractive to Northern Mannerist painters.  Rubens painted  several compositions of the subject at different points in his career. Watteau and Angelica Kauffman were among the artists who painted the subject in the 18th century. The Judgement of Paris was painted frequently by academic artists of the 19th century, and less often by their more progressive contemporaries such as Renoir and Cézanne. Later artists who have painted the subject include André Lhote, Enrique Simonet (El Juicio de Paris 1904) and Salvador Dalí.

text: Ivo Saliger (1939), Adolf Ziegler (1939) and Joseph Thorak (1941) also used the classic myth to propagate German renewal during the Nazi period.[citation needed]

text: Gallery[edit]

text: Paintings[edit]

text:
Miniature, c. 1495

Lucas Cranach the Elder, c. between 1512-1514

Niklaus Manuel, c. 1520

Lucas Cranach the Elder, c. 1528

Lucas Cranach the Elder, c. 1530

Joan de Joanes, c. approx. 1523-1579

Frans Floris, c. 1548

Frans Floris, c. 1550s

Hendrick De Clerck, 1560-1630, The Phoebus Foundation

Hans von Aachen, c. 1588

Hans von Aachen, c. 1593.

Hendrick van Balen the Elder, c. 1599

Joachim Wtewael, c. 1605

Peter Paul Rubens, c. 1606

Peter Paul Rubens, c. 1625

Anthony van Dyck, c.1628

Peter Paul Rubens, c. 1638-1639

Cornelis Cornelisz. van Haarlem, c. 1628

Claude Lorrain, c. 1645-1646

Carel van Savoyen, c. 1650-1660

Luca Giordano, c. between 1681-1683

Adriaen van der Werff, c. 1712

Adriaen van der Werff, c. 1716

Michele Rocca, c. between 1710-1720

Antoine Watteau, c. 1720

Anton Raphael Mengs, c. 1757

Angelica Kauffman, c. 1770-1797

François-Xavier Fabre, c. 1808

Guillaume Guillon Lethière, c. 1812

Joseph Hauber, c. 1819

Jean-Baptiste Regnault, c. 1820

Henri-Pierre Picou, c. between 1824-1895

Paul Cézanne, c. 1862-1864

Anselm Feuerbach, c. 1869-1870

Max Klinger, c. 1886-1887

El Juicio de Paris by Enrique Simonet, c. 1904 (Museo de Málaga)

Eduard Lebiedzki, c. by 1906

Eduard Veith, c. by 1925

tag: ul

text: Mosaïc[edit]

text:
Unknown, 115–150 AD, Louvre Museum (Ma 3443)

Unknown, 115–150 AD, detail, Louvre Museum (Ma 3443)

text: Sculptures and engravings[edit]

text:
An Etruscan bronze mirrorback, 4th-3rd century BCE (Louvre)

Marcantonio Raimondi after Raphael, c. 1510-20

Dorman Hering, c. 1529

Willem Isaacsz van Swanenburg, c. 1609

Capodimonte porcelain, Capitoline Museums, Rome

Landolin Ohmacht, 1804-07

text: Kallistēi[edit]

text: Kallistēi  is the word of the Ancient Greek language inscribed on the Golden Apple of Discord by Eris.  In Greek, the word is καλλίστῃ (the dative singular of the feminine superlative of καλος, beautiful).  Its meaning can be rendered "to the fairest one".

text: Calliste (Καλλίστη; Mod. Gk. Kallisti) is also an ancient name for the isle of Thera.

text: Use in Discordianism[edit]

text: The word Kallisti (Modern Greek) written on a golden apple, has become a principal symbol of Discordianism, a post-modernist religion.  In non-philological texts (such as Discordian ones) the word is usually spelled as καλλιστι. Most versions of Principia Discordia actually spell it as καλλιχτι, but this is definitely incorrect; in the afterword of the 1979 Loompanics edition of Principia, Gregory Hill says that was because on the IBM typewriter he used, not all Greek letters coincided with Latin ones, and he didn't know enough of the letters to spot the mistake. Zeus' failure to invite Eris is referred to as The Original Snub in Discordian mythology.[12]

text: Dramatizations[edit]

text: The story is the basis of an opera,  The Judgement of Paris, with a libretto by William Congreve, that was set to music by four composers in London, 1700–1701. Thomas Arne composed a highly successful score to the same libretto in 1742. The opera Le Cinesi (The Chinese Women) by Christoph Willibald Gluck (1754) concludes with a ballet, The Judgement of Paris, sung as a vocal quartet. Francesco Cilea's 1902 opera Adriana Lecouvreur also includes a Judgement of Paris ballet sequence.

text: The story is the basis of an earlier opera, Il pomo d'oro, in a prologue and five acts by the Italian composer Antonio Cesti with a libretto by Francesco Sbarra (1611-1668). It was first performed before the imperial court in a specially constructed open-air theatre Vienna in 1668. The work was so long it had to be staged over the course of two days: the Prologue, Acts One and Two were given on July 12; Acts Three, Four and Five on July 14. The staging was unprecedented for its magnificence (and expense). The designer Ludovico Ottavio Burnacini provided no fewer than 24 sets and there were plenty of opportunities for spectacular stage machinery, including shipwrecks and collapsing towers.

text: Novelist Gore Vidal named his 1952 book, The Judgment of Paris, after this story.

text: The Judgement of Paris was burlesqued in the 1954 musical The Golden Apple. In it, the three goddesses have been reduced to three town biddies in smalltown Washington state. They ask Paris, a traveling salesman, to judge the cakes they have made for the church social. Each woman (the mayor's wife, the schoolmarm, and the matchmaker) makes appeals to Paris, who chooses the matchmaker. The matchmaker, in turn, sets him up with Helen, the town floozy, who runs off with him.

text: The Judgement of Paris is featured in the 2003 TV miniseries Helen of Troy. The event is brief, and only Hera and Aphrodite offer bribes. All three goddesses remain fully clothed. Aphrodite gives Paris a vision of Helen, while Helen has a reciprocal vision of Paris.

text: In the Hercules: The Legendary Journeys series, the contest is altered somewhat with Aphrodite and Athena entering but Artemis is the third goddess contestant instead of Hera (offering the one who chooses her the chance to be renowned as a great warrior). The Golden Apple appears as a gift from Aphrodite with the ability to make any mortal woman fall in love with the man holding it and to make a mortal man and woman soul mates if they simultaneously touch it. The other major differences beside the presence of Artemis and the role of the apple are the fact that it is Iolaus who is the judge and the goddesses appear in swimsuits and not nude.


document_title: Legal status of tattooing in the United States

question_text: whats the legal age to get a tattoo

question_tokens: whats the legal age to get a tattoo

text: In the United States, there is no federal law regulating the practice of tattooing. However, all 50 states and the District of Columbia have statutory laws requiring a person receiving a tattoo be 18 years or older. This is partially based on the legal principle that a minor cannot enter into a legal contract or otherwise render informed consent for a procedure. Most states permit a person under the age of 18 to receive a tattoo with permission of a parent or guardian, but some states outright prohibit tattooing under a certain age regardless of permission, with the exception of medical necessity (such as markings placed for radiation therapy).

text: In all jurisdictions, individual tattooists may also choose to place additional restrictions based on their own moral feelings, such as refusing any clients under a specific age even with parental consent despite it being legal, or limiting the type and/or location of where they are willing to tattoo (such as refusing any work around intimate parts of the body). They may additionally refuse to perform specific artwork, including if they merely find it inappropriate or offensive, or refuse to work on a client that they suspect may be intoxicated. Artists sometimes claim their personal business restrictions are a matter of law even when it is not true, so as to avoid arguments with clients.

text:
Legal Restrictions on Tattooing & Body Modification by State

State
Minimum Age (with parent/guardian consent)
Form of Parent/Guardian Consent
Notes & Exceptions
Intoxicated/Impaired Individuals
Area of Law/Type of Penalty
Licensing & Regulation
Relevant Statute(s) and Rules

Alabama
none specified[1]
informed written consent, signed in presence of the artist/service provider or their agent[1][2]
Ear piercing exempt from Alabama body art laws & rules.[2][3]
cannot be tattooed, branded, or pierced[1][2]
Violations of Alabama Tattoo & Body Piercing laws are a class c misdemeanor, punishable by a fine of up to $100 and/or up to 90 days imprisonment for each violation.[4]
Alabama's Department of Public Health licenses Tattoo, body piercing, & body art facilities, and sets standards for their operation.[5]
Individual tattoo artists, piercers, etc. require a permit.[2]

Ala. Code § 22-1-17A[3][6]
State Board of Health rules on Body Art Practices and Facilities.[2]

Alaska
18 (piercing excepted)[7]
parent/guardian must both give written consent and be present during the procedure[7]
Minors may be pierced with parental consent [7]
no restriction[8]

Alaska Stat. § 08.13.217[7]

Arizona
none specified[9]
parent/guardian must be physically present[9]
Minors can have their ears pierced with the written or verbal consent of a parent/guardian, can have procedures prescribed by a health care provider.[9]
no restriction[9]
Violations are a class 6 felony.[9]
There are no health regulations for tattoo shops in Arizona. [10]
Tattoos. Ariz. Rev. Stat. § 13-3721[9]

Arkansas
16[11]
parent/guardian must both give written consent and be physically present[12]
none specified[12]
cannot be tattooed, branded, or pierced.[12]

Ark. Stat. Ann. §§ 20-27-1501 et seq.[12]

California
18 (piercing excepted)[13][14]
parent/guardian must be present during procedure
Minors may have their ears pierced with parental consent.[15] They may be pierced elsewhere with parental consent, but not on their genitals or nipples. Permanent cosmetics are permitted on nipples, when done by a cosmetic technician and with parental consent.[14]
no restriction

Body Art. Cal. Health & Safety Code § 119300 to 119328[6][15]
Cal. Penal Code 653[13]

Colorado
18 Express written consent of parent or guardian[16]
parent/guardian must be present during procedure
Persons who are "noticeably impaired" cannot have body art procedures[16]

Body Artists. Colo. Rev. Stat. § 25-4-2101 to 2103[6]

Connecticut
none specified
permission of parent or guardian[17][18]
Minors may have their ears pierced without parental consent[17]
Tattooing may only be performed by physicians, or by registered nurses & technicians working under the supervision of a physician.[18]

no restrictions

Conn. Gen. Stat. §19a-92a,[6][18]
Conn. Gen. Stat. §19a-92g[6][17]

District of Columbia
18 (ear piercing excepted)[19]
written consent (for ear piercing)[19]
minors may have their ears pierced with written parental consent[19]
no restrictions[19]

Body Artists. DC Code § 47-2853.76d[6][19]

Delaware
18[20]
notarized written consent to the specific procedure[20]
none specified[20]
cannot be tattooed, branded, or body pierced[20]

Del. Code Ann. Title 11, Ch 5 §1114(a)[6][20]
Del. Code Ann. Title 16, Ch 2 §122(3)(w)[6]

Florida
16[21]
Must be accompanied by parent or guardian who can show proof of guardianship, both parent and minor must present photo ID, and a consent form must be notarized.[21]
for medical or dental purposes by a licensed physician or dentist[21]
no restriction

Fla. Stat. § 381.00787[6]
Fla. Stat. §381.0775 et seq.[6] Fla. Stat. §381.075[6]

Georgia
18 (body piercing excepted)[22]
For body piercing: prior written consent of parent/guardian[23]
Minors may have their ears pierced without parental consent[23]
Minors may be body pierced with written parental consent[23]
Physicians and Osteopaths or technicians working under their direct supervision can give minors tattoos or produce scars for "medical or cosmetic purposes."[22]
No one can be tattooed within an inch of their eye socket.[24]

no restrictions

Ga. Code § 31-40-1 to 31-40-10[6]
Ga. Code § 16-12-5[6]
Ga. Code § 16-5-71.1[6]

Hawaii
none specified[25]
written consent of parent/guardian[25]

Hawaii Rev. Stat. § 321-13[6]
Hawaii Rev. Stat. § 321-379[6]

Idaho
18[26]
Written informed consent of parent/guardian, executed in the presence of the person performing the procedure, or their agent/employee.[26]
Minors can have their ears pierced without parental consent.[6]
Piercing for medical procedures exempt.[6]

no restrictions

Idaho Code § 18-1523 (2004)[6]

Illinois
18 (body piercings excepted)[27]
Written consent of parent/guardian (for body piercings)[27]
Minors cannot be present in places where tattooing or body piercing is done except in the presence of a parent/guardian.[27]
Minors can have their ears pierced without parent/guardian consent.[27]

no restrictions

Ill. Stat. 720 §5/12-10.1[6]
Ill. Stat. 410 §54/1 t0 54/999[6]

Indiana
none specified[28]
Parent/guardian must both be present during the procedure and provide written permission.[28]
Minors may have their ears pierced without parental consent.[28]
no restrictions

Ind. Code Ann. §35-42-2-7[6][28]
Ind. Code Ann. §16-19-3-4.1[6][29]

Iowa
18[30]
n/a - minors cannot be tattooed[30]
Body piercing is not regulated by state law in Iowa, however county or city laws may regulate it.[31]
no restrictions

Iowa Code §135.37[6]
Iowa Code §135.37[6]

Kansas
16[32]
Parent/guardian must give written consent, written consent must be notarized, and the parent/guardian must be present during the procedure.[32]
Minors may have their ears pierced[33]
no restrictions

Kan. Stat. Ann. §65-1953[6]
Kan. Stat. Ann. §65-1940 to 65-1954[6]

Kentucky
16
Parent/guardian must give written, notarized consent.[34]
none (ear piercing also requires written, notarized consent).[35]

Ky. Rev. Stat. §211.760[6]
Ky. Rev. Stat. §194A.050; 211.760[6]

Louisiana
16
Parent or guardian must consent, and their presence during the procedure is required for tattoos, but not for body piercings.[36]

no restrictions

La. Rev. Stat. Ann. §14:93.2[6]
La. Rev. Stat. Ann. § 40:2831 et seq.[6]

Maine
18 (piercings excepted)[37]
For body piercings: prior legal consent of parent/guardian.[38]
Maine law does not require parent/guardian consent for ear piercing[39]
no restrictions

Me. Rev. Stat. Ann. Title 32 § 4201-4329[6]

Maryland
none specified[40]
written consent, which must be retained for 3 years.
Piercing of the ear lobe is exempt[41]
no restriction
Health Department Regulations
A license is not required, but any person performing tattooing or piercing must comply with all the relevant health code regulations[40]
COMAR 10.06.01.02 and 10.06.01.06

Massachusetts
18 (except body piercing other than genitalia)[42]
Minors cannot receive tattoo, branding, or scarification at all. For piercing of areas other than the genitalia, a parent may provide identification and sign the consent document.[42]
Physicians performing for treatment reasons and ear piercing are exempt from regulation.[42]
no restriction
County Health Department regulates body art, but all follow a model regulation set by the state.
Artists must have a permit, and establishments are subject to following specific health department regulations[42]
Model Regulations for Body Art Establishments[42]

Michigan
none specified[43]
Written, informed consent of parent/guardian. Must be executed (signed) in the presences of the person performing the procedure, or their employee.[43]

cannot be tattooed, branded, or body pierced.[43]

Mich. Comp. Laws § 333.13101 to 333.13112[44]

Minnesota
18 (piercings excepted)[45]
For piercings: presence of parent/guardian and a consent form are both required.[45]
Minors cannot be tattooed. They can be body pierced, but not in the nipples or genitals. Branding, scarification, suspension, subdermal implantation, microdermal, and tongue bifurcation are also prohibited for minors.[45]
cannot have any body art procedures.[45]

Minnesota Statutes 146B.07[45]

Mississippi
18
n/a - minors cannot be tattooed
piercing also prohibited except for the outer perimeter or lobe of the ear.
no restriction

Miss.Code Ann. §73-61

Missouri
none specified[46]
For both piercings and tattoos, parent/guardian must sign written consent in the presence of the person performing the procedure, or their employee.[46]

cannot be tattooed, branded or body pierced.[46]
violations are a misdemeanor, punishable with a fine of up to $500 (more for repeat offenses)[46]
The state director of the division of professional registration licenses all body artists, and sets rules & regulations for the operation of body art establishments.[47]
Mo. Rev. Stat. §324.520[46]

Montana
none specified[48]
Parent or guardian must give "explicit, in-person" consent.[48] Montana administrative rules also require that the parent/guardian be present throughout the procedure.[49]

cannot be tattooed or body pierced.[49]
A person who tattoos or body pierces a minor without parent/guardian consent is guilty of Unlawful transactions with children, punishable by a fine of up to $500 or six months in county jail, or both.[48]
Other violations of Montana body art laws are a misdemeanor, with punishments ranging from a fine of $50–100 for a first offense to $300 and/or 90 days in county jail for third and subsequent offense.[50]

Montana's Department of Health and Safety licenses and regulates body art establishments.[51] Local health boards may establish their own licensing and regulatory schemes in lieu of the state department's.[52]
Mont. Code Ann. §45-5-623[48]
Mont. Code Ann. §50-48-101 to 110[53]
Mont. Code Ann. §50-48-201 to 209[54]

Nebraska
none specified[55]
written consent, must be present during procedure
Piercing does not include the external parts of the ear[56]
No restrictions

Nebraska Revised Statute 38-1008, 38-1009, 38-1010, 38-1011, 38-1060, 38-10,165

Nevada
n/a[6]
n/a[6]
Nevada state law does not regulate tattoos, piercings, or other body art. Regional health districts may regulate the practice. The southern Nevada Health District, for example, does not allow minors below the age of 14 to be tattooed, and requires a parent or guardian to provide written consent and be present during the procedure for 14- to 18-year-olds. The southern Nevada district also bans tattoos on those who are under the influence of drugs or alcohol.[57]
n/a[6]

n/a[6]

New Hampshire
18 (piercings excepted)[58]
For piercings: parent/guardian must both sign written consent and be present during the procedure.
Minors cannot be tattooed or branded. They may be pierced with parent/guardian consent.[58] Minors may have their ears pierced without parent/guardian consent.[59]
no restrictions

N.H. Rev. Stat. Ann. § 314[6]

New Jersey
none specified[60]
written permission of parent/guardian is required for tattooing and body piercing.[60]
Parent/guardian must be present and sign written consent for ear piercings as well as for body piercing. Minors cannot have genital piercings even with parent/guardian consent.[61]
no restrictions
no restrictions
no restrictions
N.J. Stat. Ann. §2C:40-21
N.J.A.C. 8:27-1 et seq.
N.J. Stat. Ann. §26-1A-7[6]

New Mexico
none specified[62]
Written consent and presence during the procedure.
Medical procedures by physicians and ear piercing are exempt[63]
no restrictions
Administrative Regulations set by the Board of Barbers and Cosmetologists
All body artists are required to be licensed through the state, and are subject to regulations from the Board
Body Art Safe Practices Act. N.M. Stat. Ann. § 61-17B et seq.,[63] N.M. Administrative Code 16.36 et seq.[62]

New York
18 (piercings excepted) [64]
Minors cannot be tattooed with parent/guardian consent. For piercings: parent/guardian must give written consent, signed in presence of the body artist or body art establishment owner.[65]
Written parental consent is not required for ear piercings.[66]
no restrictions

New York Public Health Law, Article 4-A[6][65]
N.Y. Public Health Law §460-466[6]
N.Y. Penal Law § 260.21[6]

North Carolina
18 (piercings excepted)[67]
Minors cannot be tattooed, even with parent/guardian consent. "Prior consent" of parent/guardian is required for body piercings.[67]
Minors may have their ears pierced without parental consent.[67]
no restrictions

N.C. Gen. Stat. § 130A-283[68]
N.C. Gen. Stat. § 14-400[69]

North Dakota
none specified[70]
Parent/guardian must be present during the procedure and give written consent.[70]

cannot get tattoos or other body art[71]

N.D. Code §23-01-35[72]
N.D. Code §12.1-31-13[6][70]

Ohio
none specified[73]
Parent/guardian must both sign a consent form and "appear in person at the business at the time the procedure is performed."[73]
none - parent/guardian consent and presence is also required for ear piercings.[73]
no restrictions

Ohio Rev. Code Ann. §3730.01 to 3730.99[6][73]

Oklahoma
18 (piercings excepted)[74]
Minors cannot be tattooed, even with parent/guardian consent. For piercings: parent/guardian must both give written consent and be present during the procedure.[74]
Ear piercing is not governed/restricted by Oklahoma law.[74]
Scleral tattooing is illegal.[74]

cannot be tattooed.[74]

Okla. Stat. Title 21 §842.1, 842.2, 842.3[6]

Oregon
18 (piercings excepted)[75]
For piercings: parent/guardian must give written consent and present proof of identity.[76][77]
Minors can only be tattooed with the authorization of a physician.[75]
Scarification and dermal implants are prohibited[78]
Persons with sunburns or skin diseases or disorders cannot be tattooed or pierced.[75][77]
Minors cannot be pierced on the genitals or nipples, even with parent/guardian consent.[76]
Piercing on testes, deep shaft (corpus cavernosa), uvula, eyelids and sub-clavicle are all prohibited.[77]

cannot be tattooed or pierced.[75][77]
Violations of Oregon body art laws are a misdemeanor.[79]
Violations of Health Licensing Office rules are fined (various amounts).[80]

Both body artists and body art establishments are licensed by the Oregon Health Licensing Office.[81] With the assistance of a Board of Body Art practitioners, the Health Licensing Office also sets detailed rules and regulations for body art.[82]
Or. Rev. Stat. § 690.350 et seq
Or. Rev. Stat. § 690.401 to 410
Or. Rev. Stat. § 679.500[6]
Health Licensing Office Rules, especially Divisions 900, 905, 915 & 920[82]

Pennsylvania
none specified[83]
parent/guardian must both give consent and be present during the procedure.[83]

no restrictions

Pa. Cons. Stat. Title 18 § 6311[6][83]

Rhode Island
18 (piercings excepted)[84][85]
Minors cannot be tattooed.[84] For piercings: parent/guardian must both give consent and be present for the procedure.[85]

no restrictions
Tattooing a minor is a criminal offense (misdemeanor), maximum fine $300[84]
Tattooing and body art are regulated by the department of health, artists must be registered.[85]
RI Gen L § 23-1-39[85]
RI Gen L § 11-9-15[84]

South Carolina
18 (piercings excepted)[86][87]
Minors cannot be tattooed.[86] For piercings: parent/guardian must either give written, notarized consent or be present during the procedure.[87]
Head, face, and neck tattoos are illegal.[86]
cannot be tattooed or body pierced[86][88]
Under the Health Code, persons violating restrictions on tattooing and body piercing are guilty of a misdemeanor. Upon conviction, they may be fined up to $2500 or imprisoned for a year, or both.[86][87]
Tattoo and body piercing facilities are regulated by the Department of Health and Environmental Control. Tattoo facilities are licensed, body piercing facilities require a permit, and artists must be registered[89][90]
S.C. Code § 44-32-10 to 44-32-120[88]
S.C. Code § 44-34-10 to 44-34-110[91]

South Dakota
none specified[92]
Parent/guardian must sign a consent form.[92]

cannot be tattooed or pierced[93][94]
Tattooing a minor is a class 2 misdemeanor.[95]
Tattooing and Body Piercing are governed by Department of Health rules.[96] Municipalities may set stricter regulations, and have the authority to license body artists.[95]
S.D. Codified Laws Ann. §26-10-19[92]
S.D. Laws § 9-34-17[95]

Tennessee
18 (piercings excepted)[97][98]
For tattoos that cover an existing tattoo (see Notes & Exceptions): Parent/Guardian must be present during the procedure.[97]
For piercings: Parent/Guardian must give written consent, be present during the procedure.[98]

Minors over the age of sixteen may be tattooed to cover up an existing tattoo, with parent/guardian consent.[97]

Minors who lie about their age to be tattooed are guilty of a "delinquent act," are required to pay a fine of $50–$250 and serve at least 20 hours of community service.[97]
Tattooing a minor is a class a misdemeanor,[97] breach of body piercing law is a class b misdemeanor.[99]

Tattoo artists and body piercers are licensed by the state department of health, tattoo shops require a certificate from the local health department.[100][101]
Tenn. Code §§ 62-38-201-310[102]

Texas
18 (piercings excepted)[103][104]
For body piercings and for covering existing tattoos (see Notes & Exceptions): Parent/guardian must be present during procedure, sign an affidavit[103][104]
Ear piercing is exempt from body piercing statutes[105]
Minors may, with parent/guardian consent, be tattooed to cover up an existing tattoo that has offensive, gang-related, or drug-related content, or "other words, symbols, or markings that the person's parent or guardian considers would be in the best interest of the person to cover"[103]
Tongue splitting prohibited.[106]

Cannot be tattooed or pierced.[103][107]
Misrepresenting one's age to get a tattoo, or to get a piercing without parental consent, is a class B misdemeanor[103][104]
Violations of Texas tattooing & body piercing statute are a Class A misdemeanor, with each day of violation counting as a separate offense.[108]
Health Commissioner can impose a fine of up to $5000 on artists & shops for each violation[109]

Tattoo artists and body piercers must be registered with the Texas Department of Health[110] Tattoo and body piercing shops must be licensed[111]
Texas Health and Safety Code Ann. §146[112]

Utah
none specified[113]
Parent/guardian must be present during the procedure, give written permission, and provide proof of identity.[113]
Parental consent not required by law for ear piercing[113]

Tattooing or body piercing a minor is a class b misdemeanor, shops can be fined up to $1000 for each violation.[113]

Utah Code Ann. §76-10-2201[6]

Vermont
none specified[114]

Tattooists and body piercers must be registered.[114]
Vt. Stat. Ann. Title 26 §4101 to 4109[6][115]

Virginia
none specified[116]
Parent/Guardian must be present during the procedure.[116]
Virginia law does not limit minors' ability to have their ears pierced.[116]

Tattooing or body piercing a minor is a class 1 misdemeanor[116]
Tattoo artists and body piercers, as well as the operators of tattoo and body piercing establishments, are licensed by the state.[117][118]
Civic/local governments are empowered to regulate tattoo and body piercing establishments.[119]

Va. Code §54.1-700 et seq.
Va. Code §15.2-912
Va. Code § 18.2-371.3.[6]

Washington
18 (piercings excepted)[120]

cannot have tattoos, body piercings, or other body art.[121]

Wash. Code §26.28.085[120]
Wash. Code § 18.300[122]
Wash. Code § 246-145-001 to 060[123]
Wash. Code §70.54[124]

West Virginia
none specified[125]
parent/guardian must give written consent[125]

All persons receiving a tattoo must attest they are not under the influence of drugs or alcohol.[125]

Tattoo shop owners and body piercing studios must register with local board of health, and must be registered as a business with the state[126][127][128]
W. Va. Code §16-37
W. Va. Code §16-38[129]

Wisconsin
18[130]
n/a (tattooing not permitted under 18)
Physicians in the course of professional practice are exempt
no restriction
Tattooing a minor or even offering to do so is subject to a fine of up to $200
Artists must be satisfy training requirements and obtain a license from the health department. Establishments are subject to inspection and licensing[131]
Wisconsin Statutes & Annotations 948.70 and 252.235

Wyoming
none specified[132]
Verbal consent, presence during procedure.[132]
Procedures performed under the supervision of a licensed physician, and piercing of the ear, do not count as body art for this law.
no restriction[132]
Misdemeanor criminal offense, punishable by fine and prison time[132]

Wyoming Statute §14-3-107[132]

tag: table


document_title: Glimpses of World History

question_text: who is the author of glimpses of world history

text: Glimpses of World History

text:
Glimpses of World History

Author
Jawaharlal Nehru

Genre
History

Publisher
Penguin Books

Pages
1192

ISBN
978-0-19-562360-4

OCLC
21227307

text: Glimpses of World History, a book published by Jawaharlal Nehru in 1934, is a panoramic sweep of the history of humankind. It is a collection of 196 letters on world history written from various prisons in British India between 1930–1933. The letters were written to his young daughter Indira, and were meant to introduce her to world history.[1]

text: The letters start off with one he sends to his daughter on her birthday. He says he is sad about not being able to send her any "material" gift from prison, so he would try to give her something he can "afford", a series of letters from his heart.

text: Written from prison, where he had no recourse to reference books or a library but his personal notes, Glimpses of World History contains the history of humankind from 6000 BC to the time of writing of the book. It covers the rise and fall of great empires and civilizations from Greece and Rome to China and West Asia; great figures such as Ashoka and Genghis Khan, Mohandas K. Gandhi and Vladimir Lenin; wars and revolutions, democracies and dictatorships.

text: He wrote about many cultures throughout the globe in detail because, as he himself said, he didn't like the way history was taught in schools where it was confined to the history of a single country and that too narrow, and he wanted his daughter Indira to know why people did what they did. It was possible only through knowing the history of the whole world.

text: The letters are written in informal language, with contemporary and personal events also mentioned. They reflect the world view of Nehru, and his grasp of history. It could be considered as one of the first attempts at historiography from a non-Eurocentric angle - a statement that is itself subject to the charge of Eurocentrism, given the long history of historical writing outside of Europe, for instance in China (from The Classic of History, c. 550 BC) or the Islamic world (from Muhammad ibn Jarir al-Tabari in the 9th century AD to Biruni and Ibn Khaldun).

text: Nehru stated in his preface that The Outline of History by H. G. Wells was a major influence on the work.[2] The New York Times described it as: "... one of the most remarkable books ever written.... Nehru makes even H.G. Wells seem singularly insular..... One is awed by the breadth of Nehru's culture."[3]

text: In particular, his chapter on Genghis Khan and the Mongol invasion runs counter to dominant European views of the time. Prefacing his introduction to the Mongol empire, which was larger than the British empire and lasted as long, he said: "It would be foolish not to recognize the greatness of Europe. But it would be equally foolish to forget the greatness of Asia."

text: And he goes on to state: "Genghis is, without doubt, the greatest military genius and leader in history.... Alexander and Caesar seem petty before him." According to Jack Weatherford,[4] this was possibly the first re-evaluation of the Mongol empire since the 18th century.

text: Nehru's interpretation of the Sepoy Mutiny—sparked by the order for the Sepoys to bite off the paper cartridges for their rifles which were greased with animal fat, namely beef and pork—is that "the Revolt of 1857-58 was the last flicker of feudal India."[5]

text: Sources[edit]

text: Nehru, Jawaharlal. Glimpses of World History. Penguin Books India. ISBN 0-670-05818-1