To isolate pure silicon, chemists react quartz sand with magnesium. Silicon is also smelted at high temperatures and even “grown.” The Czochralski method uses pressure, temperature and silicon compounds to produce crystals of a pure substance.
Life
Silicon compounds are actively used in everyday life, human households, and in industry. Quartz sand is used in the production of glass and cement. The silicate industry is named after silicon, whose middle name is silicium. Silicates are used in agriculture to fertilize the soil. Silicate glue is also produced based on silicon compounds.Radioelectronics
Silicon has unique radioelectronic properties. Pure silicon is a semiconductor. This means that it can conduct current under certain conditions when the conduction band is small. If the conduction region is large, semiconductor silicon turns into insulating silicon.The semiconducting properties of the non-metal silicon led to the creation of the transistor. A transistor is a device that allows you to control voltage and current. Unlike linear conductors, silicon transistors have three main elements - a collector, which “collects” the current, a base and an emitter, which amplifies the current. The appearance of the transistor caused the “electronic boom” and led to the creation of the first computers and household appliances.
Computers
The successes of silicon in electronics have not gone unnoticed in computer technology. At first, they wanted to make processors from “expensive” typical semiconductors, for example. However, its high price did not allow the production of germanium circuit boards to be put into production. Then the brave souls from IBM decided to take a risk and try silicon as a material for the “heart” of a computer system. The results were not long in coming.Silicon boards turned out to be quite cheap, which was especially important at the very beginning of the computer industry, when there were many defects and few potential buyers.
Today, silicon chips dominate the computer industry. They have learned to grow pure silicon crystals for processors and controllers in factory conditions; the material is easy to use. And most importantly, silicon allowed the number of elements on a processor to double every two years (Moore's Law). Thus, there are more and more transistors and other logic elements on the same size silicon circuit. Silicon has made it possible to make information technology as efficient as possible.
After oxygen silicon is the most abundant element in the earth's crust. It has 2 stable isotopes: 28 Si, 29 Si, 30 Si. Silicon does not occur in free form in nature.
The most common: silicic acid salts and silicon oxide (silica, sand, quartz). They are part of mineral salts, mica, talc, asbestos.
Allotropy of silicon.
U silicon There are 2 allotropic modifications:
Crystalline (light gray crystals. The structure is similar to the diamond crystal lattice, where the silicon atom is covalently bonded to 4 identical atoms, and itself is in sp3 - hybridization);
Amorphous (brown powder, more active form than crystalline).
Properties of silicon.
At temperature, silicon reacts with oxygen in the air:
Si + O 2 = SiO 2 .
If there is not enough oxygen (lack of oxygen), then the following reaction may occur:
2 Si + O 2 = 2 SiO,
Where SiO- monoxide, which can also be formed during the reaction:
Si + SiO 2 = 2 SiO.
Under normal conditions silicon may react with F 2 , when heated - with Cl 2 . If you increase the temperature further, then Si will be able to interact with N And S:
4Si + S 8 = 4SiS 2 ;
Si + 2F 2 = SiF 4.
Silicon is capable of reacting with carbon, giving carborundum:
Si + C = SiC.
Silicon is soluble in a mixture of concentrated nitric and hydrofluoric acids:
3Si + 4HNO 3 + 12HF = 3SiF 4 + 4NO + 8H 2 O.
Silicon dissolves in aqueous solutions of alkalis:
Si + 2NaOH + H 2 O = Na 2 SiO 3 + H 2.
When heated with oxides, silicon disproportionates:
2 MgO + 3 Si = Mg 2 Si + 2 SiO.
When interacting with metals, silicon acts as an oxidizing agent:
2 Mg + Si = Mg 2 Si.
Application of silicon.
Silicon is most widely used in the production of alloys for imparting strength to aluminum, copper and magnesium and for the production of ferrosilicides, which are important in the production of steels and semiconductor technology. Silicon crystals are used in solar cells and semiconductor devices - transistors and diodes.
Silicon also serves as a raw material for the production of organosilicon compounds, or siloxanes, obtained in the form of oils, lubricants, plastics and synthetic rubbers. Inorganic silicon compounds are used in ceramic and glass technology, as an insulating material and piezocrystals.
Silicon(lat. silicium), si, chemical element of group IV of the periodic system of Mendeleev; atomic number 14, atomic mass 28.086. In nature, the element is represented by three stable isotopes: 28 si (92.27%), 29 si (4.68%) and 30 si (3.05%).
Historical reference . K compounds, widespread on earth, have been known to man since the Stone Age. The use of stone tools for labor and hunting continued for several millennia. The use of K compounds associated with their processing - production glass - began around 3000 BC. e. (in Ancient Egypt). The earliest known compound of K. is dioxide sio 2 (silica). In the 18th century silica was considered a simple body and referred to as “earths” (as reflected in its name). The complexity of the composition of silica was established by I. Ya. Berzelius. For the first time, in 1825, he obtained elemental calcium from silicon fluoride sif 4, reducing the latter with potassium metal. The new element was given the name “silicon” (from the Latin silex - flint). The Russian name was introduced by G.I. Hess in 1834.
Prevalence in nature . In terms of prevalence in the earth's crust, oxygen is the second element (after oxygen), its average content in the lithosphere is 29.5% (by mass). In the earth's crust, carbon plays the same primary role as carbon in the animal and plant world. For the geochemistry of oxygen, its extremely strong connection with oxygen is important. About 12% of the lithosphere is silica sio 2 in mineral form quartz and its varieties. 75% of the lithosphere consists of various silicates And aluminosilicates(feldspars, micas, amphiboles, etc.). The total number of minerals containing silica exceeds 400 .
During magmatic processes, weak differentiation of calcium occurs: it accumulates both in granitoids (32.3%) and in ultrabasic rocks (19%). At high temperatures and high pressure, the solubility of sio 2 increases. Its migration with water vapor is also possible, therefore pegmatites of hydrothermal veins are characterized by significant concentrations of quartz, which is often associated with ore elements (gold-quartz, quartz-cassiterite, etc. veins).
Physical and chemical properties. Carbon forms dark gray crystals with a metallic luster, having a face-centered cubic diamond-type lattice with a period a = 5.431 a, and a density of 2.33 g/cm 3 . At very high pressures, a new (apparently hexagonal) modification with a density of 2.55 g/cm 3 was obtained. K. melts at 1417°C, boils at 2600°C. Specific heat capacity (at 20-100°C) 800 J/ (kg? K), or 0.191 cal/ (g? deg); thermal conductivity even for the purest samples is not constant and is in the range (25°C) 84-126 W/ (m? K), or 0.20-0.30 cal/ (cm? sec? deg). Temperature coefficient of linear expansion 2.33? 10 -6 K -1 ; below 120k it becomes negative. K. is transparent to long-wave infrared rays; refractive index (for l =6 µm) 3.42; dielectric constant 11.7. K. is diamagnetic, atomic magnetic susceptibility is -0.13? 10 -6. K. hardness according to Mohs 7.0, according to Brinell 2.4 Gn/m2 (240 kgf/mm2), elastic modulus 109 Gn/m2 (10890 kgf/mm2), compressibility coefficient 0.325? 10 -6 cm 2 /kg. K. brittle material; noticeable plastic deformation begins at temperatures above 800°C.
K. is a semiconductor that is finding increasing use. The electrical properties of copper are very dependent on impurities. The intrinsic specific volumetric electrical resistivity of a cell at room temperature is taken to be 2.3? 10 3 ohm? m(2,3 ? 10 5 ohm? cm) .
Semiconductor circuit with conductivity R-type (additives B, al, in or ga) and n-type (additives P, bi, as or sb) has significantly lower resistance. The band gap according to electrical measurements is 1.21 ev at 0 TO and decreases to 1.119 ev at 300 TO.
In accordance with the position of the ring in the periodic table of Mendeleev, the 14 electrons of the ring atom are distributed over three shells: in the first (from the nucleus) 2 electrons, in the second 8, in the third (valence) 4; electron shell configuration 1s 2 2s 2 2p 6 3s 2 3p 2. Successive ionization potentials ( ev): 8.149; 16.34; 33.46 and 45.13. Atomic radius 1.33 a, covalent radius 1.17 a, ionic radii si 4+ 0.39 a, si 4- 1.98 a.
In carbon compounds (similar to carbon) 4-valentene. However, unlike carbon, silica, along with a coordination number of 4, exhibits a coordination number of 6, which is explained by the large volume of its atom (an example of such compounds are silicofluorides containing the 2- group).
The chemical bond of a carbon atom with other atoms is usually carried out due to hybrid sp 3 orbitals, but it is also possible to involve two of its five (vacant) 3 d- orbitals, especially when K. is six-coordinate. Having a low electronegativity value of 1.8 (versus 2.5 for carbon; 3.0 for nitrogen, etc.), carbon is electropositive in compounds with nonmetals, and these compounds are polar in nature. High binding energy with oxygen si-o, equal to 464 kJ/mol(111 kcal/mol) , determines the stability of its oxygen compounds (sio 2 and silicates). Si-si binding energy is low, 176 kJ/mol (42 kcal/mol) ; Unlike carbon, carbon is not characterized by the formation of long chains and double bonds between Si atoms. In air, due to the formation of a protective oxide film, carbon is stable even at elevated temperatures. In oxygen it oxidizes starting at 400°C, forming silicon dioxide sio 2. Sio monoxide is also known, stable at high temperatures in the form of a gas; as a result of sudden cooling, a solid product can be obtained that easily decomposes into a thin mixture of si and sio 2. K. is resistant to acids and dissolves only in a mixture of nitric and hydrofluoric acids; easily dissolves in hot alkali solutions with the release of hydrogen. K. reacts with fluorine at room temperature and with other halogens when heated to form compounds of the general formula six 4 . Hydrogen does not react directly with carbon, and silicic acids(silanes) are obtained by decomposition of silicides (see below). Hydrogen silicones are known from sih 4 to si 8 h 18 (the composition is similar to saturated hydrocarbons). K. forms 2 groups of oxygen-containing silanes - siloxanes and siloxenes. K reacts with nitrogen at temperatures above 1000°C. Of great practical importance is si 3 n 4 nitride, which does not oxidize in air even at 1200°C, is resistant to acids (except nitric) and alkalis, as well as molten metals and slags, which makes it a valuable material for the chemical industry, for production of refractories, etc. Compounds of carbon with carbon are distinguished by their high hardness, as well as thermal and chemical resistance ( silicon carbide sic) and with boron (sib 3, sib 6, sib 12). When heated, chlorine reacts (in the presence of metal catalysts, such as copper) with organochlorine compounds (for example, ch 3 cl) to form organohalosilanes [for example, si (ch 3) 3 ci], which are used for the synthesis of numerous organosilicon compounds.
K. forms compounds with almost all metals - silicides(connections only with bi, tl, pb, hg were not detected). More than 250 silicides have been obtained, the composition of which (mesi, mesi 2, me 5 si 3, me 3 si, me 2 si, etc.) usually does not correspond to classical valencies. Silicides are refractory and hard; Ferrosilicon and molybdenum silicide mosi 2 are of greatest practical importance (electric furnace heaters, gas turbine blades, etc.).
Receipt and application. K. technical purity (95-98%) is obtained in an electric arc by the reduction of silica sio 2 between graphite electrodes. In connection with the development of semiconductor technology, methods have been developed for obtaining pure and especially pure copper. This requires the preliminary synthesis of the purest starting compounds of copper, from which copper is extracted by reduction or thermal decomposition.
Pure semiconductor copper is obtained in two forms: polycrystalline (by reduction of sici 4 or sihcl 3 with zinc or hydrogen, thermal decomposition of sil 4 and sih 4) and single-crystalline (crucible-free zone melting and “pulling” a single crystal from molten copper - the Czochralski method).
Specially doped copper is widely used as a material for the manufacture of semiconductor devices (transistors, thermistors, power rectifiers, controlled diodes - thyristors; solar photocells used in spacecraft, etc.). Since K. is transparent to rays with wavelengths from 1 to 9 µm, it is used in infrared optics .
K. has diverse and ever-expanding areas of application. In metallurgy, oxygen is used to remove oxygen dissolved in molten metals (deoxidation). K. is a component of a large number of alloys of iron and non-ferrous metals. Usually, carbon gives alloys increased resistance to corrosion, improves their casting properties, and increases mechanical strength; however, with a higher content of K. it can cause fragility. The most important are iron, copper, and aluminum alloys containing calcium. An increasing amount of carbon is used for the synthesis of organosilicon compounds and silicides. Silica and many silicates (clays, feldspars, mica, talc, etc.) are processed by the glass, cement, ceramic, electrical, and other industries.
V. P. Barzakovsky.
Silicon is found in the body in the form of various compounds, mainly involved in the formation of hard skeletal parts and tissues. Some marine plants (for example, diatoms) and animals (for example, siliceous sponges, radiolarians) can accumulate especially large amounts of silicon, forming thick deposits of silicon dioxide on the ocean floor when they die. In cold seas and lakes, biogenic silts enriched in potassium predominate; in tropical seas, calcareous silts with a low content of potassium predominate. Among land plants, cereals, sedges, palms, and horsetails accumulate a lot of potassium. In vertebrates, the content of silicon dioxide in ash substances is 0.1-0.5%. In the largest quantities, K. is found in dense connective tissue, kidneys, and pancreas. The daily human diet contains up to 1 G K. When there is a high content of silicon dioxide dust in the air, it enters the human lungs and causes disease - silicosis.
V. V. Kovalsky.
Lit.: Berezhnoy A.S., Silicon and its binary systems. K., 1958; Krasyuk B. A., Gribov A. I., Semiconductors - germanium and silicon, M., 1961; Renyan V.R., Technology of semiconductor silicon, trans. from English, M., 1969; Sally I.V., Falkevich E.S., Production of semiconductor silicon, M., 1970; Silicon and germanium. Sat. Art., ed. E. S. Falkevich, D. I. Levinzon, V. 1-2, M., 1969-70; Gladyshevsky E.I., Crystal chemistry of silicides and germanides, M., 1971; wolf N. f., silicon semiconductor data, oxf. - n. y., 1965.
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Silicon
SILICON-I; m.[from Greek krēmnos - cliff, rock] Chemical element (Si), dark gray crystals with a metallic sheen are found in most rocks.
◁ Silicon, oh, oh. K salts. Siliceous (see 2.K.; 1 mark).
silicon(lat. Silicium), chemical element of group IV of the periodic table. Dark gray crystals with a metallic luster; density 2.33 g/cm 3, t pl 1415ºC. Resistant to chemical influences. It makes up 27.6% of the mass of the earth's crust (2nd place among elements), the main minerals are silica and silicates. One of the most important semiconductor materials (transistors, thermistors, photocells). An integral part of many steels and other alloys (increases mechanical strength and corrosion resistance, improves casting properties).
SILICONSILICON (lat. Silicium from silex - flint), Si (read “silicium”, but nowadays quite often as “si”), a chemical element with atomic number 14, atomic mass 28.0855. The Russian name comes from the Greek kremnos - cliff, mountain.
Natural silicon consists of a mixture of three stable nuclides (cm. NUCLIDE) with mass numbers 28 (prevails in the mixture, it contains 92.27% by mass), 29 (4.68%) and 30 (3.05%). Configuration of the outer electronic layer of a neutral unexcited silicon atom 3 s 2
R 2
. In compounds it usually exhibits an oxidation state of +4 (valence IV) and very rarely +3, +2 and +1 (valency III, II and I, respectively). In the periodic table of Mendeleev, silicon is located in group IVA (in the carbon group), in the third period.
The radius of a neutral silicon atom is 0.133 nm. The sequential ionization energies of the silicon atom are 8.1517, 16.342, 33.46 and 45.13 eV, and the electron affinity is 1.22 eV. The radius of the Si 4+ ion with a coordination number of 4 (the most common in the case of silicon) is 0.040 nm, with a coordination number of 6 - 0.054 nm. According to the Pauling scale, the electronegativity of silicon is 1.9. Although silicon is usually classified as a non-metal, in a number of properties it occupies an intermediate position between metals and non-metals.
In free form - brown powder or light gray compact material with a metallic sheen.
History of discovery
Silicon compounds have been known to man since time immemorial. But man became acquainted with the simple substance silicon only about 200 years ago. In fact, the first researchers to obtain silicon were the French J. L. Gay-Lussac (cm. GAY LUSSAC Joseph Louis) and L. J. Tenard (cm. TENAR Louis Jacques). They discovered in 1811 that heating silicon fluoride with potassium metal leads to the formation of a brown-brown substance:
SiF 4 + 4K = Si + 4KF, however, the researchers themselves did not draw the correct conclusion about obtaining a new simple substance. The honor of discovering a new element belongs to the Swedish chemist J. Berzelius (cm. BERZELIUS Jens Jacob), who also heated a compound of composition K 2 SiF 6 with potassium metal to produce silicon. He obtained the same amorphous powder as the French chemists, and in 1824 announced a new elemental substance, which he called “silicon.” Crystalline silicon was obtained only in 1854 by the French chemist A. E. Sainte-Clair Deville (cm. SAINT-CLAIR DEVILLE Henri Etienne) .
Being in nature
In terms of abundance in the earth's crust, silicon ranks second among all elements (after oxygen). Silicon accounts for 27.7% of the mass of the earth's crust. Silicon is a component of several hundred different natural silicates (cm. SILICATES) and aluminosilicates (cm. ALUMINUM SILICATES). Silica, or silicon dioxide, is also widespread (cm. SILICON DIOXIDE) SiO 2 (river sand (cm. SAND), quartz (cm. QUARTZ), flint (cm. FLINT) etc.), constituting about 12% of the earth's crust (by mass). Silicon does not occur in free form in nature.
Receipt
In industry, silicon is produced by reducing the SiO 2 melt with coke at a temperature of about 1800°C in arc furnaces. The purity of the silicon obtained in this way is about 99.9%. Since silicon of higher purity is needed for practical use, the resulting silicon is chlorinated. Compounds of the composition SiCl 4 and SiCl 3 H are formed. These chlorides are further purified in various ways from impurities and at the final stage they are reduced with pure hydrogen. It is also possible to purify silicon by first obtaining magnesium silicide Mg 2 Si. Next, volatile monosilane SiH 4 is obtained from magnesium silicide using hydrochloric or acetic acids. Monosilane is further purified by rectification, sorption and other methods, and then decomposed into silicon and hydrogen at a temperature of about 1000°C. The impurity content in silicon obtained by these methods is reduced to 10 -8 -10 -6% by weight.
Physical and chemical properties
Crystal lattice of silicon face-centered cubic diamond type, parameter a = 0.54307 nm (other polymorphic modifications of silicon have been obtained at high pressures), but due to the longer bond length between Si-Si atoms compared to the length of the C-C bond, the hardness of silicon is significantly less than that of diamond.
Silicon density is 2.33 kg/dm3. Melting point 1410°C, boiling point 2355°C. Silicon is fragile, only when heated above 800°C does it become a plastic substance. Interestingly, silicon is transparent to infrared (IR) radiation.
Elemental silicon is a typical semiconductor (cm. SEMICONDUCTORS). The band gap at room temperature is 1.09 eV. The concentration of current carriers in silicon with intrinsic conductivity at room temperature is 1.5·10 16 m -3. The electrical properties of crystalline silicon are greatly influenced by the microimpurities it contains. To obtain silicon single crystals with hole conductivity, additives of group III elements - boron - are introduced into silicon. (cm. BOR (chemical element)), aluminum (cm. ALUMINUM), gallium (cm. GALLIUM) and India (cm. INDIUM), with electronic conductivity - additions of elements of group V - phosphorus (cm. PHOSPHORUS), arsenic (cm. ARSENIC) or antimony (cm. ANTIMONY). The electrical properties of silicon can be varied by changing the processing conditions of single crystals, in particular, by treating the silicon surface with various chemical agents.
Chemically, silicon is inactive. At room temperature it reacts only with fluorine gas, resulting in the formation of volatile silicon tetrafluoride SiF 4 . When heated to a temperature of 400-500°C, silicon reacts with oxygen to form dioxide SiO 2, with chlorine, bromine and iodine to form the corresponding highly volatile tetrahalides SiHal 4.
Silicon does not react directly with hydrogen; silicon compounds with hydrogen are silanes (cm. SILANS) with the general formula Si n H 2n+2 - obtained indirectly. Monosilane SiH 4 (often called simply silane) is released when metal silicides react with acid solutions, for example:
Ca 2 Si + 4HCl = 2CaCl 2 + SiH 4
The silane SiH 4 formed in this reaction contains an admixture of other silanes, in particular, disilane Si 2 H 6 and trisilane Si 3 H 8, in which there is a chain of silicon atoms interconnected by single bonds (-Si-Si-Si-) .
With nitrogen, silicon at a temperature of about 1000°C forms the nitride Si 3 N 4, with boron - the thermally and chemically stable borides SiB 3, SiB 6 and SiB 12. A compound of silicon and its closest analogue according to the periodic table - carbon - silicon carbide SiC (carborundum (cm. CARBORUNDUM)) is characterized by high hardness and low chemical reactivity. Carborundum is widely used as an abrasive material.
When silicon is heated with metals, silicides form (cm. SILICIDES). Silicides can be divided into two groups: ionic-covalent (silicides of alkali, alkaline earth metals and magnesium such as Ca 2 Si, Mg 2 Si, etc.) and metal-like (silicides of transition metals). Silicides of active metals decompose under the influence of acids; silicides of transition metals are chemically stable and do not decompose under the influence of acids. Metal-like silicides have high melting points (up to 2000°C). Metal-like silicides of the compositions MSi, M 3 Si 2, M 2 Si 3, M 5 Si 3 and MSi 2 are most often formed. Metal-like silicides are chemically inert and resistant to oxygen even at high temperatures.
Silicon dioxide SiO 2 is an acidic oxide that does not react with water. Exists in the form of several polymorphs (quartz (cm. QUARTZ), tridymite, cristobalite, glassy SiO 2). Of these modifications, quartz is of greatest practical importance. Quartz has piezoelectric properties (cm. PIEZOELECTRIC MATERIALS), it is transparent to ultraviolet (UV) radiation. It is characterized by a very low coefficient of thermal expansion, so dishes made from quartz do not crack under temperature changes of up to 1000 degrees.
Quartz is chemically resistant to acids, but reacts with hydrofluoric acid:
SiO 2 + 6HF =H 2 + 2H 2 O
and hydrogen fluoride gas HF:
SiO 2 + 4HF = SiF 4 + 2H 2 O
These two reactions are widely used for glass etching.
When SiO 2 fuses with alkalis and basic oxides, as well as with carbonates of active metals, silicates are formed (cm. SILICATES)- salts of very weak water-insoluble silicic acids that do not have a constant composition (cm. SILICIC ACIDS) general formula xH 2 O ySiO 2 (quite often in the literature they write not very accurately not about silicic acids, but about silicic acid, although in fact they are talking about the same thing). For example, sodium orthosilicate can be obtained:
SiO 2 + 4NaOH = (2Na 2 O) SiO 2 + 2H 2 O,
calcium metasilicate:
SiO 2 + CaO = CaO SiO 2
or mixed calcium and sodium silicate:
Na 2 CO 3 + CaCO 3 + 6SiO 2 = Na 2 O CaO 6SiO 2 + 2CO 2
Window glass is made from Na 2 O·CaO·6SiO 2 silicate.
It should be noted that most silicates do not have a constant composition. Of all the silicates, only sodium and potassium silicates are soluble in water. Solutions of these silicates in water are called soluble glass. Due to hydrolysis, these solutions are characterized by a highly alkaline environment. Hydrolyzed silicates are characterized by the formation of not true, but colloidal solutions. When solutions of sodium or potassium silicates are acidified, a gelatinous white precipitate of hydrated silicic acids precipitates.
The main structural element of both solid silicon dioxide and all silicates is the group, in which the silicon atom Si is surrounded by a tetrahedron of four oxygen atoms O. In this case, each oxygen atom is connected to two silicon atoms. Fragments can be connected to each other in different ways. Among the silicates, according to the nature of the connections in their fragments, they are divided into island, chain, ribbon, layered, frame and others.
When SiO 2 is reduced by silicon at high temperatures, silicon monoxide of the composition SiO is formed.
Silicon is characterized by the formation of organosilicon compounds (cm. ORGANOSILONE COMPOUNDS), in which silicon atoms are connected in long chains due to bridging oxygen atoms -O-, and to each silicon atom, in addition to two O atoms, two more organic radicals R 1 and R 2 = CH 3, C 2 H 5, C 6 are attached H 5, CH 2 CH 2 CF 3, etc.
Application
Silicon is used as a semiconductor material. Quartz is used as a piezoelectric, as a material for the manufacture of heat-resistant chemical (quartz) cookware, and UV lamps. Silicates are widely used as building materials. Window glasses are amorphous silicates. Organosilicon materials are characterized by high wear resistance and are widely used in practice as silicone oils, adhesives, rubbers, and varnishes.
Biological role
For some organisms, silicon is an important biogenic element (cm. BIOGENIC ELEMENTS). It is part of the supporting structures in plants and skeletal structures in animals. Silicon is concentrated in large quantities by marine organisms - diatoms. (cm. DIATOM ALGAE), radiolarians (cm. RADIOLARIA), sponges (cm. SPONGS). Human muscle tissue contains (1-2)·10 -2% silicon, bone tissue - 17·10 -4%, blood - 3.9 mg/l. Up to 1 g of silicon enters the human body with food every day.
Silicon compounds are not poisonous. But inhalation of highly dispersed particles of both silicates and silicon dioxide, formed, for example, during blasting operations, when chiseling rocks in mines, during the operation of sandblasting machines, etc., is very dangerous. SiO 2 microparticles that enter the lungs crystallize in them, and the resulting crystals destroy the lung tissue and cause a serious illness - silicosis (cm. SILICOSIS). To prevent this dangerous dust from entering your lungs, you should use a respirator to protect your respiratory system.
encyclopedic Dictionary. 2009 .
Synonyms:See what “silicon” is in other dictionaries:
- (symbol Si), a widespread gray chemical element of group IV of the periodic table, non-metal. It was first isolated by Jens BERZELIUS in 1824. Silicon is found only in compounds such as SILICA (silicon dioxide) or in... ... Scientific and technical encyclopedic dictionary
Silicon- is produced almost exclusively by carbothermal reduction of silica using electric arc furnaces. It is a poor conductor of heat and electricity, harder than glass, usually in the form of a powder or more often shapeless pieces... ... Official terminology
SILICON- chem. element, non-metal, symbol Si (lat. Silicium), at. n. 14, at. m. 28.08; amorphous and crystalline silicon (which is built from the same type of crystals as diamond) are known. Amorphous K. brown powder with cubic structure in highly dispersed... ... Big Polytechnic Encyclopedia
- (Silicium), Si, chemical element of group IV of the periodic system, atomic number 14, atomic mass 28.0855; non-metal, melting point 1415°C. Silicon is the second most abundant element on Earth after oxygen, its content in the earth’s crust is 27.6% by weight.… … Modern encyclopedia
Si (lat. Silicium * a. silicium, silicon; n. Silizium; f. silicium; i. siliseo), chemical. element of group IV periodic. Mendeleev system, at. n. 14, at. m. 28,086. There are 3 stable isotopes found in nature: 28Si (92.27), 29Si (4.68%), 30Si (3 ... Geological encyclopedia
- (Si), synthetic monocrystal, semiconductor. Point symmetry group m3m, density 2.33 g/cm3, Tmelt=1417°C. Hardness on the Mohs scale 7, brittle, noticeable ductility. deformation begins at T>800°C. Thermally conductive, temperature coefficient. linear... ... Physical encyclopedia
Silicium Dictionary of Russian synonyms. silicon noun, number of synonyms: 6 leucon (1) mineral ... Synonym dictionary
Silicon- (Silicium), Si, chemical element of group IV of the periodic system, atomic number 14, atomic mass 28.0855; non-metal, melting point 1415°C. Silicon is the second most abundant element on Earth after oxygen, its content in the earth’s crust is 27.6% by weight.… … Illustrated Encyclopedic Dictionary
- (lat. Silicium) Si, chemical element of group IV of the periodic table, atomic number 14, atomic mass 28.0855. Dark gray crystals with a metallic luster; density 2.33 g/cm³, melting point 1415.C. Resistant to chemical influences. Makes up... ... Big Encyclopedic Dictionary
SILICON, silicon, many. no, husband (chem.). A chemical element found in most rocks. Ushakov's explanatory dictionary. D.N. Ushakov. 1935 1940 … Ushakov's Explanatory Dictionary
Silicon (Si) – stands in period 3, group IV of the main subgroup of the periodic system. Physical properties: silicon exists in two modifications: amorphous and crystalline. Amorphous silicon is a brown powder with a density of 2.33 g/cm3, soluble in metal melts. Crystalline silicon is dark gray crystals with a steely luster, hard and brittle, with a density of 2.4 g/cm3. Silicon consists of three isotopes: Si (28), Si (29), Si (30).
Chemical properties: electronic configuration: 1s22s22p63 s23p2 . Silicon is a non-metal. At the outer energy level, silicon has 4 electrons, which determines its oxidation states: +4, -4, -2. Valency – 2.4. Amorphous silicon has greater reactivity than crystalline silicon. Under normal conditions, it interacts with fluorine: Si + 2F2 = SiF4. At 1000 °C Si reacts with non-metals: CL2, N2, C, S.
Of the acids, silicon reacts only with a mixture of nitric and hydrofluoric acids:
It behaves differently in relation to metals: in molten Zn, Al, Sn, Pb it dissolves well, but does not react with them; Silicon interacts with other metal melts - with Mg, Cu, Fe - to form silicides: Si + 2Mg = Mg2Si. Silicon burns in oxygen: Si + O2 = SiO2 (sand).
Silicon dioxide or silica– stable connection Si, widely distributed in nature. It reacts by fusing it with alkalis and basic oxides, forming silicic acid salts - silicates. Receipt: In industry, silicon in its pure form is obtained by reducing silicon dioxide with coke in electric furnaces: SiO2 + 2C = Si + 2CO?.
In the laboratory, silicon is obtained by calcination of white sand with magnesium or aluminum:
SiO2 + 2Mg = 2MgO + Si.
3SiO2 + 4Al = Al2O3 + 3Si.
Silicon forms acids: H2 SiO3 – meta-silicic acid; H2 Si2O5 is dimethasilicic acid.
Finding in nature: quartz mineral – SiO2. Quartz crystals are shaped like a hexagonal prism, colorless and transparent, and are called rock crystal. Amethyst is a rock crystal colored purple with impurities; smoky topaz is brownish in color; agate and jasper are crystalline varieties of quartz. Amorphous silica is less common and exists in the form of the opal mineral – SiO2 nH2O. Diatomite, tripoli or diatomaceous earth (diatomaceous earth) are earthy forms of amorphous silicon.
42. The concept of colloidal solutions
Colloidal solutions– highly dispersed two-phase systems, consisting of a dispersion medium and a dispersed phase. The particle sizes are intermediate between true solutions, suspensions and emulsions. U colloidal particles molecular or ionic composition.
There are three types of internal structure of primary particles.
1. Suspensoids (or irreversible colloids)– heterogeneous systems, the properties of which can be determined by the developed interphase surface. Compared to suspensions, they are more highly dispersed. They cannot exist for a long time without a dispersion stabilizer. They are called irreversible colloids due to the fact that their sediments do not form sols again after evaporation. Their concentration is low - 0.1%. They differ slightly from the viscosity of the dispersed medium.
Suspensoids can be obtained:
1) methods of dispersion (crushing large bodies);
2) condensation methods (production of insoluble compounds using exchange reactions, hydrolysis, etc.).
The spontaneous decrease in dispersity in suspensions depends on the free surface energy. To obtain a long-lasting suspension, conditions are necessary to stabilize it.
Stable disperse systems:
1) dispersion medium;
2) dispersed phase;
3) stabilizer of the dispersed system.
The stabilizer can be ionic, molecular, but most often high-molecular.
Protective colloids– high-molecular compounds that are added for stabilization (proteins, peptides, polyvinyl alcohol, etc.).
2. Associative (or micellar colloids) – semicolloids that arise when there is a sufficient concentration of molecules consisting of hydrocarbon radicals (diphilic molecules) of low molecular weight substances when they associate into aggregates of molecules (micelles). Micelles are formed in aqueous solutions of detergents (soaps), organic dyes.
3. Molecular colloids (reversible or lyophilic colloids) – natural and synthetic high-molecular substances with high molecular weight. Their molecules have the size of colloidal particles (macromolecules).
Dilute solutions of colloids of high molecular weight compounds are homogeneous solutions. When highly diluted, these solutions obey the laws of dilute solutions.
Non-polar macromolecules dissolve in hydrocarbons, polar ones - in polar solvents.
Reversible colloids– substances, the dry residue of which, when adding a new portion of the solvent, goes back into solution.
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