Properties of silicon and its compounds. Silicon (chemical element): properties, characteristics, formula. History of the discovery of silicon

Mankind has known silicon for a long time. What is flint? This is a mineral that laid, in fact, the beginning of human civilization. There are references to the healing properties of silicon in the treatises of ancient scientists and philosophers.

Silicon then found application for wall decoration in buildings where meat and meat products were stored, for cutting out warts, for powdering wounds in the form of a powder, which made it possible to prevent gangrene; flint millstones produced flour with excellent taste and baking qualities.

From ancient times, people lined the inner surface and bottom of the wells with silicon, since it was noticed that the use of water from such wells ensured the prevention of somatic and infectious diseases, and the water turned out to be unusually tasty, clear and healing. The fact is that flint, in contact with water, changes its properties.

The healing properties of silicon and the causes of deficiency in the body

Clinical observations of modern scientists have proven that silicon in water produces silicic acid. Doses of this compound very small, but quite sufficient for silicic acid to dissolve salt deposits and slags, and also remove them from the body.

Water under the influence of silicon becomes "alive" and updated. Biologically active substances of silicon in our body, together with protein fractions, contribute to the formation of hormones, amino acids, enzymes; note that about 70 types of vitamins and minerals are not absorbed when the body lacks silicon.

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Causes of Silicon Deficiency

» Insufficient consumption of mineral water and fiber.

» Too much aluminum (usually seen in people who have cooked in aluminum cookware).

»Intensive body growth in childhood.

» Increased physical and mental stress every day.

What happens when there is a lack of silicon

» Progress for .

» In the kidneys, liver and gallbladder, there is a tendency to.

» The patient begins, and teeth, brittle nails.

» Eye diseases occur: in the elderly - farsightedness, glaucoma and cataracts, in children -.

» All blood vessels are affected with the development of early, increase.

» Due to a violation of the state of the connective tissue, periodontal disease occurs, deforming and.

Silicon is the source of good health

It is now known that silicon water increases the body's defenses, normalizes metabolism, prevents the occurrence of many diseases and helps to cure them, and slows down the aging of the body.

With the external use of silicon water, the skin is rejuvenated, the condition and growth of hair improves, wrinkles disappear, the color of the hands and face improves.

How to drink silicon water. It can be used without restrictions. Usually silicon water is drunk from one to three glasses at room temperature, but you need to drink in small sips. As noted above, silicon changes the properties of water when in contact with it.

Activated silica water has a detrimental effect on pathogenic microorganisms, reduces the growth of bacteria that contribute to fermentation and decay. At the same time, the water becomes pleasant to the taste and perfectly clean, for a long time it does not deteriorate, acquiring many other medicinal properties. Silicon displaces salts of heavy and harmful metals, they settle to the bottom, and pure water remains on top.

Everyone knows how much water is necessary for the human body. It contains about 70% water and it is impossible to imagine life without it. Given that all metabolic processes occur in the presence of an aqueous medium, it can be said with certainty that it is water that plays the role of a conductor of a large number of physiological processes, without which the vital activity of cells and tissues is impossible.

How to prepare silicon water

It is recommended to infuse silicon in enameled or glassware. Personally, I prepare silicon water at home in a three-liter glass jar. I put silicon pebbles in a jar, pour clean well water (if you live in a city, it is better to filter it through a regular home filter before that).

I put the jar in a room where direct sunlight does not fall and cover it with an ordinary gauze napkin (a piece of gauze) to ensure free gas exchange. Silicon water, used for making tea, food or infusions of medicinal plants, insist two or three days. In this case, the following requirements must be observed:

1. After each draining of the water, the silicon and the container are thoroughly rinsed with running water.
2. The sediment remaining at the bottom must be poured into the sink.
3. It is allowed to boil water infused with flint, but not the flint itself, because in this case the water is oversaturated with biologically active substances. Such water can only be used externally.
4. It is not recommended to store water in the refrigerator together with silicon.
5. It has been established that silicon water retains its healing properties for several months.
6. After repeated use (3-5 times), silicon should be washed under running water and exposed to fresh air for 2 hours for ventilation.
7. After a certain time, deposits or layers may appear on the surface of the minerals. In this case, the pebbles should be placed for two hours in salted water or a 2% solution of acetic acid, and then rinsed with running water. Then lower the stones again for two hours in a solution of baking soda and rinse again under the tap.
8. After 8-12 months, it is desirable to split the stones in order to strengthen (renew) their properties, but it is better to acquire a new mineral.
9. Silicon infusion is carried out at room temperature.

Be healthy, my dear readers. God bless you!

Silicon

SILICON-I; m.[from Greek. krēmnos - cliff, rock] A chemical element (Si), dark gray crystals with a metallic sheen, which are part of most rocks.

◁ Silicon, th, th. K salts. Siliceous (see 2.K .; 1 sign).

(lat. Silicium), a chemical element of group IV of the periodic system. Dark gray crystals with a metallic sheen; density 2.33 g / cm 3, t pl 1415ºC. Resistant to chemical attack. It makes up 27.6% of the mass of the earth's crust (2nd place among the 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).

SILICON (lat. Silicium from silex - flint), Si (read "silicium", but now 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 is 92.27% by mass in it), 29 (4.68%) and 30 (3.05%). Configuration of the outer electron layer of a neutral unexcited silicon atom 3 s 2 R 2 . In compounds, it usually exhibits an oxidation state of +4 (valency IV) and very rarely +3, +2 and +1 (valencies III, II and I, respectively). In the periodic system of Mendeleev, silicon is located in the IVA group (in the carbon group), in the third period.
The radius of the neutral silicon atom is 0.133 nm. Sequential ionization energies of silicon atom are 8.1517, 16.342, 33.46 and 45.13 eV, 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. On the Pauling scale, the electronegativity of silicon is 1.9. Although silicon is usually classified as a non-metal, it occupies an intermediate position between metals and non-metals in a number of properties.
In free form - brown powder or light gray compact material with a metallic sheen.
Discovery history
Silicon compounds have been known to man since time immemorial. But with a simple substance silicon man met only about 200 years ago. In fact, the first researchers who received 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 metallic potassium leads to the formation of a brownish-brown substance:
SiF 4 + 4K = Si + 4KF, however, the researchers themselves did not make 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 the composition K 2 SiF 6 with metallic potassium to obtain silicon. He received 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. St. Clair Deville (cm. SAINT CLAIR DEVILLE Henri Etienne) .
Being in nature
In terms of prevalence 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 part of several hundred different natural silicates (cm. SILICATES) and aluminosilicates (cm. ALUMOSILICATES). Silica, or silicon dioxide, is also widely distributed (cm. SILICON DIOXIDE) SiO 2 (river sand (cm. SAND), quartz (cm. QUARTZ), flint (cm. FLINT) and others), which makes up about 12% of the earth's crust (by mass). Silicon is not found in free form in nature.
Receipt
In industry, silicon is obtained by reducing the SiO 2 melt with coke at a temperature of about 1800°C in arc furnaces. The purity of the silicon thus obtained is about 99.9%. Since silicon of a 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 by various methods from impurities and, at the final stage, are reduced with pure hydrogen. It is also possible to purify silicon by preliminary obtaining magnesium silicide Mg 2 Si. Further, volatile monosilane SiH 4 is obtained from magnesium silicide using hydrochloric or acetic acid. Monosilane is further purified by distillation, sorption, and other methods, and then decomposed into silicon and hydrogen at a temperature of about 1000°C. The content of impurities in the silicon obtained by these methods is reduced to 10 -8 -10 -6% by weight.
Physical and chemical properties
The crystal lattice of silicon is a cubic face-centered type of diamond, parameter a = 0.54307 nm (other polymorphic modifications of silicon were also obtained at high pressures), but due to the longer bond length between Si-Si atoms compared to the C-C bond length, the hardness of silicon is much less than that of diamond.
The density of silicon is 2.33 kg/dm 3 . Melting point 1410°C, boiling point 2355°C. Silicon is brittle, only when heated above 800°C does it become plastic. 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 affected by the microimpurities contained in it. To obtain single crystals of silicon with hole conductivity, additives of elements of the III group - boron are introduced into silicon (cm. BOR (chemical element)), aluminum (cm. ALUMINUM), gallium (cm. GALLIUM) and india (cm. INDIUM), with electronic conductivity - additives of elements of the V-th group - phosphorus (cm. PHOSPHORUS), arsenic (cm. ARSENIC) or antimony (cm. ANTIMONY). The electrical properties of silicon can be varied by changing the conditions for processing single crystals, in particular, by treating the silicon surface with various chemical agents.
Chemically, silicon is inactive. At room temperature, it reacts only with gaseous fluorine to form 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 volatile tetrahalides SiHal 4 .
Silicon does not directly react with hydrogen, silicon compounds with hydrogen are silanes (cm. SILANES) with the general formula Si n H 2n+2 - obtained indirectly. Monosilane SiH 4 (it is often called simply silane) is released during the interaction of metal silicides with acid solutions, for example:
Ca 2 Si + 4HCl \u003d 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 nitride Si 3 N 4 , with boron - thermally and chemically stable borides SiB 3 , SiB 6 and SiB 12 . The 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 activity. Carborundum is widely used as an abrasive material.
When silicon is heated with metals, silicides are formed (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 (transition metal silicides). Silicides of active metals decompose under the action of acids, silicides of transition metals are chemically stable and do not decompose under the action of acids. Metal-like silicides have high melting points (up to 2000°C). Metal-like silicides of compositions MSi, M 3 Si 2 , M 2 Si 3 , M 5 Si 3 , and MSi 2 are formed most frequently. Metal-like silicides are chemically inert, 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 polymorphic modifications (quartz (cm. QUARTZ), tridymite, cristobalite, glassy SiO 2). Of these modifications, quartz has the greatest practical value. 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 the dishes made of quartz do not crack at temperature drops of up to 1000 degrees.
Quartz is chemically resistant to acids, but reacts with hydrofluoric acid:
SiO 2 + 6HF \u003d H 2 + 2H 2 O
and gaseous hydrogen fluoride HF:
SiO 2 + 4HF \u003d SiF 4 + 2H 2 O
These two reactions are widely used for glass etching.
When SiO 2 is fused 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. SILICON ACIDS) the general formula xH 2 O ySiO 2 (quite often in the literature they do not write very accurately not about silicic acids, but about silicic acid, although in fact we are talking about the same thing). For example, sodium orthosilicate can be obtained:
SiO 2 + 4NaOH \u003d (2Na 2 O) SiO 2 + 2H 2 O,
calcium metasilicate:
SiO 2 + CaO \u003d 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 strongly alkaline environment. Hydrolyzed silicates are characterized by the formation of not true, but colloidal solutions. When acidifying solutions of sodium or potassium silicates, 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 linked to each other in different ways. Among the silicates, according to the nature of the bonds in them, the fragments are divided into island, chain, ribbon, layered, framework, and others.
When SiO 2 is reduced with silicon at high temperatures, silicon monoxide of the composition SiO is formed.
Silicon is characterized by the formation of organosilicon compounds (cm. SILICON COMPOUNDS), in which silicon atoms are connected in long chains due to bridging oxygen atoms -O-, and to each silicon atom, except for two O atoms, two more organic radicals R 1 and R 2 \u003d CH 3, C 2 H 5, C 6 are attached H 5 , CH 2 CH 2 CF 3 and others.
Application
Silicon is used as a semiconductor material. Quartz is used as a piezoelectric material, as a material for the manufacture of heat-resistant chemical (quartz) dishes, and UV radiation lamps. Silicates are widely used as building materials. Window panes are amorphous silicates. Silicone 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. In large quantities, silicon is concentrated by marine organisms - diatoms. (cm. DIATOM ALGAE), radiolarians (cm. RADIOLARIA), sponges (cm. SPONGE). Human muscle tissue contains (1-2) 10 -2% silicon, bone tissue - 17 10 -4%, blood - 3.9 mg / l. With food, up to 1 g of silicon enters the human body daily.
Silicon compounds are not poisonous. But it is very dangerous to inhale highly dispersed particles of both silicates and silicon dioxide, which are formed, for example, during blasting, when chiseling rocks in mines, during the operation of sandblasting machines, etc. 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 the lungs, a respirator should be used for respiratory protection.

encyclopedic Dictionary. 2009 .

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 obtained almost exclusively by carbothermal reduction of silicon dioxide 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 crystals of the same type as diamond) are known. Amorphous K. brown powder of a cubic structure in a highly dispersed ... ... Great Polytechnic Encyclopedia

- (Silicium), Si, a chemical element of group IV of the periodic system, atomic number 14, atomic mass 28.0855; non-metal, mp 1415shC. Silicon is the second most abundant element on Earth after oxygen, the content in the earth's crust is 27.6% by mass. ... ... Modern Encyclopedia

Si (lat. Silicium * a. silicium, silicon; n. Silizium; f. silicium; and. siliseo), chem. element IV group periodic. Mendeleev systems, at. n. 14, at. m. 28.086. In nature, there are 3 stable isotopes 28Si (92.27), 29Si (4.68%), 30Si (3 ... Geological Encyclopedia

Element characteristic

14 Si 1s 2 2s 2 2p 6 3s 2 3p 2

Isotopes: 28 Si (92.27%); 29Si (4.68%); 30 Si (3.05%)

Silicon is the second most abundant element in the earth's crust after oxygen (27.6% by mass). It does not occur in nature in a free state, it is found mainly in the form of SiO 2 or silicates.

Si compounds are toxic; inhalation of the smallest particles of SiO 2 and other silicon compounds (for example, asbestos) causes a dangerous disease - silicosis

In the ground state, the silicon atom has a valence = II, and in an excited state = IV.

The most stable oxidation state of Si is +4. In compounds with metals (silicides), S.O. -four.

Methods for obtaining silicon

The most common natural silicon compound is silica (silicon dioxide) SiO 2 . It is the main raw material for the production of silicon.

1) Recovery of SiO 2 with carbon in arc furnaces at 1800 "C: SiO 2 + 2C \u003d Si + 2CO

2) High-purity Si from a technical product is obtained according to the scheme:

a) Si → SiCl 2 → Si

b) Si → Mg 2 Si → SiH 4 → Si

Physical properties of silicon. Allotropic modifications of silicon

1) Crystalline silicon - a substance of silver-gray color with a metallic sheen, a diamond-type crystal lattice; m.p. 1415 "C, b.p. 3249" C, density 2.33 g/cm3; is a semiconductor.

2) Amorphous silicon - brown powder.

Chemical properties of silicon

In most reactions, Si acts as a reducing agent:

At low temperatures, silicon is chemically inert; when heated, its reactivity sharply increases.

1. It interacts with oxygen at T above 400°C:

Si + O 2 \u003d SiO 2 silicon oxide

2. Reacts with fluorine already at room temperature:

Si + 2F 2 = SiF 4 silicon tetrafluoride

3. Reactions with other halogens proceed at a temperature = 300 - 500 ° C

Si + 2Hal 2 = SiHal 4

4. With sulfur vapor at 600 ° C forms a disulfide:

5. Reaction with nitrogen occurs above 1000°C:

3Si + 2N 2 = Si 3 N 4 silicon nitride

6. At a temperature = 1150°С it reacts with carbon:

SiO 2 + 3C \u003d SiC + 2CO

Carborundum is close to diamond in hardness.

7. Silicon does not directly react with hydrogen.

8. Silicon is resistant to acids. Interacts only with a mixture of nitric and hydrofluoric (hydrofluoric) acids:

3Si + 12HF + 4HNO 3 = 3SiF 4 + 4NO + 8H 2 O

9. reacts with alkali solutions to form silicates and release hydrogen:

Si + 2NaOH + H 2 O \u003d Na 2 SiO 3 + 2H 2

10. The reducing properties of silicon are used to isolate metals from their oxides:

2MgO \u003d Si \u003d 2Mg + SiO 2

In reactions with metals, Si is an oxidizing agent:

Silicon forms silicides with s-metals and most d-metals.

The composition of silicides of this metal can be different. (For example, FeSi and FeSi 2; Ni 2 Si and NiSi 2.) One of the most famous silicides is magnesium silicide, which can be obtained by direct interaction of simple substances:

2Mg + Si = Mg 2 Si

Silane (monosilane) SiH 4

Silanes (silicon hydrogens) Si n H 2n + 2, (compare with alkanes), where n \u003d 1-8. Silanes - analogues of alkanes, differ from them in the instability of -Si-Si- chains.

Monosilane SiH 4 is a colorless gas with an unpleasant odor; soluble in ethanol, gasoline.

Ways to get:

1. Decomposition of magnesium silicide with hydrochloric acid: Mg 2 Si + 4HCI = 2MgCI 2 + SiH 4

2. Reduction of Si halides with lithium aluminum hydride: SiCl 4 + LiAlH 4 = SiH 4 + LiCl + AlCl 3

Chemical properties.

Silane is a strong reducing agent.

1.SiH 4 is oxidized by oxygen even at very low temperatures:

SiH 4 + 2O 2 \u003d SiO 2 + 2H 2 O

2. SiH 4 is easily hydrolyzed, especially in an alkaline environment:

SiH 4 + 2H 2 O \u003d SiO 2 + 4H 2

SiH 4 + 2NaOH + H 2 O \u003d Na 2 SiO 3 + 4H 2

Silicon (IV) oxide (silica) SiO 2

Silica exists in various forms: crystalline, amorphous and glassy. The most common crystalline form is quartz. When quartz rocks are destroyed, quartz sands are formed. Quartz single crystals are transparent, colorless (rock crystal) or colored with impurities in various colors (amethyst, agate, jasper, etc.).

Amorphous SiO 2 occurs in the form of the mineral opal: silica gel is artificially obtained, consisting of colloidal SiO 2 particles and being a very good adsorbent. Glassy SiO 2 is known as quartz glass.

Physical properties

In water, SiO 2 dissolves very slightly, in organic solvents it also practically does not dissolve. Silica is a dielectric.

Chemical properties

1. SiO 2 is an acid oxide, therefore amorphous silica slowly dissolves in aqueous solutions of alkalis:

SiO 2 + 2NaOH \u003d Na 2 SiO 3 + H 2 O

2. SiO 2 also interacts when heated with basic oxides:

SiO 2 + K 2 O \u003d K 2 SiO 3;

SiO 2 + CaO \u003d CaSiO 3

3. Being a non-volatile oxide, SiO 2 displaces carbon dioxide from Na 2 CO 3 (during fusion):

SiO 2 + Na 2 CO 3 \u003d Na 2 SiO 3 + CO 2

4. Silica reacts with hydrofluoric acid, forming hydrofluorosilicic acid H 2 SiF 6:

SiO 2 + 6HF \u003d H 2 SiF 6 + 2H 2 O

5. At 250 - 400 ° C, SiO 2 interacts with gaseous HF and F 2, forming tetrafluorosilane (silicon tetrafluoride):

SiO 2 + 4HF (gas.) \u003d SiF 4 + 2H 2 O

SiO 2 + 2F 2 \u003d SiF 4 + O 2

Silicic acids

Known:

Orthosilicic acid H 4 SiO 4 ;

Metasilicic (silicic) acid H 2 SiO 3 ;

Di- and polysilicic acids.

All silicic acids are sparingly soluble in water and easily form colloidal solutions.

Ways to receive

1. Precipitation by acids from solutions of alkali metal silicates:

Na 2 SiO 3 + 2HCl \u003d H 2 SiO 3 ↓ + 2NaCl

2. Hydrolysis of chlorosilanes: SiCl 4 + 4H 2 O \u003d H 4 SiO 4 + 4HCl

Chemical properties

Silicic acids are very weak acids (weaker than carbonic acid).

When heated, they dehydrate to form silica as the end product.

H 4 SiO 4 → H 2 SiO 3 → SiO 2

Silicates - salts of silicic acids

Since silicic acids are extremely weak, their salts in aqueous solutions are highly hydrolyzed:

Na 2 SiO 3 + H 2 O \u003d NaHSiO 3 + NaOH

SiO 3 2- + H 2 O \u003d HSiO 3 - + OH - (alkaline medium)

For the same reason, when carbon dioxide is passed through silicate solutions, silicic acid is displaced from them:

K 2 SiO 3 + CO 2 + H 2 O \u003d H 2 SiO 3 ↓ + K 2 CO 3

SiO 3 + CO 2 + H 2 O \u003d H 2 SiO 3 ↓ + CO 3

This reaction can be considered as a qualitative reaction for silicate ions.

Among the silicates, only Na 2 SiO 3 and K 2 SiO 3 are highly soluble, which are called soluble glass, and their aqueous solutions are called liquid glass.

Glass

Ordinary window glass has the composition Na 2 O CaO 6SiO 2, i.e. it is a mixture of sodium and calcium silicates. It is obtained by fusing soda Na 2 CO 3 , CaCO 3 limestone and SiO 2 sand;

Na 2 CO 3 + CaCO 3 + 6SiO 2 \u003d Na 2 O CaO 6SiO 2 + 2CO 2

Cement

A powdered binder material that, when interacting with water, forms a plastic mass, which eventually turns into a solid stone-like body; main building material.

The chemical composition of the most common Portland cement (in% by weight) - 20 - 23% SiO 2; 62 - 76% CaO; 4 - 7% Al 2 O 3; 2-5% Fe 2 O 3 ; 1-5% MgO.

Silicon- a very rare mineral species from the class of native elements. In fact, it is surprising how rarely the chemical element silicon, which in a bound form is at least 27.6% of the mass of the earth's crust, occurs in nature in its pure form. But silicon binds strongly with oxygen and is almost always in the form of silica - silicon dioxide, SiO 2 (quartz family) or as part of silicates (SiO 4 4-). Native silicon as a mineral was found in the products of volcanic fumes and as the smallest inclusions in native gold.

See also:

STRUCTURE

PROPERTIES

Silicon is brittle, only when heated above 800 °C does it become plastic. It is transparent to infrared radiation from a wavelength of 1.1 µm. Own concentration of charge carriers - 5.81 10 15 m −3 (for a temperature of 300 K). Melting point 1415 ° C, boiling point 2680 ° C, density 2.33 g / cm 3. It has semiconductor properties, its resistance decreases with increasing temperature.

Amorphous silicon is a brown powder based on a highly disordered diamond-like structure. It is more reactive than crystalline silicon.

MORPHOLOGY

Isolated facts of finding pure silicon in native form are noted.

ORIGIN

The content of silicon in the earth's crust is, according to various sources, 27.6-29.5% by weight. Thus, in terms of prevalence in the earth's crust, silicon ranks second after oxygen. Concentration in sea water 3 mg/l. Isolated facts of finding pure silicon in native form are noted - the smallest inclusions (nanoindividuals) in ijolites of the Goryachegorsk alkaline-gabbroid massif (Kuznetsk Alatau, Krasnoyarsk Territory); in Karelia and on the Kola Peninsula (based on the study of the Kola superdeep well); microscopic crystals in the fumaroles of Tolbachik and Kudryavy volcanoes (Kamchatka).

APPLICATION

Monocrystalline silicon - in addition to electronics and solar energy, is used to make mirrors for gas lasers.

Compounds of metals with silicon - silicides - are widely used in industry (for example, electronic and atomic) materials with a wide range of useful chemical, electrical and nuclear properties (resistance to oxidation, neutrons, etc.). Silicides of a number of elements are important thermoelectric materials.

Silicon compounds serve as the basis for the production of glass and cement. The silicate industry is engaged in the production of glass and cement. It also produces silicate ceramics - brick, porcelain, faience and products from them. Silicate glue is widely known, used in construction as a desiccant, and in pyrotechnics and in everyday life for gluing paper. Silicone oils and silicones, materials based on organosilicon compounds, have become widespread.

Technical silicon finds the following applications:

• raw materials for metallurgical industries: alloy component (bronze, silumin);
• deoxidizer (when smelting iron and steel);
• a modifier of metal properties or an alloying element (for example, the addition of a certain amount of silicon in the production of transformer steels reduces the coercive force of the finished product), etc.;
• raw materials for the production of purer polycrystalline silicon and purified metallurgical silicon (in the literature "umg-Si");
• raw materials for the production of organic silicon materials, silanes;
• sometimes technical grade silicon and its alloy with iron (ferrosilicon) are used to produce hydrogen in the field;
• for the production of solar panels;
• anti-block (release agent) in the plastics industry.

Silicon (eng. Silicon) - Si

CLASSIFICATION

Many modern technological devices and devices were created due to the unique properties of substances found in nature. Mankind, by experimentation and careful study of the elements around us, is constantly modernizing its own inventions - this process is called technical progress. It is based on elementary, accessible to everyone things that surround us in everyday life. For example, sand: what can be surprising and unusual in it? Scientists were able to isolate silicon from it - a chemical element without which computer technology would not exist. The scope of its application is diverse and constantly expanding. This is achieved due to the unique properties of the silicon atom, its structure and the possibility of compounds with other simple substances.

Characteristic

In the one developed by D. I. Mendeleev, silicon is designated by the symbol Si. It belongs to non-metals, is located in the main fourth group of the third period, has atomic number 14. Its proximity to carbon is not accidental: in many respects their properties are comparable. It does not occur in nature in its pure form, as it is an active element and has fairly strong bonds with oxygen. The main substance is silica, which is an oxide, and silicates (sand). At the same time, silicon (its natural compounds) is one of the most common chemical elements on Earth. In terms of mass fraction of content, it ranks second after oxygen (more than 28%). The top layer of the earth's crust contains silicon dioxide (this is quartz), various types of clays and sand. The second most common group is its silicates. At a depth of about 35 km from the surface, there are layers of granite and basalt deposits, which include siliceous compounds. The percentage of content in the earth's core has not yet been calculated, but the layers of the mantle closest to the surface (up to 900 km) contain silicates. In the composition of sea water, the concentration of silicon is 3 mg / l, 40% consists of its compounds. The expanses of space that mankind has studied to date contain this chemical element in large quantities. For example, meteorites that approached the Earth at a distance accessible to researchers showed that they consist of 20% silicon. There is a possibility of the formation of life based on this element in our galaxy.

Research process

The history of the discovery of the chemical element silicon has several stages. Many substances systematized by Mendeleev have been used by mankind for centuries. At the same time, the elements were in their natural form, i.e. in compounds that were not subjected to chemical processing, and all their properties were not known to people. In the process of studying all the features of the substance, new directions of use appeared for it. The properties of silicon have not been fully studied to date - this element, with a fairly wide and varied range of applications, leaves room for new discoveries for future generations of scientists. Modern technologies will significantly speed up this process. In the 19th century, many famous chemists tried to obtain pure silicon. For the first time, L. Tenar and J. Gay-Lussac managed to do this in 1811, but the discovery of the element belongs to J. Berzelius, who was able not only to isolate the substance, but also to describe it. A Swedish chemist obtained silicon in 1823 using potassium metal and potassium salt. The reaction took place with a catalyst in the form of high temperature. The obtained simple gray-brown substance was amorphous silicon. The crystalline pure element was obtained in 1855 by St. Clair Deville. The complexity of isolation is directly related to the high strength of atomic bonds. In both cases, the chemical reaction is aimed at the process of purification from impurities, while the amorphous and crystalline models have different properties.

Silicon pronunciation of the chemical element

The first name of the resulting powder - kisel - was proposed by Berzelius. In the UK and the US, silicon is still called nothing more than silicon (Silicium) or silicone (Silicon). The term comes from the Latin "flint" (or "stone"), and in most cases it is tied to the concept of "earth" due to its wide distribution in nature. The Russian pronunciation of this chemical is different, it all depends on the source. It was called silica (Zakharov used this term in 1810), sicily (1824, Dvigubsky, Solovyov), silica (1825, Strakhov), and only in 1834 did the Russian chemist German Ivanovich Hess introduce the name that is still used today. in most sources - silicon. In it is denoted by the symbol Si. How is the chemical element silicon read? Many scientists in English-speaking countries pronounce its name as "si" or use the word "silicone". From here comes the world-famous name of the valley, which is a research and production site for computer technology. The Russian-speaking population calls the element silicon (from the ancient Greek word for "rock, mountain").

Finding in nature: deposits

Entire mountain systems are composed of silicon compounds, which are not found in their pure form, because all known minerals are dioxides or silicates (aluminosilicates). Amazingly beautiful stones are used by people as an ornamental material - these are opals, amethysts, quartz of various types, jasper, chalcedony, agate, rock crystal, carnelian and many others. They were formed due to the inclusion of various substances in the composition of silicon, which determined their density, structure, color and direction of use. The entire inorganic world can be associated with this chemical element, which in the natural environment forms strong bonds with metals and non-metals (zinc, magnesium, calcium, manganese, titanium, etc.). Compared to other substances, silicon is readily available for mining on an industrial scale: it is found in most types of ores and minerals. Therefore, actively developed deposits are tied to available energy sources rather than to territorial accumulations of matter. Quartzites and quartz sands are found in all countries of the world. The largest manufacturers and suppliers of silicon are: China, Norway, France, USA (West Virginia, Ohio, Alabama, New York), Australia, South Africa, Canada, Brazil. All manufacturers use different methods, which depend on the type of product being manufactured (technical, semiconductor, high-frequency silicon). A chemical element, additionally enriched or, conversely, purified from all types of impurities, has individual properties on which its further use depends. This also applies to this substance. The structure of silicon determines the scope of its application.

Usage history

Very often, due to the similarity of names, people confuse silicon and flint, but these concepts are not identical. Let's bring clarity. As already mentioned, silicon in its pure form does not occur in nature, which cannot be said about its compounds (the same silica). The main minerals and rocks formed by the dioxide of the substance we are considering are sand (river and quartz), quartz and quartzites, and flint. Everyone must have heard about the latter, because it is given great importance in the history of the development of mankind. The first tools created by people during the Stone Age are associated with this stone. Its sharp edges, formed when breaking off from the main rock, greatly facilitated the work of ancient housewives, and the possibility of sharpening - hunters and fishermen. Flint did not have the strength of metal products, but failed tools were easy to replace with new ones. Its use as a flint and steel continued for many centuries - until the invention of alternative sources.

As for modern realities, the properties of silicon make it possible to use the substance for interior decoration or the creation of ceramic dishes, while, in addition to a beautiful aesthetic appearance, it has many excellent functional qualities. A separate direction of its application is associated with the invention of glass about 3000 years ago. This event made it possible to create mirrors, dishes, mosaic stained-glass windows from compounds containing silicon. The formula of the initial substance was supplemented with the necessary components, which made it possible to give the product the required color and influenced the strength of the glass. Works of art of amazing beauty and variety were made by man from minerals and stones containing silicon. The healing properties of this element were described by ancient scientists and have been used throughout the history of mankind. They laid out wells for drinking water, pantries for storing food, used both in everyday life and in medicine. The powder obtained as a result of grinding was applied to wounds. Particular attention was paid to water, which was infused in dishes made from compounds containing silicon. The chemical element interacted with its composition, which made it possible to destroy a number of pathogenic bacteria and microorganisms. And this is far from all the industries where the substance we are considering is very, very in demand. The structure of silicon determines its versatility.

Properties

For a more detailed acquaintance with the features of a substance, it must be considered taking into account all possible properties. The plan for characterizing the chemical element of silicon includes physical properties, electrophysical indicators, the study of compounds, reactions and conditions for their passage, etc. Silicon in crystalline form has a dark gray color with a metallic sheen. The face-centered cubic lattice is similar to the carbon one (diamond), but due to the longer bonds, it is not so strong. Heating up to 800 ° C makes it plastic, in other cases it remains brittle. The physical properties of silicon make this substance truly unique: it is transparent to infrared radiation. Melting point - 1410 0 C, boiling point - 2600 0 C, density under normal conditions - 2330 kg / m 3. The thermal conductivity is not constant, for various samples it is taken at an approximate value of 25 0 C. The properties of the silicon atom make it possible to use it as a semiconductor. This direction of application is most in demand in the modern world. The magnitude of the electrical conductivity is influenced by the composition of silicon and the elements that are in combination with it. So, for increased electronic conductivity, antimony, arsenic, phosphorus are used, for perforated - aluminum, gallium, boron, indium. When creating devices with silicon as a conductor, surface treatment with a certain agent is used, which affects the operation of the device.

The properties of silicon as an excellent conductor are widely used in modern instrumentation. Its use in the production of complex equipment (for example, modern computing devices, computers) is especially relevant.

Silicon: characteristics of a chemical element

In most cases, silicon is tetravalent, there are also bonds in which it can have a value of +2. Under normal conditions, it is inactive, has strong compounds, and at room temperature can react only with fluorine, which is in a gaseous state of aggregation. This is due to the effect of blocking the surface with a dioxide film, which is observed when interacting with ambient oxygen or water. To stimulate reactions, a catalyst must be used: raising the temperature is ideal for a substance such as silicon. The chemical element interacts with oxygen at 400-500 0 C, as a result, the dioxide film increases, and the oxidation process takes place. When the temperature rises to 50 0 C, a reaction with bromine, chlorine, iodine is observed, resulting in the formation of volatile tetrahalides. Silicon does not interact with acids, with the exception of a mixture of hydrofluoric and nitric acids, while any alkali in a heated state is a solvent. Silicon hydrogens are formed only by the decomposition of silicides; it does not react with hydrogen. Compounds with boron and carbon are distinguished by the greatest strength and chemical passivity. High resistance to alkalis and acids has a connection with nitrogen, which occurs at temperatures above 1000 0 C. Silicides are obtained by reaction with metals, and in this case, the valency shown by silicon depends on the additional element. The formula of the substance formed with the participation of the transition metal is resistant to acids. The structure of the silicon atom directly affects its properties and ability to interact with other elements. The process of formation of bonds in nature and under the influence on a substance (in laboratory, industrial conditions) differs significantly. The structure of silicon suggests its chemical activity.

Structure

Silicon has its own characteristics. The charge of the nucleus is +14, which corresponds to the serial number in the periodic system. Number of charged particles: protons - 14; electrons - 14; neutrons - 14. The scheme of the structure of the silicon atom has the following form: Si +14) 2) 8) 4. There are 4 electrons at the last (external) level, which determines the degree of oxidation with the “+” or “-” sign. Silicon oxide has the formula SiO 2 (valence 4+), the volatile hydrogen compound is SiH 4 (valence -4). The large volume of the silicon atom makes it possible in some compounds to have a coordination number of 6, for example, when combined with fluorine. Molar mass - 28, atomic radius - 132 pm, electron shell configuration: 1S 2 2S 2 2P 6 3S 2 3P 2.

Application

Surface or fully doped silicon is used as a semiconductor in the creation of many, including high-precision, devices (for example, solar photocells, transistors, current rectifiers, etc.). Ultra-pure silicon is used to create solar cells (energy). The single-crystal type is used to make mirrors and a gas laser. From silicon compounds, glass, ceramic tiles, dishes, porcelain, faience are obtained. It is difficult to describe the variety of types of goods received, their operation takes place at the household level, in art and science, and in production. The resulting cement serves as a raw material for the creation of building mixtures and bricks, finishing materials. The distribution of oils, based on lubricants, can significantly reduce the friction force in the moving parts of many mechanisms. Silicides are widely used in industry due to their unique properties in the field of resistance to aggressive media (acids, temperatures). Their electrical, nuclear and chemical characteristics are taken into account by specialists in complex industries, and the structure of the silicon atom also plays an important role.

We have listed the most knowledge-intensive and advanced areas of application to date. The most common, commercial silicon produced in large volumes is used in a number of areas:

1. As a raw material for the production of a purer substance.
2. For alloying alloys in the metallurgical industry: the presence of silicon increases refractoriness, increases corrosion resistance and mechanical strength (with an excess of this element, the alloy may be too brittle).
3. As a deoxidizer to remove excess oxygen from metal.
4. Raw materials for the production of silanes (silicon compounds with organic substances).
5. For the production of hydrogen from an alloy of silicon with iron.
6. Manufacturing of solar panels.

The value of this substance is also great for the normal functioning of the human body. The structure of silicon, its properties are decisive in this case. At the same time, an excess or lack of it leads to serious diseases.

In the human body

Medicine has long used silicon as a bactericidal and antiseptic agent. But with all the benefits of external use, this element must be constantly renewed in the human body. A normal level of its content will improve life in general. In case of its deficiency, more than 70 trace elements and vitamins will not be absorbed by the body, which will significantly reduce resistance to a number of diseases. The highest percentage of silicon is observed in bones, skin, tendons. It plays the role of a structural element that maintains strength and gives elasticity. All skeletal hard tissues are formed by its compounds. As a result of recent studies, silicon content was found in the kidneys, pancreas and connective tissues. The role of these organs in the functioning of the body is quite large, so a decrease in its content will have a detrimental effect on many basic indicators of life support. The body should receive 1 gram of silicon per day with food and water - this will help to avoid possible diseases, such as inflammation of the skin, softening of the bones, the formation of stones in the liver, kidneys, visual impairment, hair and nails, atherosclerosis. With a sufficient level of this element, immunity increases, metabolic processes normalize, and the assimilation of many elements necessary for human health improves. The largest amount of silicon is in cereals, radish, buckwheat. Silicon water will bring significant benefits. To determine the amount and frequency of its use, it is better to consult a specialist.