Element characteristic

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

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

Silicon is the second most abundant element in the earth's crust after oxygen (27.6% by weight). It does not occur in the free state in nature, 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 valence = II, and in the excited state = IV.

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

Silicon production methods

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

1) Reduction of SiO 2 with carbon in arc furnaces at 1800 "C: SiO 2 + 2C = 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 is a silvery-gray substance with a metallic luster, a diamond-type crystal lattice; t. pl. 1415 "C, bp 3249" C, density 2.33 g / cc; is a semiconductor.

2) Amorphous silicon is a brown powder.

Silicon chemical properties

In most reactions, Si acts as a reducing agent:

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

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

Si + O 2 = SiO 2 silicon oxide

2.Reacts with fluorine already at room temperature:

Si + 2F 2 = SiF 4 silicon tetrafluoride

3.With the rest of the halogens, reactions take place at a temperature of = 300 - 500 ° С

Si + 2Hal 2 = SiHal 4

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

5. The reaction with nitrogen occurs above 1000 ° C:

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

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

SiO 2 + 3C = 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 = Na 2 SiO 3 + 2H 2

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

2MgO = Si = 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 the 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 (silicas) Si n H 2n + 2, (compare with alkanes), where n = 1-8. Silanes are analogs of alkanes, differing from them in the instability of the -Si-Si- chains.

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

Methods of obtaining:

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 powerful reducing agent.

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

SiH 4 + 2O 2 = SiO 2 + 2H 2 O

2. SiH 4 readily hydrolyzes, especially in an alkaline environment:

SiH 4 + 2H 2 O = SiO 2 + 4H 2

SiH 4 + 2NaOH + H 2 O = 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 monocrystals 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 opal mineral: silica gel is artificially obtained, consisting of colloidal SiO 2 particles and is a very good adsorbent. Glassy SiO 2 is known as quartz glass.

Physical properties

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

Chemical properties

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

SiO 2 + 2NaOH = Na 2 SiO 3 + H 2 O

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

SiO 2 + K 2 O = K 2 SiO 3;

SiO 2 + CaO = CaSiO 3

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

SiO 2 + Na 2 CO 3 = Na 2 SiO 3 + CO 2

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

SiO 2 + 6HF = H 2 SiF 6 + 2H 2 O

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

SiO 2 + 4HF (gas) = ​​SiF 4 + 2H 2 O

SiO 2 + 2F 2 = SiF 4 + O 2

Silicic acid

Known:

Orthosilicic acid H 4 SiO 4;

Metasilicic (silicic) acid H 2 SiO 3;

Di- and polysilicic acids.

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

Methods of obtaining

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

Na 2 SiO 3 + 2HCl = H 2 SiO 3 ↓ + 2NaCl

2. Hydrolysis of chlorosilanes: SiCl 4 + 4H 2 O = 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 final product.

H 4 SiO 4 → H 2 SiO 3 → SiO 2

Silicates - silicic acid salts

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

Na 2 SiO 3 + H 2 O = NaHSiO 3 + NaOH

SiO 3 2- + H 2 O = 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 = H 2 SiO 3 ↓ + K 2 CO 3

SiO 3 + CO 2 + H 2 O = H 2 SiO 3 ↓ + CO 3

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

Among 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, that is, it is a mixture of sodium and calcium silicates. It is obtained by fusing soda Na 2 CO 3, limestone CaCO 3 and sand SiO 2;

Na 2 CO 3 + CaCO 3 + 6SiO 2 = Na 2 O CaO 6SiO 2 + 2CO 2

Cement

Powdered binder, which forms a plastic mass when interacting with water, which over time turns into a solid stone-like body; basic building material.

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

Silicon is one of the most demanded elements in technology and industry. It owes this to its unusual properties. Today, there are many different compounds of this element, which play an important role in the synthesis and creation of technical products, dishes, glass, equipment, construction and finishing materials, jewelry and other industries.

General characteristics of silicon

If we consider the position of silicon in the periodic table, then we can say this:

1. It is located in the IV group of the main subgroup.
2. Serial number 14.
3. Atomic mass 28.086.
4. Chemical symbol Si.
5. The name is silicon, or in Latin - silicium.
6. The electronic configuration of the outer layer is 4e: 2e: 8e.

The crystal lattice of silicon is similar to that of diamond. Atoms are located in the nodes, its type is cubic face-centered. However, due to the longer bond length, the physical properties of silicon are very different from the properties of the allotropic modification of carbon.

Physical and chemical properties

A few more variations of silicon dioxide:

• quartz;
• river and;
• flint;
• feldspars.

The use of silicon in these forms is realized in construction, engineering, radio electronics, chemical industry, metallurgy. All the listed oxides together refer to a single substance - silica.

Silicon carbide and its applications

Silicon and its compounds are also present. One of these materials is carborundum or carbide of this element. Chemical formula SiC. It occurs naturally in the form of the mineral moissanite.

In its pure form, a compound of carbon and silicon is beautiful transparent crystals resembling diamond structures. However, for technical purposes, substances colored green and black are used.

The main characteristics of this substance, allowing it to be used in metallurgy, technology, chemical industry, are as follows:

• wide-gap semiconductor;
• very high degree of strength (7 on the Mohs scale);
• resistant to high temperatures;
• excellent electrical resistance and thermal conductivity.

All this makes it possible to use carborundum as an abrasive material in metallurgy and chemical synthesis. And also on its basis to manufacture LEDs of a wide spectrum of action, parts for glass furnaces, nozzles, torches, jewelry (moissanite is valued higher than cubic zirconia).

Silane and its meaning

The hydrogen compound of silicon is called silane and cannot be obtained by direct synthesis from the starting materials. To obtain it, silicides of various metals are used, which are treated with acids. As a result, gaseous silane is released and a metal salt is formed.

Interestingly, the compound in question is never formed alone. Always as a result of the reaction, a mixture of mono-, di- and trisilane is obtained, in which silicon atoms are connected to each other in chains.

By their properties, these compounds are strong reducing agents. At the same time, they themselves are easily oxidized by oxygen, sometimes with an explosion. With halogens, reactions are always violent, with a large release of energy.

The fields of application of silanes are as follows:

1. Reactions of organic synthesis, as a result of which important organosilicon compounds are formed - silicones, rubbers, sealants, lubricants, emulsions and others.
2. Microelectronics (liquid crystal monitors, integrated technical circuits, etc.).
3. Obtaining ultrapure polysilicon.
4. Dentistry with prosthetics.

Thus, the importance of silanes in the modern world is high.

Silicic acid and silicates

The hydroxide of the element in question is different silicic acids. Allocate:

• meta;
• ortho;
• polysilicon and other acids.

All of them are united by common properties - extreme instability in a free state. They decompose easily when exposed to temperature. Under normal conditions, they do not exist for long, turning first into a sol, and then into a gel. After drying, such structures are called silica gels. They are used as adsorbents in filters.

From the point of view of industry, silicic acid salts - silicates are important. They underlie the production of substances such as:

• glass;
• concrete;
• cement;
• zeolite;
• kaolin;
• porcelain;
• faience;
• crystal;
• ceramics.

Alkali metal silicates are soluble, all others are not. Therefore, sodium and potassium silicate is called liquid glass. Ordinary office glue is the sodium salt of silicic acid.

But the most interesting compounds are still glasses. What kind of variants of this substance have not been invented! Today they receive color, optical, matte versions. Glassware is striking in its magnificence and variety. By adding certain metal and non-metal oxides to the mixture, a wide variety of glass types can be produced. Sometimes even the same composition, but a different percentage of the components leads to a difference in the properties of the substance. An example is porcelain and earthenware, the formula of which is SiO 2 * AL 2 O 3 * K 2 O.

It is a form of ultra-pure product, the composition of which is described as silicon dioxide.

Silicon compound discoveries

Over the past few years of research, it has been proven that silicon and its compounds are the most important participants in the normal state of living organisms. A deficiency or excess of this element is associated with diseases such as:

• tuberculosis;
• arthritis;
• cataract;
• leprosy;
• dysentery;
• rheumatism;
• hepatitis and others.

The aging processes themselves are also associated with the quantitative content of silicon. Numerous experiments on mammals have proven that with a lack of an element, heart attacks, strokes, cancer occur, and the hepatitis virus is activated.

Silicon (Si) - stands in the 3rd period, IV group 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, dissolves in metal melts. Crystalline silicon is a dark gray crystals with a steel 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 external energy level, silicon has 4 electrons, which determines its oxidation states: +4, -4, -2. Valence - 2, 4. Amorphous silicon is more reactive than crystalline. 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 interacts only with a mixture of nitric and hydrofluoric acids:

In relation to metals, it behaves differently: in molten Zn, Al, Sn, Pb, it dissolves well, but does not react with them; with other metal melts - with Mg, Cu, Fe, silicon interacts with the formation of silicides: Si + 2Mg = Mg2Si. Silicon burns in oxygen: Si + O2 = SiO2 (sand).

Silicon dioxide or silica- permanent connection Si, widespread in nature. Reacts with its fusion with alkalis, basic oxides, forming silicic acid salts - silicates. Receiving: in industry, pure silicon is obtained by reducing silicon dioxide with coke in electric furnaces: SiO2 + 2C = Si + 2CO ?.

In the laboratory, silicon is obtained by calcining white sand with magnesium or aluminum:

SiO2 + 2Mg = 2MgO + Si.

3SiO2 + 4Al = Al2O3 + 3Si.

Silicon forms acids: H2 SiO3 - meta-silicic acid; H2 Si2O5 - di-metasilicic acid.

Being in nature: quartz mineral - SiO2. Quartz crystals have the shape of a hexagonal prism, colorless and transparent, called rock crystal. Amethyst - lilac colored rock crystal; smoky topaz is brownish; 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 (ciliated 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. Particle sizes are intermediate between true solutions, suspensions and emulsions. Have colloidal particles molecular or ionic composition.

There are three types of internal structure of primary particles.

1. Suspenzoids (or irreversible colloids)- heterogeneous systems, the properties of which can be determined by a developed interface. 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 precipitates after evaporation do not form sols again. Their concentration is low - 0.1%. They differ slightly from the viscosity of the dispersed medium.

Suspenzoids can be obtained:

1) methods of dispersion (crushing of large bodies);

2) by condensation methods (obtaining insoluble compounds by means of exchange reactions, hydrolysis, etc.).

The spontaneous decrease in dispersion in suspensoids depends on the free surface energy. To obtain a long-lasting suspension, conditions are necessary for its stabilization.

Stable dispersed systems:

1) dispersion medium;

2) dispersed phase;

3) a stabilizer of a dispersed system.

The stabilizer can be ionic, molecular, but most often - high molecular weight.

Protective colloids- high molecular weight compounds that are added for stabilization (proteins, peptides, polyvinyl alcohol, etc.).

2. Associative (or micellar colloids) - semi-colloids arising at a sufficient concentration of molecules consisting of hydrocarbon radicals (diphilic molecules) of low-molecular substances when they are associated 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 weight substances with high molecular weight. Their molecules have the size of colloidal particles (macromolecules).

Diluted solutions of colloids of high molecular weight compounds are homogeneous solutions. With strong dilution, 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, again goes into solution.

CPU? Sand? What associations do you have with this word? Maybe Silicon Valley?
Anyway, we come across silicon every day and if you are interested to know what Si is and what it is eaten with, please, under cat.

Introduction

As a student of one of the Moscow universities, specializing in nanomaterials, I would like to acquaint you, dear reader, with the most important chemical elements of our planet. For a long time I was choosing where to start, carbon or silicon, and still decided to stop at Si, because the heart of any modern gadget is based on it, so to speak, of course. I will try to express my thoughts as simply and easily as possible, having written this material I was counting mainly on beginners, but more advanced people will be able to learn something interesting, I would also like to say that the article was written solely to broaden the horizons of those interested. And so let's get started.

Silicium

Silicon (lat. Silicium), Si, a 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: 28Si (92.27%), 29Si (4.68%) and 30Si (3.05%).
Density (at standard) 2.33 g / cm?
Melting point 1688 K


Powdered Si

Historical reference

Silicon 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 silicon compounds associated with their processing - the manufacture of glass - began around 3000 BC. NS. (in Ancient Egypt). The earliest known silicon compound is SiO2 oxide (silica). In the 18th century, silica was considered a simple body and referred to as "lands" (which is 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 silicon from silicon fluoride SiF4, reducing the latter with metallic potassium. The new element was given the name "silicium" (from Latin silex - flint). The Russian name was introduced by G.I.Hess in 1834.

Silicon is very common in nature in the composition of ordinary sand

Distribution of silicon in nature

In terms of abundance in the earth's crust, silicon is the second (after oxygen) element, its average content in the lithosphere is 29.5% (by weight). In the earth's crust, Silicon plays the same primary role as carbon in the animal and plant world. For the geochemistry of silicon, its extremely strong bond with oxygen is important. About 12% of the lithosphere is silica SiO2 in the form of the mineral quartz and its varieties. 75% of the lithosphere is composed of various silicates and aluminosilicates (feldspars, micas, amphiboles, etc.). The total number of minerals containing silica exceeds 400.

Physical properties of Silicon

I think it's not worth dwelling here, all physical properties are freely available, but I will list the most basic ones.
Boiling point 2600 ° С
Silicon is transparent to long-wave infrared rays
Dielectric constant 11.7
Mohs hardness of Silicon 7.0
I would like to say that silicon is a brittle material; noticeable plastic deformation begins at temperatures above 800 ° C.
Silicon is a semiconductor, which is why it is of great use. The electrical properties of silicon are highly dependent on impurities.

Chemical properties of Silicon

Of course, there is a lot to say, but I will focus on the most interesting. In Si compounds (similar to carbon), it is 4-valency.
Due to the formation of a protective oxide film, silicon is stable in air even at elevated temperatures. In oxygen, it is oxidized starting from 400 ° C, forming silicon oxide (IV) SiO2.
Silicon is resistant to acids and dissolves only in a mixture of nitric and hydrofluoric acids, easily dissolves in hot alkali solutions with the evolution of hydrogen.
Silicon forms 2 groups of oxygenated silanes - siloxanes and siloxenes. Silicon reacts with nitrogen at temperatures above 1000 ° С. Of great practical importance is Si3N4 nitride, which does not oxidize in air even at 1200 ° С, is resistant to acids (except nitric) and alkalis, as well as to molten metals and slags, which makes its valuable material for the chemical industry, as well as for the production of refractories. Silicon compounds with carbon (silicon carbide SiC) and boron (SiB3, SiB6, SiB12) are distinguished by their high hardness, as well as thermal and chemical resistance.

Getting Silicon

I think this is the most interesting part, here we will dwell in more detail.
Depending on the purpose, they are distinguished:
1. Electronic grade silicon(so-called "electronic silicon") - the highest quality silicon with a silicon content of more than 99.999% by weight, the electrical resistivity of electronic grade silicon can be in the range from about 0.001 to 150 Ohm cm, but the resistance value must be provided exclusively a given impurity, that is, the ingress of other impurities into the crystal, even if they provide a given specific electrical resistance, is, as a rule, unacceptable.
2. Solar grade silicon(the so-called "solar silicon") - silicon with a silicon content of over 99.99% by weight, used for the production of photovoltaic converters (solar cells).


3. Technical silicon- blocks of silicon of polycrystalline structure, obtained by the method of carbothermal reduction from pure quartz sand; contains 98% silicon, the main impurity is carbon, is distinguished by a high content of alloying elements - boron, phosphorus, aluminum; is mainly used to obtain polycrystalline silicon.

Silicon of technical purity (95-98%) is obtained in an electric arc by reduction of silica SiO2 between graphite electrodes. In connection with the development of semiconductor technology, methods have been developed for obtaining pure and ultrapure silicon. This requires a preliminary synthesis of the purest starting silicon compounds, from which silicon is extracted by reduction or thermal decomposition.
Polycrystalline silicon ("polysilicon") - the purest form of industrially produced silicon - is a semi-finished product obtained by purifying commercial silicon by chloride and fluoride methods and used for the production of mono- and multicrystalline silicon.
Traditionally, polycrystalline silicon is obtained from technical silicon by converting it into volatile silanes (monosilane, chlorosilanes, fluorosilanes), followed by separation of the resulting silanes, rectification purification of the selected silane, and reduction of the silane to metallic silicon.
Pure semiconductor silicon is obtained in two forms: polycrystalline(reduction of SiCl4 or SiHCl3 with zinc or hydrogen, thermal decomposition of SiI4 and SiH4) and monocrystalline(crucible-free zone melting and "pulling" a single crystal from molten silicon - the Czochralski method).

Here you can see the process of growing silicon using the Czochralski method.

Czochralski method- a method of growing crystals by pulling them up from the free surface of a large volume of the melt with the initiation of the onset of crystallization by bringing a seed crystal (or several crystals) of a given structure and crystallographic orientation into contact with the free surface of the melt.

Silicon Application

Specially doped silicon is widely used as a material for the manufacture of semiconductor devices (transistors, thermistors, power rectifiers, thyristors; solar cells used in spacecraft, as well as many other things).
Since silicon is transparent to rays with a wavelength of 1 to 9 microns, it is used in infrared optics.
Silicon has diverse and ever expanding fields of application. In metallurgy Si
It is used to remove oxygen dissolved in molten metals (deoxidation).
Silicon is a constituent part of a large number of iron and non-ferrous metal alloys.
Typically, Silicon gives alloys increased resistance to corrosion, improves their casting properties and increases mechanical strength; however, at higher levels, Silicon can cause brittleness.
The most important are iron, copper and aluminum alloys containing silicon.
Silica is processed by glass, cement, ceramic, electrical and other industries.
Ultrapure silicon is mainly used for the production of single electronic devices (for example, your computer processor) and single-chip microcircuits.
Pure silicon, waste ultrapure silicon, refined metallurgical silicon in the form of crystalline silicon are the main raw materials for solar energy.
Monocrystalline silicon - in addition to electronics and solar energy, is used to make mirrors for gas lasers.

Ultrapure silicon and its product

Silicon in the body

Silicon in the body is 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 a lot of silicon, forming thick deposits of silicon oxide (IV) on the ocean floor when they die off. In cold seas and lakes, biogenic silts enriched with silicon prevail, in tropical seas - lime silts with a low silicon content. Among terrestrial plants, cereals, sedges, palms, and horsetails accumulate a lot of silicon. In vertebrates, the content of silicon oxide (IV) in ash substances is 0.1-0.5%. The largest quantities of silicon are found in dense connective tissue, kidneys, and pancreas. The daily human diet contains up to 1 g of silicon. With a high content of silicon oxide (IV) dust in the air, it enters the lungs of a person and causes a disease - silicosis.

Conclusion

Well that's all, if you have read to the end and delved into a little, then you are one step closer to success. I hope I did not write in vain and at least someone liked the post. Thank you for the attention.

Silicon was discovered and obtained in 1823 by the Swedish chemist Jens Jakob Berzelius.

The second most abundant element in the earth's crust after oxygen (27.6% by mass). Occurs in connections.

Silicon allotropy

Known amorphous and crystalline silicon.

Polycrystalline silicon

Crystal - a dark gray substance with a metallic luster, high hardness, fragile, semiconductor; ρ = 2.33 g / cm 3, t ° pl. = 1415 ° C; bale t ° = 2680 ° C.

It has a diamond-like structure and forms strong covalent bonds. Inert.

Amorphous - brown powder, hygroscopic, diamond-like structure, ρ = 2 g / cm 3, more reactive.

Getting silicon

1) Industry - heating of coal with sand:

2C + SiO 2 t ˚ → Si + 2CO

2) Laboratory - heating sand with magnesium:

2Mg + SiO 2 t ˚ → Si + 2MgO Experience

Chemical properties

Typical non-metal, inert.

As a reducing agent:

1) With oxygen

Si 0 + O 2 t ˚ → Si +4 O 2

2) With fluorine (no heating)

Si 0 + 2F 2 → SiF 4

3) With carbon

Si 0 + C t ˚ → Si +4 C

(SiC - carborundum - hard; used for point and grinding)

4) Does not interact with hydrogen.

Silane (SiH 4) is obtained by the decomposition of metal silicides with acid:

Mg 2 Si + 2H 2 SO 4 → SiH 4 + 2MgSO 4

5) Does not react with acids (Tonly with hydrofluoric acid Si+4 HF= SiF 4 +2 H 2 )

It dissolves only in a mixture of nitric and hydrofluoric acids:

3Si + 4HNO 3 + 18HF → 3H 2 + 4NO + 8H 2 O

6) With alkalis (when heated):

As an oxidizing agent:

7) With metals (silicides are formed):

Si 0 + 2Mg t ˚ → Mg 2 Si -4

Silane - SiH 4

Physical properties: Colorless gas, poisonous, t ° pl. = -185 ° C, temp. = -112 ° C.

Getting silicic acid

The action of strong acids on silicates - Na 2 SiO 3 + 2HCl → 2NaCl + H 2 SiO 3 ↓

Chemical properties:

Decomposes when heated: H 2 SiO 3 t ˚ → H 2 O + SiO 2

Silicic acid salts - silicates.

1) with acids

Na 2 SiO 3 + H 2 O + CO 2 = Na 2 CO 3 + H 2 SiO 3

2) with salts

Na 2 SiO 3 + CaCl 2 = 2NaCl + CaSiO 3 ↓

3) Silicates, which are part of the minerals, under natural conditions are destroyed by the action of water and carbon monoxide (IV) - weathering of rocks:

(K 2 O Al 2 O 3 6SiO 2) (feldspar) + CO 2 + 2H 2 O → (Al 2 O 3 2SiO 2 2H 2 O) (kaolinite (clay)) + 4SiO 2 (silica (sand)) + K 2 CO 3

Application of silicon compounds

Natural silicon compounds - sand (SiO 2) and silicates are used for the production of ceramics, glass and cement.