Chemistry preparation for ZNO and DPA
Comprehensive Edition

PART AND

GENERAL CHEMISTRY

CHEMISTRY OF THE ELEMENTS

CARBON. SILICIAN

Applications of carbon and silicon

Application of carbon

Carbon is one of the most sought after minerals on our planet. Carbon is predominantly used as a fuel for the energy industry. The annual production of hard coal in the world is about 550 million tons. In addition to the use of coal as a heat carrier, a considerable amount of it is processed into coke, which is necessary for the extraction of various metals. For each ton of iron produced as a result of the blast-furnace process, 0.9 tons of coke is spent. Activated charcoal is used in medicine for poisoning and in gas masks.

Graphite is used in large quantities to make pencils. The addition of graphite to steel increases its hardness and resistance to abrasion. Such steel is used, for example, for the production of pistons, crankshafts and some other mechanisms. The ability of the graphite structure to exfoliate allows it to be used as a highly effective lubricant at very high temperatures (about +2500 °C).

Graphite has another very important property - it is an effective moderator of thermal neutrons. This property is used in nuclear reactors. Recently, plastics have been used, in which graphite is added as a filler. The properties of such materials make it possible to use them for the production of many important devices and mechanisms.

Diamonds are used as a good hard material for the manufacture of such mechanisms as grinding wheels, glass cutters, drilling rigs and other devices that require high hardness. Beautifully cut diamonds are used as expensive jewelry, which are called diamonds.

Fullerenes were discovered relatively recently (in 1985), therefore they have not yet found applied applications, but scientists are already conducting research on creating information carriers of huge capacity. Nanotubes are already being used in various nanotechnologies, such as the administration of drugs using a nanoknife, the manufacture of nanocomputers, and much more.

Application of silicon

Silicon is a good semiconductor. Various semiconductor devices are made from it, such as diodes, transistors, microcircuits and microprocessors. All modern microcomputers use silicon-based processors. Silicon is used to make solar cells that can convert solar energy into electrical energy. In addition, silicon is used as an alloying component for the production of high-quality alloy steels.

Silicon in free form was isolated in 1811 by J. Gay-Lussac and L. Tenard by passing vapors of silicon fluoride over metallic potassium, but it was not described by them as an element. The Swedish chemist J. Berzelius in 1823 gave a description of the silicon obtained by him by treating the potassium salt K 2 SiF 6 with potassium metal at high temperature. The new element was given the name "silicon" (from the Latin silex - flint). The Russian name "silicon" was introduced in 1834 by the Russian chemist German Ivanovich Hess. Translated from other Greek. krhmnoz- "cliff, mountain".

Being in nature, getting:

In nature, silicon is found in the form of dioxide and silicates of various compositions. Natural silicon dioxide occurs mainly in the form of quartz, although other minerals exist - cristobalite, tridymite, kitite, cousite. Amorphous silica is found in diatom deposits at the bottom of the seas and oceans - these deposits were formed from SiO 2, which was part of diatoms and some ciliates.
Free silicon can be obtained by calcining fine white sand with magnesium, which is almost pure silicon oxide in chemical composition, SiO 2 +2Mg=2MgO+Si. Industrial grade silicon is obtained by reducing the SiO 2 melt with coke at a temperature of about 1800°C in arc furnaces. The purity of silicon obtained in this way can reach 99.9% (the main impurities are carbon, metals).

Physical properties:

Amorphous silicon has the form of a brown powder, the density of which is 2.0 g/cm 3 . Crystalline silicon - a dark gray, shiny crystalline substance, brittle and very hard, crystallizes in the diamond lattice. It is a typical semiconductor (conducts electricity better than a rubber-type insulator, and worse than a conductor - copper). Silicon is brittle, only when heated above 800 °C does it become plastic. Interestingly, silicon is transparent to infrared radiation starting at a wavelength of 1.1 micrometers.

Chemical properties:

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, with chlorine, bromine and iodine - to form the corresponding easily volatile tetrahalides SiHal 4 . At a temperature of about 1000°C, silicon reacts with nitrogen to form nitride Si 3 N 4 , with boron - thermally and chemically stable borides SiB 3 , SiB 6 and SiB 12 . Silicon does not directly react with hydrogen.
For silicon etching, a mixture of hydrofluoric and nitric acids is most widely used.
Attitude towards alkalis ...
Silicon is characterized by compounds with an oxidation state of +4 or -4.

The most important connections:

Silicon dioxide, SiO 2- (silicic anhydride) ...
...
Silicic acids- weak, insoluble, formed by adding acid to a silicate solution in the form of a gel (gelatinous substance). H 4 SiO 4 (orthosilicon) and H 2 SiO 3 (metasilicon, or silicon) exist only in solution and irreversibly turn into SiO 2 when heated and dried. The resulting solid porous product - silica gel, has a developed surface and is used as a gas adsorbent, desiccant, catalyst and catalyst carrier.
silicates- salts of silicic acids for the most part (except for sodium and potassium silicates) are insoluble in water. Properties....
Hydrogen compounds- analogues of hydrocarbons, silanes, compounds in which silicon atoms are connected by a single bond, Silenes if the silicon atoms are double bonded. Like hydrocarbons, these compounds form chains and rings. All silanes are self-igniting, form explosive mixtures with air, and readily react with water.

Application:

Silicon finds the greatest use in the production of alloys for giving 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.

For some organisms, silicon is an important biogenic element. It is part of the supporting structures in plants and skeletal structures in animals. In large quantities, silicon is concentrated by marine organisms - diatoms, radiolarians, sponges. Large amounts of silicon are concentrated in horsetails and cereals, primarily in the Bamboo and Rice subfamilies, including common rice. 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.

Antonov S.M., Tomilin K.G.
KhF Tyumen State University, 571 groups.

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.

Carbon and silicon are chemical elements of the IVA group of the periodic system. They are in periods 2 and 3, respectively. Carbon and silicon carbon and silicon are chemical elements of the IVA group
periodic system. They are in periods 2 and 3, respectively.
Carbon and silicon are nonmetal elements.

Carbon has 4 electrons in its outer energy level - 2s22p2, like silicon - 3s23p2.

As a result, in compounds with other elements
carbon and silicon atoms most often exhibit degrees
oxidation -4, +2, +4. In a simple substance, the oxidation state
elements is 0.

Discovery history

C
In 1791, the English chemist Tennant
first received free carbon; he
passed phosphorus vapor over calcined
chalk, resulting in the formation
calcium phosphate and carbon. That diamond
burns out when heated
the remainder has been known for a long time. Back in 1751
German emperor Franz I agreed
give a diamond and a ruby ​​for experiments on
burning, after which these experiments even
came into vogue. It turned out that it burns only
diamond, and ruby ​​(alumina with
chromium impurity) withstands without
damage prolonged heating in
focus of the incendiary lens. Lavoisier
set a new diamond burning experience with
using a large incendiary machine
and came to the conclusion that the diamond represents
is crystalline carbon. Second
allotrope of carbon - graphite - in
alchemical period was considered
modified lead luster and
was called plumbago; only in 1740 Pott
discovered the absence of any lead impurity in graphite.
Si
It was the first time in its pure form
separated in 1811
French scientists
Joseph Louis Gay-Lussac and
Louis Jacques Tenard.

origin of name

C
At the beginning of the 19th century in Russian
chemical literature sometimes
used the term "carbohydrate"
(Sherer, 1807; Severgin, 1815); With
1824 Solovyov introduced the name
"carbon". Carbon compounds
have a part of carb (he) in the name
- from lat. carbō (gen. n. carbōnis)
"coal".
Si
In 1825, the Swedish chemist Jöns
Jakob Berzelius in action
metal potassium
silicon fluoride SiF4 received
pure elemental silicon.
The new element was given
the name "silicon" (from lat. silex
- flint). Russian name
"silicon" introduced in 1834
Russian chemist German
Ivanovich Hess. Translated c
other Greek κρημνός - "cliff, mountain".

Physical properties of simple substances carbon and silicon.

Carbon
exists in many allotropic modifications with very
various physical properties. Variety of modifications
due to the ability of carbon to form chemical bonds of different
type.
The following allotropic modifications of carbon are known: graphite, diamond, carbine
and fullerenes.
a) diamond
b) graphite
c) lonsdaleite
d) fullerene - buckyball C60
e) fullerene C540
f) fullerene C70
g) amorphous carbon
h) carbon nanotube

Diamond is a colorless (sometimes yellowish, brownish, green, black, blue, reddish) transparent substance, very strongly refractive

Diamond - colorless (sometimes yellowish, brownish, green, black, blue, reddish)
a transparent substance that refracts light rays very strongly.
It surpasses all known natural substances in hardness. But it is fragile.
Chemically inert, poor conductor of heat and electricity.
Density 3.5 g/cm3.
Each carbon atom in the diamond structure is located in the center of the tetrahedron, with vertices
served by the four nearest atoms. It is the strong bond of carbon atoms that explains
high hardness of diamond.
Graphite is the most common form.
It is a very soft black substance with a metallic luster and conducts well.
electric current and heat. Greasy to the touch, when rubbed, it exfoliates into separate
scales.
tmelt = 3750 °C (melts at a pressure of 10 MPa, sublimates at normal pressure).
Density 2.22 g/cm3.
The structure of graphite is formed by parallel layers of grids consisting of
hexagons with carbon atoms at the vertices. Atoms in each individual layer
are strongly bonded, and the bond between the layers is weak.

Carbin is a synthetic modification of carbon. Black fine crystalline powder. Density 1.9–2 g/cm3. Semiconductor.

Fullerenes are spherical molecules formed by pentagons and hexagons of carbon atoms connected to each other. Vn

Fullerenes are spherical molecules
formed by pentagons and hexagons of carbon atoms,
interconnected. The molecules are hollow inside. AT
To date, fullerenes of the composition C60, C70, etc. have been obtained.

10. Silicon. Crystalline silicon is a dark gray substance with a metallic luster, has a cubic diamond structure, but is significantly

Silicon.
Crystalline silicon is a dark gray substance with a metallic
brilliance, has a cubic structure of diamond, but is significantly inferior to it in terms of
hardness, rather brittle. Melting point 1415 °C, temperature
boiling point 2680 °C, density 2.33 g/cm3. Has semiconductor
properties, its resistance decreases with increasing temperature.
Amorphous silicon is a brown powder based on highly disordered
diamond-like structure. More reactive than
crystalline silicon.

11. Chemical properties

FROM
Interaction with non-metals
C + 2S = CS2. C + O2 = CO2, C + 2F2 = CF4. C + 2H2 = CH4.
does not interact with nitrogen and phosphorus.
Interaction with metals
Able to interact with metals, forming carbides:
Ca + 2C = CaC2.
Interaction with water
C + H2O = CO + H2.
Carbon is capable of reducing many metals from their
oxides:
2ZnO + C = 2Zn + CO2.
Concentrated sulfuric and nitric acids when heated
oxidize carbon to carbon monoxide (IV):
C + 2H2SO4 = CO2 + 2SO2 + 2H2O;

12.

Si
Interaction with non-metals
Si + 2F2 = SiF4. Si + 2Cl2 = SiCl4. Si + O2 = SiO2.
Si + C = SiC Si + 3B = B3Si. 3Si + 2N2 = Si3N4.
Does not interact with hydrogen.
Interaction with hydrogen halides
Si + 4HF = SiF4 + 2H2,
Interaction with metals
2Ca + Si = Ca2Si.
Interaction with acids
3Si + 4HNO3 + 18HF = 3H2 + 4NO + 8H2O.
Interaction with alkalis
Si + 2NaOH + H2O = Na2SiO3 + H2.

13. Found in nature In the form of carbon dioxide, carbon enters the atmosphere (0.03% by volume). Coal, peat, oil and natural gas - products

Being in nature
In the form of carbon dioxide, carbon enters the atmosphere (0.03% by
volume).
Coal, peat, oil and natural gas are decomposition products
flora of the Earth of ancient times.

14.

Natural inorganic compounds
carbon - carbonates. mineral calcite
CaCO3 is the basis of sedimentary
rocks - limestones. Other
calcium carbonate modifications
known as marble and chalk

15. Silicon in nature

It is widely distributed as silica SiO2 and various
silicates.
For example, granite contains more than 60% silica, while crystalline
quartz is the purest of the natural silicon compounds with
oxygen.
{
Nettle leaves are covered with spiny hairs made of pure oxide.
silicon (IV), which are hollow tubes 1-2 mm long.
The tubules are filled with a liquid containing formic acid.

16. Application of carbon

Graphite is used in the pencil industry. It is also used in
as a lubricant at particularly high or low temperatures.
Diamond, due to its exceptional hardness, is an indispensable abrasive material.
Grinding nozzles of drills have a diamond coating. Besides,
cut diamonds - diamonds are used as gemstones in
jewelry. Due to their rarity, high decorative qualities and
coincidence of historical circumstances, the diamond is invariably the most
an expensive gem.
{
Various compounds are widely used in pharmacology and medicine.
carbon - derivatives of carbonic acid and carboxylic acids.
Carbolene (activated charcoal), used for absorption and elimination from
body of various toxins.

17. Application of silicon

Silicon finds application in semiconductor
technology and microelectronics, in metallurgy as
additives to steels and in the production of alloys.
Silicon compounds serve as the basis for the production
glass and cement. Glass and cement production
engaged in the silicate industry. She 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 bonding paper.

As an independent chemical element, silicon became known to mankind only in 1825. Which, of course, did not prevent the use of silicon compounds in such a number of spheres that it is easier to list those where the element is not used. This article will shed light on the physical, mechanical and useful chemical properties of silicon and its compounds, applications, and we will also talk about how silicon affects the properties of steel and other metals.

To begin with, let's dwell on the general characteristics of silicon. From 27.6 to 29.5% of the mass of the earth's crust is silicon. In sea water, the concentration of the element is also fair - up to 3 mg / l.

In terms of prevalence in the lithosphere, silicon occupies the second place of honor after oxygen. However, its most well-known form, silica, is an oxide, and it is precisely its properties that have become the basis for such a wide application.

This video will tell you what silicon is:

Concept and features

Silicon is a non-metal, but under different conditions it can exhibit both acidic and basic properties. It is a typical semiconductor and is extremely widely used in electrical engineering. Its physical and chemical properties are largely determined by the allotropic state. Most often, they deal with the crystalline form, since its qualities are more in demand in the national economy.

• Silicon is one of the basic macronutrients in the human body. Its lack has a detrimental effect on the condition of bone tissue, hair, skin, nails. In addition, silicon affects the performance of the immune system.
• In medicine, the element, or rather, its compounds, found their first use in this capacity. Water from wells lined with flint was not only clean, but also had a positive effect on resistance to infectious diseases. Today, compounds with silicon serve as the basis for drugs against tuberculosis, atherosclerosis, and arthritis.
• In general, a non-metal is inactive, however, it is difficult to find it in its pure form. This is due to the fact that in air it is quickly passivated by a layer of dioxide and ceases to react. When heated, the chemical activity increases. As a result, humanity is much more familiar with the compounds of matter, and not with itself.

So, silicon forms alloys with almost all metals - silicides. All of them are distinguished by their refractoriness and hardness and are used in their respective areas: gas turbines, furnace heaters.

A non-metal is placed in the table of D. I. Mendeleev in group 6 along with carbon, germanium, which indicates a certain commonality with these substances. So, with carbon, it is “in common” with the ability to form compounds of the organic type. At the same time, silicon, like germanium, can exhibit the properties of a metal in some chemical reactions, which is used in synthesis.

Pros and cons

Like any other substance in terms of application in the national economy, silicon has certain useful or not very qualities. They are important for determining the area of ​​\u200b\u200buse.

• A significant advantage of the substance is its availability. In nature, however, it is not in a free form, but still, the technology for obtaining silicon is not so complicated, although it is energy-consuming.
• The second most important advantage is multiple compound formation with extraordinary benefits. These are silanes, and silicides, and dioxide, and, of course, various silicates. The ability of silicon and its compounds to form complex solid solutions is practically infinite, which makes it possible to endlessly obtain a variety of variations of glass, stone and ceramics.
• Semiconductor properties non-metal provides him with a place as a base material in electrical and radio engineering.
• Nonmetal is non-toxic, which allows application in any industry, and at the same time does not turn the technological process into a potentially dangerous one.

The disadvantages of the material include only relative brittleness with good hardness. Silicon is not used for load-bearing structures, but this combination makes it possible to properly process the surface of crystals, which is important for instrumentation.

Let's now talk about the main properties of silicon.

Properties and characteristics

Since crystalline silicon is most often used in industry, it is precisely its properties that are more important, and it is they that are given in the technical specifications. The physical properties of a substance are:

• melting point - 1417 C;
• boiling point - 2600 C;
• density is 2.33 g/cu. see, which indicates fragility;
• heat capacity, as well as thermal conductivity, are not constant even on the purest samples: 800 J / (kg K), or 0.191 cal / (g deg) and 84-126 W / (m K), or 0.20-0, 30 cal/(cm sec deg), respectively;
• transparent to long-wave infrared radiation, which is used in infrared optics;
• dielectric constant - 1.17;
• hardness on the Mohs scale - 7.

The electrical properties of a non-metal are highly dependent on impurities. In industry, this feature is used by modulating the desired type of semiconductor. At normal temperatures, silicon is brittle, but when heated above 800 C, plastic deformation is possible.

The properties of amorphous silicon are strikingly different: it is highly hygroscopic and reacts much more actively even at normal temperatures.

The structure and chemical composition, as well as the properties of silicon, are discussed in the video below:

Composition and structure

Silicon exists in two allotropic forms, equally stable at normal temperature.

• Crystal It has the appearance of a dark gray powder. The substance, although it has a diamond-like crystal lattice, is fragile - due to the too long bond between the atoms. Of interest are its semiconductor properties.
• At very high pressures, you can get hexagonal modification with a density of 2.55 g / cu. see However, this phase has not yet found practical significance.
• Amorphous- Brown powder. Unlike the crystalline form, it reacts much more actively. This is due not so much to the inertness of the first form, but to the fact that in air the substance is covered with a layer of dioxide.

In addition, it is necessary to take into account another type of classification associated with the size of the silicon crystal, which together form a substance. The crystal lattice, as is known, implies the ordering not only of atoms, but also of the structures that these atoms form - the so-called long-range order. The larger it is, the more homogeneous the substance will be in properties.

• monocrystalline– the sample is a single crystal. Its structure is as ordered as possible, the properties are homogeneous and well predictable. It is this material that is most in demand in electrical engineering. However, it also belongs to the most expensive type, since the process of obtaining it is complicated, and the growth rate is low.
• Multicrystalline– the sample consists of a number of large crystalline grains. The boundaries between them form additional defective levels, which reduces the performance of the sample as a semiconductor and leads to faster wear. The technology for growing a multicrystal is simpler, and therefore the material is cheaper.
• Polycrystalline- consists of a large number of grains arranged randomly relative to each other. This is the purest variety of industrial silicon, used in microelectronics and solar energy. Quite often it is used as a raw material for growing multi- and single crystals.
• Amorphous silicon also occupies a separate position in this classification. Here the order of the atoms is maintained only at the shortest distances. However, in electrical engineering, it is still used in the form of thin films.

Non-metal production

It is not so easy to obtain pure silicon, given the inertness of its compounds and the high melting point of most of them. In industry, carbon dioxide reduction is most often used. The reaction is carried out in arc furnaces at a temperature of 1800 C. Thus, a non-metal with a purity of 99.9% is obtained, which is not enough for its use.

The resulting material is chlorinated in order to obtain chlorides and hydrochlorides. Then the compounds are purified by all possible methods from impurities and reduced with hydrogen.

It is also possible to purify the substance by obtaining magnesium silicide. The silicide is subjected to the action of hydrochloric or acetic acid. Silane is obtained, and the latter is purified by various methods - sorption, rectification, and so on. Then the silane is decomposed into hydrogen and silicon at a temperature of 1000 C. In this case, a substance with an impurity fraction of 10 -8 -10 -6% is obtained.

Substance use

For industry, the electrophysical characteristics of non-metal are of the greatest interest. Its single-crystal form is an indirect-gap semiconductor. Its properties are determined by impurities, which makes it possible to obtain silicon crystals with desired properties. So, the addition of boron, indium makes it possible to grow a crystal with hole conductivity, and the introduction of phosphorus or arsenic - a crystal with electronic conductivity.

• Silicon literally serves as the basis of modern electrical engineering. Transistors, photocells, integrated circuits, diodes and so on are made from it. Moreover, the functionality of the device is almost always determined only by the near-surface layer of the crystal, which leads to very specific requirements for surface treatment.
• In metallurgy, technical silicon is used both as an alloy modifier - it gives greater strength, and as a component - in, for example, and as a deoxidizer - in the production of cast iron.
• Ultra-pure and refined metallurgical form the basis of solar energy.
• Non-metal dioxide occurs in nature in very different forms. Its crystalline varieties - opal, agate, carnelian, amethyst, rock crystal, have found their place in jewelry. Modifications that are not so attractive in appearance - flint, quartz, are used in metallurgy, and in construction, and in radio electrical engineering.
• The compound of a non-metal with carbon - carbide, is used in metallurgy, in instrument making, and in the chemical industry. It is a wide-gap semiconductor, characterized by high hardness - 7 on the Mohs scale, and strength, which allows it to be used as an abrasive material.
• Silicates - that is, salts of silicic acid. Unstable, easily decomposed under the influence of temperature. They are remarkable in that they form numerous and varied salts. But the latter are the basis for the production of glass, ceramics, faience, crystal, and. We can safely say that modern construction is based on a variety of silicates.
• Glass represents the most interesting case here. It is based on aluminosilicates, but insignificant impurities of other substances - usually oxides - give the material a lot of different properties, including color. -, earthenware, porcelain, in fact, has the same formula, although with a different ratio of components, and its diversity is also amazing.
• A non-metal has another ability: it forms carbon-type compounds, in the form of a long chain of silicon atoms. Such compounds are called organosilicon compounds. The scope of their application is no less known - these are silicones, sealants, lubricants, and so on.

Silicon is a very common element and is extremely important in many areas of the national economy. Moreover, not only the substance itself is actively used, but all its various and numerous compounds.

This video will talk about the properties and applications of silicon: