One of the most sought-after elements in technology and industry is silicon. To this he owes his unusual properties. Today there are a lot of various compounds of this element, which play an important role in the synthesis and creation of technical products, dishes, glass, equipment, building and finishing materials, jewelry and other industries.
General characteristics of silicon
If we consider the position of silicon in the periodic system, we can say this:
- Located in the IV group of the main subgroup.
- Sequence number 14.
- The atomic mass is 28.086.
- Chemical symbol Si.
- The name – silicon, or in Latin – silicium.
- Electronic configuration of the outer layer 4e: 2e: 8e.
The crystal lattice of silicon is similar to a diamond lattice. The atoms are located in the nodes, its type is cubic face-centered. However, due to the greater bond length, the physical properties of silicon are very different from the properties of the allotropic modification of carbon.
Physical and chemical properties
There are two allotropic modifications of this element: amorphous and crystalline. They are very similar. However, as in the case of other substances, the main difference between them is the crystal lattice of silicon.
In addition, both modifications are powders of different colors.
1. Crystalline silicon is a dark gray, shiny metal-like powder. Its structure corresponds to diamond, but its properties are excellent. He has:
- low hardness;
- semiconductor properties;
- melting point 1415 0 С;
- density of 2.33 g / cm 3;
- boiling point 2700 0 C.
Its chemical activity is low compared with the other allotropic form.
2. Amorphous silicon – brown-brown powder, has the structure of a highly disordered diamond. Chemical activity is quite high.
In general, it should be noted that silicon does not like to react. To make it react, a temperature of at least 400-500 ° C is needed. Under these conditions, various chemical compounds of silicon are formed. Such as:
Silicon can interact with nitric acid or alkali, which is called the etching process. Silicone compounds that are becoming more common today are widespread.
Being in nature
Silicon in nature is contained in a fairly significant amount. It is in second place after the oxygen prevalence. Its mass fraction is about 30%. Sea water also contains this element at an approximate concentration of 3 mg / l. Therefore, it cannot be said that silicon in nature is a rare element.
On the contrary, there is a mass of various rocks and minerals, in which it is found and from which it can be mined. The most common natural silicon compounds are as follows:
- Silica. Chemical formula SiO2. There is a fairly large variety of forms of minerals and rocks based on it: sand, flint, feldspar, quartz, rock crystal, amethyst, chalcedony, carnelian, opal, jasper, and others.
- Silicates and aluminosilicates. Kaolin, spars, mica, salts of silicic acid, asbestos, talc.
Thus, the distribution of silicon in nature is wide, and its compounds are popular and in demand among people for technical applications.
Silicon and its compounds
Since the considered element cannot exist in its pure form, its various connections are important. From a chemical point of view, it can exhibit three oxidation states: +2, +4, -4. On the basis of this, as well as from its inertness, but special in the structure of the crystal lattice, it forms the following main types of substances:
- binary compounds with non-metals (silane, carbide, nitride, phosphide, etc.);
- silicic acid;
- metal silicates.
Let’s take a closer look at the significance of silicon and its compounds, which are the most common and popular for people.
There are two types of this substance, expressed by the formulas:
However, the most common is dioxide. It exists in nature as very beautiful semi-precious stones:
The use of silicon in this form has found its use in the manufacture of jewelry. Incredibly beautiful gold and silver jewelry are made with these semi-precious and semi-precious stones.
A few more variations of silicon dioxide:
The use of silicon in these types is implemented in construction, engineering, electronics, chemical industry, metallurgy. Together, these oxides are a single substance – silica.
Silicon carbide and its application
Silicon and its compounds are materials of the future and the present. One of such materials is carborundum or carbide of this element. The chemical formula of SiC. It occurs in nature in the form of the mineral moissanite.
In its pure form, the compound of carbon and silicon are beautiful transparent crystals that resemble diamond structures. However, for technical purposes, substances painted in green and black are used.
The main characteristics of this substance, allowing its use in metallurgy, engineering, 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 allows the use of carborundum as an abrasive material in metallurgy and chemical syntheses. And also on its basis to produce a broad-spectrum LEDs, parts for glass melting furnaces, nozzles, torches, jewelry (moissanite is valued above cubic zirconia).
Silane and its value
The hydrogen compound 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. The reaction always produces a mixture of mono-, di-, and trisilane, in which the silicon atoms are interconnected in chains.
According to 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 violent always, with a large release of energy.
The silane application fields are as follows:
- Reactions of organic syntheses, as a result of which important organosilicon compounds are formed – silicones, rubbers, sealants, lubricants, emulsions and others.
- Microelectronics (liquid crystal monitors, integrated technical circuits, etc.).
- Getting ultrapure polysilicon.
- Dentistry during prosthetics.
Thus, the value of silanes in the modern world is high.
Silicic acid and silicates
The hydroxide of the considered element is different silicic acids. Allocate:
- polysilicon and other acids.
All of them share common properties – extreme instability in a free state. They easily decompose under the action of temperature. Under normal conditions, there are not 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.
Important from the point of view of industry are silicic acid salts of silicates. They are the basis for the production of substances such as:
Alkali metal silicates are soluble, all others are not. Therefore, sodium and potassium silicate is called liquid glass. Regular office glue – this is the sodium salt of silicic acid.
But the most interesting compounds are still glass. What only options for this substance come up with! Today receive color, optical, matte options. Glassware amazes with its magnificence and diversity. By adding certain metal oxides and non-metals to the mixture, you can get a variety of glass types. Sometimes even the same composition, but a different percentage of components leads to a difference in the properties of the substance. An example would be porcelain and earthenware, whose formula is SiO2 * AL2O3 * K2O.
Quartz glass is a form of high purity product, whose composition is described as silicon dioxide.
Discoveries in the field of silicon compounds
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. With the lack or excess of this element associated diseases such as:
- hepatitis and others.
The aging process of the body itself is also associated with the quantitative content of silicon. Numerous experiments on mammals have shown that with a deficiency of an element, heart attacks, strokes, cancer occur and the hepatitis virus is activated.