Silicon and its compounds. Silicon in nature. Application of silicon

One of the most demanded in the technology and industry elements is silicon. This he owes his unusual properties. Today, there are many different compounds of this element that play an important role in the synthesis and creation of technical products, glassware, equipment, building and finishing materials, jewelry and other industries.

General characteristics of silicon

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

1. It is located in the IV group of the main subgroup.
2. The serial number is 14.
3. The atomic mass is 28,086.
4. Chemical symbol Si.
5. The name is silicon, or in Latin - silicium.
6. Electronic configuration of the outer layer 4e: 2e: 8e.

The crystal lattice of silicon is similar to the lattice of a diamond. At the nodes are atoms, whose type is cubic face-centered. However, due to the longer bond length, the physical properties of silicon are very different from the properties of 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 this case, both modifications are powders of different colors.

1. Crystalline silicon is a dark gray shiny powder, similar to metal. Its structure corresponds to a diamond, but the properties are different. He has:

• Fragility;
• Low hardness;
• Semiconductor properties;
• Melting point 1415 ⁰ С;
• Density of 2.33 g / cm ³ ;
• The boiling point is 2700 ^° C.

Its chemical activity is low in comparison with other allotropic form.

2. Amorphous silicon is a brown-brown powder with a structure of strongly disordered diamond. The chemical activity is quite high.

In general, it should be noted that silicon does not like to join the reaction. 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:

• Oxides;
• Halides;
• Silicides;
• Nitrides;
• Borides;
• Carbides.

Perhaps the interaction of silicon with nitric acid or alkali, which is called the etching process. Silicone compounds are widely spread, which are becoming more widespread today.

Being in nature

Silicon in nature is contained in a fairly large amount. It is in second place after oxygen in prevalence. Its mass fraction is about 30%. Sea water also contains this element in an approximate concentration of 3 mg / l. Therefore, it can not be said that silicon in nature is a rare element.

On the contrary, there are a lot of different rocks and minerals in the composition of which it is found and from which it can be extracted. The most common natural silicon compounds are as follows:

1. Silica. Chemical formula of SiO ₂ . There is a rather wide variety of forms of minerals and rocks based on it: sand, flint, feldspar, quartz, rock crystal, amethyst, chalcedony, carnelian, opal, jasper and others.
2. Silicates and aluminosilicates. Kaolin, spar, mica, salts of silicic acid, asbestos, talc.

Thus, the spread in nature of silicon is widespread, and its compounds are popular and popular with people for use in technical purposes.

Silicon and its compounds

Since in its pure form the element under consideration can not exist, therefore, its different connections are of great importance. From the chemical point of view, it can exhibit three oxidation states: +2, +4, -4. Proceeding from this, and also from its inertness, but peculiar in the structure of the crystal lattice, it forms the following main types of substances:

• Binary compounds with non-metals (silane, carbide, nitride, phosphide and so on;
• Oxides;
• Silicic acid;
• Silicates of metals.

Let us examine in more detail the importance of silicon and its compounds, which are the most common and claimed for people.

Silicon Oxides

There are two varieties of this substance, expressed by the formulas:

• SiO;
• SiO2.

However, the most common is dioxide. It exists in nature in the form of very beautiful semiprecious stones:

• agate;
• chalcedony;
• opal;
• cornelian;
• jasper;
• amethyst;
• rhinestone.

The use of silicon in this form has found its application in the production of jewelry. Incredibly beautiful gold and silver jewelry are made with these semiprecious and ornamental stones.

A few more variations of silicon dioxide:

• quartz;
• River and quartz sand ;
• flint;
• Feldspars.

The use of silicon in such types is realized in construction, engineering, radio electronics, chemical industry, and metallurgy. All these oxides are referred to a single substance - silica.

Silicon carbide and its application

Silicon and its compounds are materials of the future and the present. One such material is carborundum or carbide of this element. The chemical formula is SiC. Occurs in nature in the form of a moissanite mineral.

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

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

• Wide-band semiconductor;
• Very high degree of strength (7 on the Mohs scale) ;
• Resistant to high temperatures;
• Excellent electrical stability 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 range of action, details for glass melting furnaces, nozzles, torches, jewelry (moissanite is valued above phianite).

Silan and its meaning

The hydrogen compound of silicon is called silane and can not be obtained by direct synthesis from the starting materials. To produce it, silicides of various metals are used, which are treated with acids. As a result, a 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 the silicon atoms are joined together into chains.

In their properties, these compounds are strong reducing agents. They themselves are easily oxidized by oxygen, sometimes with an explosion. With halogens, turbulent reactions are always, with a large release of energy.

The areas of application of silanes are as follows:

1. Reactions of organic syntheses, which result in the formation of important organosilicon compounds - silicones, rubber, sealants, lubricants, emulsions and others.
2. Microelectronics (liquid crystal monitors, integrated technical schemes, etc.).
3. Production of ultra-pure polysilicon.
4. Dentistry in 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 share common properties - extreme instability in the free state. They easily decompose under the influence of temperature. Under normal conditions, there is not much time, turning first into a sol, and then into a gel. After drying, these structures are called silica gels. They are used as adsorbents in filters.

Important in terms of industry are salts of silicic acids - silicates. They are the basis for obtaining such substances as:

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

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

But the most interesting compounds are all the same glass. What are the only variants of this substance they invented! Today they receive colored, optical, matte options. Glassware amazes with its splendor and variety. When certain metal oxides and non-metals are added to the mixture, a variety of types of glass can be obtained. Sometimes even the same composition, but a different percentage of components leads to a difference in the properties of the substance. An example is porcelain and faience, the formula of which is SiO ₂ * AL ₂ O ₃ * K ₂ O.

Quartz glass is a form of a particularly pure product, the composition of which is described as silicon dioxide.

Discoveries in the field of silicon compounds

In the last 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 a deficiency or excess of this element, diseases such as:

• cancer;
• tuberculosis;
• Arthritis;
• cataract;
• leprosy;
• dysentery;
• rheumatism;
• Hepatitis and others.

The aging processes of the organism are also associated with the quantitative content of silicon. Numerous experiments on mammals have shown that if the element lacks, heart attacks, strokes, cancer occur and the hepatitis virus becomes active.