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 that 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 group IV of the main subgroup.
- Ordinal number 14.
- Atomic mass 28, 086.
- Chemical symbol Si.
- Name - silicon, or in Latin - silicium.
- Electronic configuration of outer layer 4e:2e:8e.
The crystal lattice of silicon is similar to that of diamond. Atoms are located at the nodes, its type is face-centered cubic. 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
There are twoallotropic modifications of this element: amorphous and crystalline. They are very similar. However, as with 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 metal-like powder. Its structure corresponds to diamond, but the properties are different. He has:
- fragility;
- low hardness;
- semiconductor properties;
- melting point 14150C;
- 2.33g/cm3;
- boiling point 27000C.
Its chemical activity is low compared to other allotropic form.
2. Amorphous silicon - brown-brown powder, has the structure of highly disordered diamond. The chemical activity is quite high.
In general, it should be noted that silicon does not like to react. To make it react, you need a temperature of at least 400-5000C. Under these conditions, various chemical compounds of silicon are formed. Such as:
- oxides;
- halides;
- silicides;
- nitrides;
- borides;
- carbides.
Possible interaction of silicon with nitric acid or alkali, which is called the etching process. Organosilicon compounds are widespread and are becoming more and more common today.
Being in nature
Silicon is found in nature in a fairly significant amount. It is in second place after oxygen in terms of 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 is a rare element in nature.
On the contrary, there are many different rocks and minerals in which it occurs and from which it can be mined. The most common natural silicon compounds are as follows:
- Silica. The chemical formula is SiO2. There is a fairly large variety of forms of minerals and rocks based on it: sand, flint, feldspars, quartz, rock crystal, amethyst, chalcedony, carnelian, opal, jasper and others.
- Silicates and aluminosilicates. Kaolin, spars, mica, silicic acid s alts, asbestos, talc.
Thus, silicon is widely distributed in nature, and its compounds are popular and in demand among people for technical applications.
Silicon and its compounds
Since the element in question cannot exist in its pure form, therefore its various compounds are important. From a chemical point of view, it can exhibit three oxidation states: +2, +4, -4. Proceeding from 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 and so on;
- oxides;
- siliconacid;
- metal silicates.
Let's take a closer look at the importance of silicon and its compounds, which are the most common and in demand for people.
Silicon oxides
There are two varieties of this substance, expressed by the formulas:
- SiO;
- SiO2.
However, the most widespread is dioxide. It exists in nature in the form of very beautiful semi-precious stones:
- agate;
- chalcedony;
- opal;
- carnelian;
- jasper;
- amethyst;
- rhinestone.
The use of silicon in this form has found its application in the manufacture of jewelry. Incredibly beautiful gold and silver jewelry is made with these semi-precious and semi-precious stones.
A few more variations of silicon dioxide:
- quartz;
- river and quartz sand;
- flint;
- feldspars.
The use of silicon in these types is implemented in construction work, engineering, radio electronics, the chemical industry, and metallurgy. Together, the listed oxides belong to a single substance - silica.
Silicon carbide and its applications
Silicon and its compounds are the materials of the future and the present. One of these materials is carborundum or the carbide of this element. Chemical formula of SiC. Occurs naturally as the mineral moissanite.
In its pure form, the compound of carbon and silicon is beautifultransparent crystals resembling diamond structures. However, green and black colored substances are used for technical purposes.
The main characteristics of this substance, allowing its use in metallurgy, engineering, chemical industry, are as follows:
- wide gap semiconductor;
- very high strength (7 on the Mohs scale);
- high temperature resistant;
- 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 produce broad-spectrum LEDs, parts for glass melting furnaces, nozzles, torches, jewelry (moissanite is valued more than cubic zirconia).
Silan and its meaning
The hydrogen compound of silicon is called silane and cannot be obtained by direct synthesis from 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 s alt is formed.
Interestingly, the connection 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 interconnected 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, the reactions are always violent, with a large emissionenergy.
The applications of silanes are as follows:
- Reactions of organic synthesis, which result in the formation of important organosilicon compounds - silicones, rubbers, sealants, lubricants, emulsions and others.
- Microelectronics (LCD monitors, integrated technical circuits, etc.).
- Obtaining ultrapure polysilicon.
- 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. Highlight:
- meta;
- ortho;
- polysilicic and other acids.
All of them are united by common properties - extreme instability in the free state. They easily decompose under the influence of 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.
Important, from the point of view of industry, are s alts of silicic acids - silicates. 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 clerical glue - this is sodiumsilicic acid s alt.
But the most interesting compounds are still glasses. No matter how many variants of this substance they came up with! Today they get color, optical, matte options. Glassware is striking in its splendor 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 faience, the formula of which is SiO2AL2O3K 2O.
Quartz glass is a form of highly pure product whose composition is described as silicon dioxide.
Discoveries in 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 a lack or excess of this element, diseases such as:
- cancer;
- tuberculosis;
- arthritis;
- cataract;
- leprosy;
- dysentery;
- rheumatism;
- hepatitis and others.
The aging process itself is 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.
