Silicon: application, chemical and physical properties

2024 Author: Angel Austin | [email protected]. Last modified: 2023-12-17 05:14

One of the most common elements in nature is silicium, or silicon. Such a wide distribution speaks of the importance and significance of this substance. This was quickly understood and adopted by people who learned how to properly use silicon for their own purposes. Its application is based on special properties, which we will talk about later.

Silicon is a chemical element

If we characterize a given element by position in the periodic system, we can identify the following important points:

1. Ordinal number - 14.
2. The period is the third small one.
3. Group - IV.
4. Subgroup - main.
5. The structure of the outer electron shell is expressed by the formula 3s²3p².
6. The element silicon is denoted by the chemical symbol Si, which is pronounced "silicium".
7. The oxidation states it exhibits: -4; +2; +4.
8. The valency of an atom is IV.
9. The atomic mass of silicon is 28.086.
10. In nature, there are three stable isotopes of this element with mass numbers 28, 29 and 30.

So the atomFrom a chemical point of view, silicon is a well-studied element, many of its various properties have been described.

Discovery history

Since it is the various compounds of the element under consideration that are very popular and massive in content in nature, from ancient times people used and knew about the properties of just many of them. Pure silicon for a long time remained beyond the knowledge of man in chemistry.

The most popular compounds used in everyday life and industry by the peoples of ancient cultures (Egyptians, Romans, Chinese, Russians, Persians and others) were precious and ornamental stones based on silicon oxide. These include:

• opal;
• rhinestone;
• topaz;
• chrysoprase;
• onyx;
• chalcedony and others.

It has also been customary to use quartz and quartz sand in construction since ancient times. However, elemental silicon itself remained undiscovered until the 19th century, although many scientists tried in vain to isolate it from various compounds, using catalysts, high temperatures, and even electric current. These are bright minds like:

• Karl Scheele;
• Gay-Lussac;
• Tenar;
• Humphry Davy;
• Antoine Lavoisier.

Jens Jacobs Berzelius managed to successfully obtain pure silicon in 1823. To do this, he conducted an experiment on the fusion of vapors of silicon fluoride and metallic potassium. As a result, he received an amorphous modification of the element in question. The same scientist proposed a Latin name for the discovered atom.

A little later, in 1855, another scientist - Saint Clair-Deville - managed to synthesize another allotropic variety - crystalline silicon. Since then, knowledge about this element and its properties began to grow very quickly. People realized that it has unique features that can be very intelligently used to meet their own needs. Therefore, today one of the most demanded elements in electronics and technology is silicon. Its use only expands its boundaries every year.

The Russian name for the atom was given by the scientist Hess in 1831. That is what has stuck to this day.

Contained in nature

Silicon is the second most abundant in nature after oxygen. Its percentage in comparison with other atoms in the composition of the earth's crust is 29.5%. In addition, carbon and silicon are two special elements that can form chains by connecting with each other. That is why more than 400 different natural minerals are known for the latter, in which it is contained in the lithosphere, hydrosphere and biomass.

Where exactly is silicon found?

1. In the deep layers of the soil.
2. In rocks, deposits and massifs.
3. At the bottom of bodies of water, especially seas and oceans.
4. In the plants and marine life of the animal kingdom.
5. In humans and land animals.

It is possible to designate several of the most common minerals and rocks, which contain a large amount ofsilicon. Their chemistry is such that the mass content of a pure element in them reaches 75%. However, the specific figure depends on the type of material. So, rocks and minerals containing silicon:

• feldspars;
• mica;
• amphiboles;
• opals;
• chalcedony;
• silicates;
• sandstones;
• aluminosilicates;
• clays and others.

Accumulating in the shells and outer skeletons of marine animals, silicon eventually forms powerful deposits of silica at the bottom of water bodies. This is one of the natural sources of this element.

In addition, it was found that silicium can exist in its pure native form - in the form of crystals. But such deposits are very rare.

Physical properties of silicon

If you characterize the element under consideration by a set of physical and chemical properties, then first of all, it is the physical parameters that should be indicated. Here are a few key ones:

1. Exists in the form of two allotropic modifications - amorphous and crystalline, which differ in all properties.
2. The crystal lattice is very similar to that of diamond, because carbon and silicon are almost the same in this respect. However, the distance between the atoms is different (silicon has more), so the diamond is much harder and stronger. Lattice type - cubic face-centered.
3. The substance is very brittle, becomes plastic at high temperatures.
4. Melting point is 1415˚C.
5. Temperatureboiling point - 3250˚С.
6. Density of matter - 2.33 g/cm³.
7. The color of the connection is silver-gray, with a characteristic metallic sheen.
8. Possesses good semiconductor properties, which can vary with the addition of certain agents.
9. Insoluble in water, organic solvents and acids.
10. Specifically soluble in alkalis.

Designated physical properties of silicon allow people to control it and use it to create various products. For example, the use of pure silicon in electronics is based on the properties of semiconductivity.

Chemical properties

The chemical properties of silicon are very dependent on the reaction conditions. If we talk about a pure substance at standard parameters, then we need to designate a very low activity. Both crystalline and amorphous silicon are very inert. Do not interact with strong oxidizing agents (except fluorine), nor with strong reducing agents.

This is due to the fact that an oxide film SiO₂ is instantly formed on the surface of the substance, which prevents further interactions. It can be formed under the influence of water, air, vapors.

If you change the standard conditions and heat silicon to a temperature above 400˚С, then its chemical activity will greatly increase. In this case, it will react with:

• oxygen;
• all kinds of halogens;
• hydrogen.

With a further increase in temperature, the formation of products atinteraction with boron, nitrogen and carbon. Of particular importance is carborundum - SiC, as it is a good abrasive material.

Also, the chemical properties of silicon are clearly seen in reactions with metals. In relation to them, it is an oxidizing agent, therefore the products are called silicides. Similar compounds are known for:

• alkaline;
• alkaline earth;
• transition metals.

Unusual properties have a compound obtained by fusing iron and silicon. It is called ferrosilicon ceramic and has been successfully used in industry.

Silicon does not interact with complex substances, therefore, of all their varieties, it can only dissolve in:

• royal vodka (a mixture of nitric and hydrochloric acids);
• caustic alkalis.

In this case, the temperature of the solution should be at least 60˚С. All this once again confirms the physical basis of the substance - a diamond-like stable crystal lattice, which gives it strength and inertness.

Methods of obtaining

Obtaining pure silicon is a rather costly process economically. In addition, due to its properties, any method gives only 90-99% pure product, while impurities in the form of metals and carbon remain the same. So just getting the substance is not enough. It should also be qualitatively cleaned of foreign elements.

In general, the production of silicon is carried out in two main ways:

1. From the white sandwhich is pure silicon oxide SiO₂. When it is calcined with active metals (most often with magnesium), a free element is formed in the form of an amorphous modification. The purity of this method is high, the product is obtained with a 99.9 percent yield.
2. A more widespread method on an industrial scale is the sintering of molten sand with coke in specialized thermal kilns. This method was developed by the Russian scientist Beketov N. N.

Further processing consists in subjecting the products to cleaning methods. For this, acids or halogens (chlorine, fluorine) are used.

Amorphous silicon

Characterization of silicon will be incomplete if we do not consider separately each of its allotropic modifications. The first one is amorphous. In this state, the substance we are considering is a brown-brown powder, finely dispersed. It has a high degree of hygroscopicity, exhibits a sufficiently high chemical activity when heated. Under standard conditions, it can only interact with the strongest oxidizing agent - fluorine.

It is not entirely correct to call amorphous silicon a variety of crystalline silicon. Its lattice shows that this substance is only a form of finely dispersed silicon that exists in the form of crystals. Therefore, as such, these modifications are the same compound.

However, their properties differ, therefore it is customary to speak of allotropy. By itself, amorphous silicon hashigh light absorption capacity. In addition, under certain conditions, this indicator is several times higher than that of the crystalline form. Therefore, it is used for technical purposes. In the considered form (powder), the compound is easily applied to any surface, be it plastic or glass. Therefore, it is amorphous silicon that is so convenient for use. The application is based on the manufacture of solar panels of various sizes.

Although the wear of this type of batteries is quite fast, which is associated with abrasion of a thin film of the substance, however, the use and demand is only growing. Indeed, even in a short service life, solar cells based on amorphous silicon are able to provide energy to entire enterprises. In addition, the production of such a substance is waste-free, which makes it very economical.

Get this modification by reducing compounds with active metals, such as sodium or magnesium.

Crystal silicon

Silver gray shiny modification of the element in question. It is this form that is the most common and most in demand. This is due to the set of qualitative properties that this substance possesses.

The characteristic of silicon with a crystal lattice includes a classification of its types, since there are several of them:

1. Electronic quality - the purest and highest quality. It is this type that is used in electronics to create especially sensitive devices.
2. Sunny quality. The name itselfdefines the area of use. It is also a fairly high purity silicon, the use of which is necessary to create high-quality and long-lasting solar cells. Photovoltaic converters created on the basis of a crystalline structure are of higher quality and more durable than those created using an amorphous modification by deposition on various types of substrates.
3. Technical silicon. This variety includes those samples of a substance that contain about 98% of the pure element. Everything else goes to various kinds of impurities:

• boron;
• aluminum;
• chlorine;
• carbon;
• phosphorus and others.

The last variety of the substance in question is used to obtain silicon polycrystals. For this, recrystallization processes are carried out. As a result, in terms of purity, products are obtained that can be attributed to the groups of solar and electronic quality.

By nature, polysilicon is an intermediate product between amorphous and crystalline modification. This option is easier to work with, it is better recycled and cleaned with fluorine and chlorine.

The resulting products can be classified as follows:

• multicilicon;
• monocrystalline;
• profiled crystals;
• silicon scrap;
• technical silicon;
• production waste in the form of fragments and scraps of matter.

Each of them finds application in industry and is useda person completely. Therefore, production processes involving silicon are considered waste-free. This greatly reduces its economic cost without affecting the quality.

Using pure silicon

Silicon production in the industry is established quite well, and its scale is quite voluminous. This is due to the fact that this element, both pure and in the form of various compounds, is widespread and in demand in various branches of science and technology.

Where is pure crystalline and amorphous silicon used?

1. In metallurgy as an alloying additive capable of changing the properties of metals and their alloys. So, it is used in the smelting of steel and iron.
2. Different types of substance are used to make a cleaner version - polysilicon.
3. Compounds of silicon with organic substances - this is a whole chemical industry that has gained particular popularity today. Silicone materials are used in medicine, in the manufacture of dishes, tools and much more.
4. Production of various solar panels. This method of obtaining energy is one of the most promising in the future. Environmentally friendly, cost-effective and durable - the main advantages of such electricity production.
5. Silicon has been used in lighters for a very long time. Even in ancient times, people used flint to create a spark when lighting a fire. This principle is the basis for the production of lighters of various kinds. Today there are species in whichthe flint is replaced with an alloy of a certain composition, which gives an even faster result (sparking).
6. Electronics and solar energy.
7. Production of mirrors in gas laser devices.

Thus, pure silicon has a lot of advantageous and special properties that allow it to be used to create important and necessary products.

Application of silicon compounds

In addition to a simple substance, various silicon compounds are also used, and very widely. There is a whole branch of industry called silicate. It is she who is based on the use of various substances, which include this amazing element. What are these compounds and what do they produce?

1. Quartz, or river sand - SiO₂. It is used for the manufacture of building and decorative materials such as cement and glass. Where these materials are used, everyone knows. No construction is complete without these components, which confirms the importance of silicon compounds.
2. Silicate ceramics, which includes materials such as faience, porcelain, brick and products based on them. These components are used in medicine, in the manufacture of dishes, decorative ornaments, household items, in construction and other household areas of human activity.
3. Silicone compounds - silicones, silica gels, silicone oils.
4. Silicate glue - used as stationery, in pyrotechnics and construction.

Silicon, the price of which varies on the world market, but does not crossfrom top to bottom, the mark of 100 rubles of the Russian Federation per kilogram (per crystalline), is a sought-after and valuable substance. Naturally, compounds of this element are also widespread and applicable.

The biological role of silicon

From the point of view of significance for the body, silicon is important. Its content and tissue distribution is as follows:

• 0, 002% - muscular;
• 0, 000017% - bone;
• blood - 3.9 mg/l.

Every day, about one gram of silicon should get inside, otherwise diseases will begin to develop. There are no deadly among them, however, prolonged silicon starvation leads to:

• hair loss;
• appearance of acne and pimples;
• fragility and fragility of bones;
• easy capillary permeability;
• fatigue and headaches;
• the appearance of numerous bruises and bruises.

For plants, silicon is an important trace element necessary for normal growth and development. Animal experiments have shown that individuals who consume enough silicon daily grow best.