Silicon: application, chemical and physical properties

One of the most common elements in nature - it is silicium, or silicon.This wide distribution indicates the importance and significance of this matter.It is quickly understood and learned people who learned how to exploit the silicon.Its use is based on the special properties of which we'll talk further.

Silicon - a chemical element

If you give a description of this item on the situation in the periodic table, it is possible to designate the following important points:

  1. serial number - 14.
  2. period - the third guy.
  3. Group - IV.
  4. subgroup - the main.
  5. structure of the outer electron shell is given by 3s23p2.
  6. silicon element is a chemical symbol Si, which is pronounced "Silicium".
  7. oxidation state which it exhibits: -4;2;4.
  8. valence of an atom is equal to IV.
  9. atomic mass of silicon is equal to 28.086.
  10. In nature there are three stable isotopes of the element with mass numbers 28, 29 and 30.

Thus, a silicon atom from a chemical point of view - just studied the elements described a variety of d

ifferent properties.

History of discovery

Since the very nature of popular and mass content is different compounds of the element, since ancient times, people used to know about the properties and the names of many of them.Pure silicon is long remained beyond the bounds of human knowledge in chemistry.

most popular compounds that were used in everyday life and industry people of ancient cultures (Egyptians, Romans, Chinese, ancient Russians, Persians and others) were precious and semi-precious stones based on silicon oxide.These include:

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

also made use of old quartz and quartz sand in the construction business.However, the elemental silicon remained unsolved until the XIX century, although many scientists have tried in vain to distinguish it from different compounds, using and catalysts, and high temperatures, and even electricity.These are the bright minds as:

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

carry out successfully obtain silicon in a pure form succeeded Jens Jacobs Berzelius in 1823.For this, he conducted experiments on fused silica and fluoride vapor potassium metal.As a result, an amorphous modification of the element.The same scientist was invited to open the Latin name for the atom.

Still later, in 1855, another scientist - Sainte-Claire Deville - managed to synthesize a variety of different allotropes - crystalline silicon.Since knowledge of this element and its properties have become very quickly replenished.People have realized that it has unique features that could very well be used to meet their own needs.Therefore, today one of the most popular elements in electronics and technology - is silicon.Applying it only expands its borders every year.

atom gave the name of the Russian scientist Hess in 1831.That's it stuck to this day.

Content

in nature in terms of natural silicon is second only to oxygen.Its percentage in comparison with other atoms in the composition of the crust - 29.5%.In addition, carbon and silicon - two specific elements capable of configuring circuit, connecting with each other.That is why for the last are more than 400 different natural minerals, as part of which he found in the lithosphere, hydrosphere and biomass.

Where exactly is contained silicon?

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

can designate some of the most common minerals and rocks, a part of which is present in a large number of silicon.Chemistry them is such that the weight content of pure element therein reaches 75%.However, the specific number depends on the kind of material.So, rocks and minerals containing silicon:

  • feldspars;
  • mica;
  • amphibole;
  • disgrace;
  • chalcedony;
  • silicates;
  • sandstones;
  • aluminum silicates;
  • clay and others.

Accumulating in shells and exoskeletons of marine animals, silicon forms a potent with time deposits of silica on the bottom of ponds.This is one of the natural sources of this element.

Furthermore, it was found that Silicium may exist in pure native form - in the form of crystals.But such deposits are very rare.

physical properties of silicon

If you give a characterization of the element of the set of physical and chemical properties, first of all it is necessary to designate the physical parameters.Here are a few basic:

  1. exists in two allotropic modifications - amorphous and crystalline, which differ in all properties.
  2. Crystalline very similar to that of diamond, because carbon and silicon in this respect are virtually identical.However, the distance between the atoms of different (from silicon more), so the diamond is much harder and more durable.Type of lattice - face-centered cubic.
  3. substance is very brittle at high temperatures becomes pliable.
  4. The melting point is 1415˚S.
  5. Boiling point - 3250˚S.
  6. matter density - 2.33 g / cm3.
  7. color compounds - silver gray, expressed the characteristic metallic luster.
  8. has good semiconducting properties, which are able to be varied with the addition of certain agents.
  9. not soluble in water, organic solvents and acids.
  10. Specifically soluble in alkalis.

representation of physical properties of silicon allow people to manage it, and used to create a variety of products.For example, based on the properties semiconductivity use in electronics grade silicon.

Chemical properties Chemical properties of silicon are very dependent on the reaction conditions.If we talk about the pure substance at standard settings, you need to designate a very low activity.Both crystalline and amorphous silicon are very inert.Do not interact with any strong oxidizing agents (other than fluorine) or with strong reducing agents.

This is due to the fact that the surface of the material immediately formed oxide film SiO2, which hinders further cooperation.It is able to be formed under the influence of water, air and vapors.

If you change the standard terms and conditions and make heating the silicon to a temperature above 400˚S, its reactivity is strongly increased.In this case, it will react with:

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

At higher temperatures, the formation of products by reaction with boron, nitrogen and carbon.Of particular importance is the silicon carbide - SiC, since it is a good abrasive.

chemical properties of silicon are also clearly seen in reactions with metals.According to them it is an oxidizer, so the products are called silicide.It is known for such compounds:

  • alkaline;
  • alkaline;
  • transition metals.

Unusual properties has a compound obtained by alloying of iron and silicon.It bears the name of ferrosilicon ceramics and successfully applied in the industry.

With complex substances reacting silicon does not come, so all of their species is capable of dissolving only:

  • aqua regia (a mixture of nitric and hydrochloric acids);
  • caustic alkalis.

The temperature of the solution should not be less than 60 ° C.All this confirms a physical basis of substance - diamond-stable crystal lattice, giving it strength and inertia.

Methods for producing

of silicon in its purest form - the process is fairly expensive cost.Furthermore, by virtue of its properties either method gives only 90-99% pure product as an impurity in the form of metal and carbon remain still.So just to get enough material.It should also qualitatively clear of foreign elements.

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

  1. of white sand, which is a pure silica SiO2.After heating it with active metals (usually magnesium) is formed as a free element in the amorphous modification.The purity of this method is high, the product is obtained with a yield of 99.9 percent.
  2. more common method on an industrial scale - a sintering melt sand with coke in specialized thermal kilns.This method was developed by Russian scientists NN Beketov

Further treatment is exposure to products cleaning methods.For this purpose, acids or halogens (chloro, fluoro).

Amorphous silicon

Feature silicon would be incomplete if you do not consider separately each of its allotropic modifications.The first of them - is amorphous.In this state, we are examining the substance is a powder brown-brown, fine.Is highly hygroscopic, it exhibits a sufficiently high reactivity upon heating.Under standard conditions, is able to communicate only with strong oxidizing agents - fluorine.

Call it a kind of amorphous silicon crystal is not entirely correct.Its grille indicates that the substance - it is only a form of fine silicon existing in the form of crystals.Therefore, as such these modifications - the same compound.

However, their properties vary, so to say about allotropy.By itself, the amorphous silicon has a high ability svetopoglotitelnoy.In addition, under certain circumstances, this indicator is much faster than from a similar crystalline form.Therefore, it is used for technical purposes.In this form (powder) compound is easily applied to any surface, whether it is plastic or glass.Therefore, it is convenient to use amorphous silicon.The application is based on the manufacture of solar batteries of various sizes.

Although this type of battery wear pretty fast, due to the abrasion of the thin film material, but the use of and demand is only growing.Even in a short lifetime of solar cells based on amorphous silicon are able to provide energy to the entire enterprise.Besides the production of such material without waste, which makes it very economical.

such modification obtained by reduction of compounds of active metals, e.g., sodium or magnesium.

Crystalline silicon

silver-gray brilliant modification of the element.It is this form is the most common and most popular.This is due to a set of high-quality properties that have the substance.

Feature silicon crystal lattice includes the classification of its species, as several of them:

  1. electronic quality - the purest and most high quality.This is the kind used in electronics to build highly sensitive instruments.
  2. solar grade.The name itself defines the area of ​​use.It is also quite high purity silicon, the use of which is necessary to create a high-quality and long-running solar panels.Photoelectric converters that are based on precisely the crystal structure, better and more wear-resistant than those made using the amorphous modification by spraying on various types of substrate.
  3. of silicon.In this kind of substances included those samples, which contain about 98% pure element.The rest goes to various types of impurities:
  • boron;
  • aluminum;
  • chlorine;
  • carbon;
  • phosphorus and others.

Last variety of the substance in question is used to produce polycrystalline silicon.To carry out the process of recrystallization.As a result, the purity of such products are obtained, which can belong to the group of solar and electronic quality.

By nature polysilicon - is an intermediate between amorphous and crystalline modification.With this option is easier to work, it is better to be recyclable and cleaning fluorine and chlorine.

products that result can be categorized as:

  • multisilicon;
  • single crystal;
  • shaped crystals;
  • silicon scrap;
  • technical silicon;
  • waste products in the form of fragments and scraps of material.

Each one of them is used in industry and is used by a person completely.Therefore, the production processes related to silicon, are considered to be zero waste.This significantly reduces its economic cost, while not affecting the quality.

use of pure silicon

production of silicon in the industry is well established, and its scale is quite bulky.This is due to the fact that this element is clean, and in the form of different compounds, is widespread and demand in the various fields of science and technology.

Where is using crystalline and amorphous silicon in its purest form?

  1. In metallurgy as an alloying addition, the ability to change the properties of metals and their alloys.Thus, it is used in the smelting of steel and cast iron.
  2. Different kinds of stuff goes on manufacturing cleaner option - polysilicon.
  3. compounds of silicon with organic substances - is a chemical industry, which was particularly popular today.Organosilicon materials are used in medicine, in the manufacture of utensils, instruments and more.
  4. Production of various solar cells.This method of energy production is one of the most promising in the future.Eco-friendly, cost-effective and hardwearing - the main advantages of such electricity.
  5. Silicon lighters used for a long time.Even in ancient times people used the flint spark for the ignition of fire.This principle is the basis for the production of various kinds of lighters.Today, there are species in which the flint is replaced by an alloy of definite composition, giving even more rapid results (arcing).
  6. Electronics and solar power.
  7. Manufacturing zerkalets in gas laser devices.

Thus, pure silicon has a lot of advantageous and special features that enable to use it to create important and relevant products.

The use of silicon compounds

addition of a simple substance is used and various compounds of silicon, and very widely.There is an entire industry, called silicate.It is based on the use of various substances, which include this awesome item.What is the connection, and that are produced?

  1. quartz or river sand - SiO2.Used for making such decorative and building materials such as cement and glass.Where are these materials is well known.No construction is not complete without these components, which confirms the importance of silicon compounds.
  2. Silicate ceramics, which includes materials such as earthenware, porcelain, brick and products based on them.These components are used in medicine, in the manufacture of tableware, decorations, household items, construction and other residential areas of human activity.
  3. Silicones - silicones, silica, silicone oil.