Silicon name. Chemical properties of silicon
CPU? Sand? What associations do you have with this word? Or maybe Silicon Valley?
Be that as it may, we come across silicon every day, and if you are interested in finding out what Si is and what it is eaten with, please refer to the cat.
Introduction
As a student at one of the Moscow universities, with a specialty in Nanomaterials, I wanted to introduce you, dear reader, to the most important chemical elements of our planet. I spent a long time choosing where to start, carbon or silicon, and still decided to stop at Si, because the heart of any modern gadget is based on it, so to speak, of course. I will try to express my thoughts in an extremely simple and accessible way. By writing this material, I was counting mainly on beginners, but more advanced people will also be able to learn something interesting. I would also like to say that the article was written solely to broaden the horizons of those interested. And so let's get started.
Silicium
Silicon (lat. Silicium), Si, chemical element Group IV of Mendeleev's periodic system; atomic number 14, atomic mass 28.086.
In nature, the element is represented by three stable isotopes: 28Si (92.27%), 29Si (4.68%) and 30Si (3.05%).
Density (at no.) 2.33 g/cm?
Melting point 1688 K
Powder Si
Historical reference
Silicon compounds, widespread on earth, have been known to man since the Stone Age. The use of stone tools for labor and hunting continued for several millennia. The use of Silicon compounds associated with their processing - glass production - began around 3000 BC. e. (V Ancient Egypt). The earliest known Silicon compound is SiO2 oxide (silica). In the 18th century, silica was considered a simple solid and classified as an “earth” (as reflected in its name). The complexity of the composition of silica was established by I. Ya. Berzelius. For the first time, in 1825, he obtained elemental silicon from silicon fluoride SiF4, reducing the latter with potassium metal. The new element was given the name “silicon” (from the Latin silex - flint). Russian name introduced by G. I. Hess in 1834.
Silicon is very common in nature as part of ordinary sand.
Distribution of Silicon in nature
Silicon is the second most abundant element in the earth's crust (after oxygen), its average content in the lithosphere is 29.5% (by mass). In the earth's crust, Silicon plays the same primary role as carbon in animals and flora. For the geochemistry of silicon, its extremely strong connection with oxygen is important. About 12% of the lithosphere is silica SiO2 in the form of the mineral quartz and its varieties. 75% of the lithosphere is composed of various silicates and aluminosilicates (feldspars, micas, amphiboles, etc.). The total number of minerals containing silica exceeds 400.
Physical properties of Silicon
I think there is no point in dwelling here, all physical properties are freely available, but I will list the most basic ones.
Boiling point 2600 °C
Silicon is transparent to long-wave infrared rays
Dielectric constant 11.7
Silicon Mohs hardness 7.0
I would like to say that silicon is a brittle material; noticeable plastic deformation begins at temperatures above 800°C.
Silicon is a semiconductor, which is why it is widely used. The electrical properties of silicon are very dependent on impurities.
Chemical properties of Silicon
There’s a lot that could be said here, of course, but I’ll focus on the most interesting. In Si compounds (similar to carbon) 4-valentene.
In air, silicon is stable even at elevated temperatures due to the formation of a protective oxide film. In oxygen it oxidizes starting at 400 °C, forming silicon oxide (IV) SiO2.
Silicon is resistant to acids and dissolves only in a mixture of nitric and hydrofluoric acids, and easily dissolves in hot alkali solutions with the release of hydrogen.
Silicon forms 2 groups of oxygen-containing silanes - siloxanes and siloxenes. Silicon reacts with nitrogen at temperatures above 1000 °C. Of great practical importance is the nitride Si3N4, which does not oxidize in air even at 1200 °C, is resistant to acids (except nitric) and alkalis, as well as to molten metals and slags, which makes it is a valuable material for the chemical industry, as well as for the production of refractories. Silicon compounds with carbon (silicon carbide SiC) and boron (SiB3, SiB6, SiB12) are characterized by high hardness, as well as thermal and chemical resistance.
Obtaining Silicon
I think this is the most interesting part, let’s take a closer look here.
Depending on the purpose there are:
1.
Electronic quality silicon(so-called “electronic silicon”) - the highest quality silicon with a silicon content of over 99.999% by weight, the electrical resistivity of electronic quality silicon can be in the range from approximately 0.001 to 150 Ohm cm, but the resistance value must be ensured exclusively a given impurity, i.e., the entry of other impurities into the crystal, even if they provide a given electrical resistivity, is, as a rule, unacceptable.
2.
Solar grade silicon(so-called “solar silicon”) - silicon with a silicon content of over 99.99% by weight, used for the production of photovoltaic converters (solar batteries).
3.
Technical silicon- silicon blocks of polycrystalline structure obtained by carbothermic reduction from pure quartz sand; contains 98% silicon, the main impurity is carbon, characterized by a high content of alloying elements - boron, phosphorus, aluminum; mainly used to produce polycrystalline silicon.
Technical purity silicon (95-98%) is obtained in an electric arc by reducing silica SiO2 between graphite electrodes. In connection with the development of semiconductor technology, methods have been developed for producing pure and highly pure silicon. This requires the preliminary synthesis of the purest initial silicon compounds, from which silicon is extracted by reduction or thermal decomposition.
Polycrystalline silicon (“polysilicon”) is the purest form of industrially produced silicon - a semi-finished product obtained by purifying technical silicon using chloride and fluoride methods and used for the production of mono- and multicrystalline silicon.
Traditionally, polycrystalline silicon is obtained from technical silicon by converting it into volatile silanes (monosilane, chlorosilanes, fluorosilanes) with subsequent separation of the resulting silanes, rectification purification of the selected silane and reduction of the silane to metallic silicon.
Pure semiconductor silicon is obtained in two forms: polycrystalline(reduction of SiCl4 or SiHCl3 with zinc or hydrogen, thermal decomposition of SiI4 and SiH4) and monocrystalline(crucible-free zone melting and “pulling” a single crystal from molten silicon - Czochralski method).
Here you can see the process of growing silicon using the Czochralski method.
Czochralski method- a method of growing crystals by pulling them upward from the free surface of a large volume of melt with the initiation of crystallization by bringing a seed crystal (or several crystals) of a given structure and crystallographic orientation into contact with the free surface of the melt.
Application of Silicon
Specially doped silicon is widely used as a material for the manufacture of semiconductor devices (transistors, thermistors, power rectifiers, thyristors; solar photocells used in spaceships, as well as a lot of other things).
Since silicon is transparent to rays with wavelengths from 1 to 9 microns, it is used in infrared optics.
Silicon has diverse and expanding applications. In metallurgy Si
used to remove oxygen dissolved in molten metals (deoxidation).
Silicon is a component of a large number of alloys of iron and non-ferrous metals.
Typically, Silicon gives alloys increased resistance to corrosion, improves their casting properties and increases mechanical strength; however, at higher levels Silicon can cause brittleness.
The most important are iron, copper and aluminum alloys containing silicon.
Silica is processed by glass, cement, ceramics, electrical and other industries.
Ultra-pure silicon is primarily used for the production of single electronic devices (for example, your computer processor) and single-chip microcircuits.
Pure silicon, ultra-pure silicon waste, purified metallurgical silicon in the form of crystalline silicon are the main raw materials for solar energy.
Monocrystalline silicon - in addition to electronics and solar energy, is used to make gas laser mirrors.
Ultrapure silicon and its products
Silicon in the body
Silicon is found in the body in the form of various compounds, mainly involved in the formation of hard skeletal parts and tissues. Some marine plants (for example, diatoms) and animals (for example, siliceous sponges, radiolarians) can accumulate especially large amounts of silicon, forming thick deposits of silicon (IV) oxide when they die on the ocean floor. In cold seas and lakes, biogenic silts enriched with silicon predominate; in tropical seas, calcareous silts with a low silicon content predominate. Among terrestrial plants, cereals, sedges, palm trees, and horsetails accumulate a lot of silicon. In vertebrates, the content of silicon (IV) oxide in ash substances is 0.1-0.5%. Silicon is found in the largest quantities in dense connective tissue, kidneys, and pancreas. The daily human diet contains up to 1 g of silicon. When there is a high content of silicon (IV) oxide dust in the air, it enters the human lungs and causes the disease silicosis.
Conclusion
Well, that's all, if you read to the end and delve a little deeper, then you are one step closer to success. I hope I didn’t write in vain and at least someone liked the post. Thank you for your attention.
>> Chemistry: Silicon and its compounds
The second representative of the elements of the main subgroup of group IV is silicon Si.
In nature silicon- the second most common chemical element after oxygen. More than a quarter of the earth's crust consists of its compounds. The most common silicon compound is its dioxide SiO2, another name is silica. In nature, it forms the mineral quartz (Fig. 46) and many varieties, such as rock crystal and its famous purple form - amethyst, as well as agate, opal, jasper, chalcedony, carnelian, which are known as ornamental and semi-precious stones. Silicon dioxide is also common and quartz sand.
From varieties of minerals based on silicon dioxide - flint, chalcedony and others primitive people made tools. It was flint, this inconspicuous and not very durable stone, that laid the foundation stone age- the age of flint tools. There are two reasons for this: the prevalence and availability of flint, as well as its ability to form sharp cutting edges when chipped.
Rice. 46. Natural quartz crystal (left) and artificially grown (right)
The second type of natural silicon compounds is silicates. Among them, the most common are aluminosilicates (it is clear that these silicates contain aluminum). Aluminosilicates include granite, different kinds clay, mica. A silicate that does not contain aluminum is, for example, asbestos.
The most important silicon compound- SiO2 oxide is necessary for the life of plants and animals. It gives strength to plant stems and protective coverings of animals. Thanks to him, reeds, reeds and horsetails stand as strong as bayonets, sharp sedge leaves cut like knives, stubble in a mown field pricks like needles, and the stems of cereals are so strong that they do not allow the fields in the fields to lie down from rain and wind. Fish scales, insect shells, butterfly wings, bird feathers and animal fur are durable because they contain silica.
Silicon gives smoothness and strength to human bones.
Silicon is also part of lower living organisms - diatoms and radiolarians - the most delicate lumps of living matter that create their unsurpassedly beautiful skeletons from silica.
Properties of silicon.
If you use a solar-powered calculator, you're probably familiar with crystalline silicon. This is a semiconductor. Unlike metals, its electrical conductivity increases with increasing temperature. Solar panels are installed on satellites, spacecraft and stations, converting solar energy into electrical energy. They use semiconductor crystals, primarily silicon.
Silicon solar cells can convert up to 10% of absorbed solar energy into electricity.
Silicon burns in oxygen, forming the already known silicon dioxide, or silicon oxide (1U):
Being a non-metal, when heated it combines with metals to form silicides, for example:
Si + 2Mg = Mg2 Si
Silicides are easily decomposed by water or acids, releasing a gaseous hydrogen compound of silicon - silane:
Mg2 Si + 2H2SO4 = 2MgSO4 + SiH4
Unlike hydrocarbons, silane spontaneously ignites in air and burns to form silicon dioxide and water:
SiH4 + 202 = SiO2 + 2H2O
The increased reactivity of silane compared to methane CH4 is explained by the fact that silicon larger size atom than carbon, so -H chemical bonds are weaker than C-H bonds.
Silicon reacts with concentrated aqueous solutions of alkalis, forming silicates and hydrogen:
Si + 2NaOH + H20 = Na2SiO3 + 2H2
Silicon is obtained by reducing it from dioxide with magnesium or carbon.
Silicon(IV) oxide, or silicon dioxide, or silica, like CO2, is an acidic oxide. However, unlike CO2, it has not a molecular, but an atomic crystal lattice. Therefore, SiO2 is a hard and refractory substance. It does not dissolve in water and acids, except, as you know, hydrofluoric acid, but it reacts at high temperatures with alkalis to form silicic acid salts - silicates.
Silicates can also be obtained by fusing silicon dioxide with metal oxides or carbonates:
SiO2 + CaO = CaSiO3
SiO2 + CaC03 = CaSiO3 + C02
Sodium and potassium silicates are called soluble glass. Their aqueous solutions are the well-known silicate glue.
From solutions of silicates, by the action of stronger acids on them - hydrochloric, sulfuric, acetic and even carbonic, silicic acid H2SiO3 is obtained:
K2SiO3 + 2HCl = 2КCl + Н2SiO3
Therefore, H2SiO3 is a very weak acid. It is insoluble in water and falls out of the reaction mixture in the form of a gelatinous precipitate, sometimes compactly filling the entire volume of the solution, turning it into a semi-solid mass similar to jelly or jelly. When this mass dries, a highly porous substance is formed - silica gel, which is widely used as an adsorbent - an absorber of other substances.
Application of silicon. You already know that silicon is used to produce semiconductor materials, as well as acid-resistant alloys. When quartz sand is fused with coal at high temperatures, silicon carbide SiC is formed, which is second only to diamond in hardness. Therefore, it is used for sharpening the cutters of metal-cutting machines and polishing precious stones.
Various quartz chemical glassware are made from molten quartz, which can withstand high temperatures and do not crack when subjected to sudden cooling.
Silicon compounds serve as the basis for the production of glass and cement.
Regular window glass has a composition that can be expressed by the formula
Na20 CaO 6SiO2
It is produced in special glass furnaces by fusing a mixture of soda, limestone and sand.
A distinctive feature of glass is the ability to soften and, in a molten state, take any shape that is preserved when the glass hardens. The production of tableware and other glass products is based on this.
Glass is one of the oldest inventions of mankind. Already 3-4 thousand years ago, glass production was developed in Egypt, Syria, Phenicia and the Black Sea region. Masters have reached high perfection in glassmaking Ancient Rome. They knew how to obtain colored glass and make mosaics from pieces of such glass.
Glass is a material not only for craftsmen, but also for artists. Glass works of art are a must-have attribute of any major museum. And the stained glass windows of churches and mosaic panels are vivid examples of this. In one of the premises of the St. Petersburg branch Russian Academy Sciences there is a mosaic portrait of Peter I, made by M. V. Lomonosov.
Various additives give additional qualities to glass. Thus, by introducing lead oxide, crystal glass is obtained, chromium oxide colors the glass in green color, cobalt oxide - blue, etc.
The areas of application of glass are very extensive. This is window, bottle, lamp, mirror glass; optical glass - from glasses glasses to camera glasses; lenses of countless optical instruments - from microscopes to telescopes.
Another important material obtained from silicon compounds is cement. It is obtained by sintering clay and limestone in special rotary kilns. If cement powder is mixed with water, a cement paste is formed, or, as builders call it, a “mortar” that gradually hardens. When sand or crushed stone is added to cement as a filler, concrete is obtained. The strength of concrete increases if an iron frame is introduced into it - reinforced concrete is obtained, from which wall panels, floor blocks, bridge trusses, etc. are prepared.
The silicate industry produces glass and cement. It also produces silicate ceramics - brick, porcelain, earthenware and products made from them.
Discovery of silicon . Although already in ancient times people widely used silicon compounds in their everyday life, silicon itself in the elemental state was first obtained in 1825 by the Swedish chemist J. Ya. Berzelius. However, 12 years before him, silicon was obtained by J. Gay-Lussac and L. Thénard, but it was very contaminated with impurities.
The Latin name silicium originates from lat. silex - flint. The Russian name “silicon” comes from the Greek. kremnos - cliff, rock.
1. Natural silicon compounds: silica, quartz and its varieties, silicates, aluminosilicates, asbestos.
2. Biological significance silicon
3. Properties of silicon: semiconductor, interaction with oxygen, metals, alkalis.
5. Silicon(IV) oxide. Its structure and properties: interaction with alkalis, basic oxides, carbonates and magnesium.
6. Silicic acid and its salts. Soluble glass.
7. Application of silicon and its compounds.
8. Glass.
9. Cement.
Indicate the similarities and differences between carbon(IV) oxide and silicon(IV) oxide in structure and properties (interaction with water, alkalis, basic oxides and magnesium). Write the reaction equations.
Why is carbon called the main element of living nature, and silicon - the main element of inanimate nature?
When an excess sodium hydroxide solution reacted with 16 g of silicon, 22.4 liters of hydrogen were obtained. What is the mass fraction of silicon in the sample taken? How many grams of silicon oxide did it contain? How many grams of 60% alkali solution were required for the reaction?
Write the reaction equations that can be used to carry out the following transformations:
a) SiO2 -> Si -> Ca2Si -> SiH4 -> SiO2 -> Si
b) Si -> SiO2 -> Na2SiO3 -> H2SiO3 -> SiO2 -> Si
Consider oxidation-reduction processes.
The famous scientist in the field of mineralogy A.E. Fersman wrote: “They show a wide variety of objects: a transparent ball sparkling in the sun with the purity of cold spring water, a beautiful, variegated agate, a bright play of multi-colored opal, clean sand on the seashore, as thin as silk. , a thread of fused quartz or heat-resistant dishes made from it, beautifully cut piles of rock crystal, a mysterious design of fantastic jasper, petrified wood turned into stone, a roughly processed arrowhead of an ancient man... all this is one and the same compound...” ? Complete the quote.
Lesson content lesson notes supporting frame lesson presentation acceleration methods interactive technologies Practice tasks and exercises self-test workshops, trainings, cases, quests homework discussion questions rhetorical questions from students Illustrations audio, video clips and multimedia photographs, pictures, graphics, tables, diagrams, humor, anecdotes, jokes, comics, parables, sayings, crosswords, quotes Add-ons abstracts articles tricks for the curious cribs textbooks basic and additional dictionary of terms other Improving textbooks and lessonscorrecting errors in the textbook updating a fragment in a textbook, elements of innovation in the lesson, replacing outdated knowledge with new ones Only for teachers perfect lessons calendar plan for the year guidelines discussion programs Integrated LessonsAs an independent chemical element, silicon became known to mankind only in 1825. Which, of course, did not prevent the use of silicon compounds in so many areas that it is easier to list those where the element is not used. This article will shed light on the physical, mechanical and useful chemical properties of silicon and its compounds, applications, and we will also talk about how silicon affects the properties of steel and other metals.
First, let's look at general characteristics silicon From 27.6 to 29.5% of the mass of the earth's crust is silicon. IN sea water the concentration of the element is also considerable – up to 3 mg/l.
In terms of abundance in the lithosphere, silicon ranks second after oxygen. However, its most famous form, silica, is an dioxide, and it is its properties that have become the basis for such widespread use.
This video will tell you what silicon is:
Concept and features
Silicon is a non-metal, but under different conditions it can exhibit both acidic and basic properties. It is a typical semiconductor and is extremely widely used in electrical engineering. Its physical and chemical properties are largely determined by its allotropic state. Most often they deal with the crystalline form, since its qualities are more in demand in the national economy.
- Silicon is one of the basic macroelements in the human body. Its deficiency has a detrimental effect on the condition of bone tissue, hair, skin, and nails. In addition, silicon affects the performance of the immune system.
- In medicine, the element, or rather its compounds, found their first application precisely in this capacity. Water from wells lined with silicon was not only clean, but also had a positive effect on resistance to infectious diseases. Today, compounds with silicon serve as the basis for drugs against tuberculosis, atherosclerosis, and arthritis.
- In general, the nonmetal is low-active, but it is difficult to find it in its pure form. This is due to the fact that in air it is quickly passivated by a layer of dioxide and stops reacting. When heated, chemical activity increases. As a result, humanity is much more familiar with the compounds of matter, rather than with itself.
Thus, silicon forms alloys with almost all metals - silicides. All of them are characterized by refractoriness and hardness and are used in appropriate areas: gas turbines, furnace heaters.
The non-metal is placed in D.I. Mendeleev’s table in group 6 along with carbon and germanium, which indicates a certain commonality with these substances. Thus, what it has in common with carbon is its ability to form organic-type compounds. At the same time, silicon, like germanium, can exhibit the properties of a metal in some chemical reactions, which is used in synthesis.
Advantages and disadvantages
Like any other substance from the point of view of use in the national economy, silicon has certain useful or not very useful qualities. They are important precisely for determining the area of use.
- A significant advantage of the substance is its availability. In nature, it is true that it is not found in free form, but still, the technology for producing silicon is not so complicated, although it is energy-consuming.
- The second most important advantage is formation of many compounds with unusually beneficial properties. These include silanes, silicides, dioxide, and, of course, a wide variety of silicates. The ability of silicon and its compounds to form complex solid solutions is almost infinite, which makes it possible to endlessly obtain a wide variety of variations of glass, stone and ceramics.
- Semiconductor properties non-metal provides it with a place as a base material in electrical and radio engineering.
- Non-metal is non-toxic, which allows for use in any industry, and at the same time does not turn the technological process into a potentially dangerous one.
The disadvantages of the material include only relative fragility with good hardness. Silicon is not used for load-bearing structures, but this combination allows the surface of the crystals to be properly processed, which is important for instrument making.
Let's now talk about the basic properties of silicon.
Properties and characteristics
Since crystalline silicon is most often used in industry, it is its properties that are more important, and it is they that are given in technical specifications. The physical properties of the substance are as follows:
- melting point – 1417 C;
- boiling point – 2600 C;
- density is 2.33 g/cu. cm, which indicates fragility;
- heat capacity, as well as thermal conductivity, are not constant even on the purest samples: 800 J/(kg K), or 0.191 cal/(g deg) and 84-126 W/(m K), or 0.20-0, 30 cal/(cm·sec·deg) respectively;
- transparent to long-wave infrared radiation, which is used in infrared optics;
- dielectric constant – 1.17;
- hardness on the Mohs scale – 7.
The electrical properties of a nonmetal are highly dependent on impurities. In industry, this feature is used by modulating the desired type of semiconductor. At normal temperatures, silicon is brittle, but when heated above 800 C, plastic deformation is possible.
The properties of amorphous silicon are strikingly different: it is highly hygroscopic and reacts much more actively even at normal temperatures.
The structure and chemical composition, as well as the properties of silicon are discussed in the video below:
Composition and structure
Silicon exists in two allotropic forms, which are equally stable at normal temperatures.
- Crystal has the appearance of a dark gray powder. The substance, although it has a diamond-like crystal lattice, is fragile due to the excessively long bonds between the atoms. Of interest are its semiconductor properties.
- At very high pressures you can get hexagonal modification with a density of 2.55 g/cu. cm. However, this phase has not yet found practical significance.
- Amorphous– brown-brown powder. Unlike the crystalline form, it reacts much more actively. This is due not so much to the inertness of the first form, but to the fact that in air the substance is covered with a layer of dioxide.
In addition, it is necessary to take into account another type of classification related to the size of the silicon crystal, which together form the substance. A crystal lattice, as is known, presupposes order not only of atoms, but also of the structures that these atoms form - the so-called long-range order. The larger it is, the more homogeneous the substance will be in properties.
- Monocrystalline– the sample is one crystal. Its structure is maximally ordered, its properties are homogeneous and well predictable. This is the material that is most in demand in electrical engineering. However, it is also one of the most expensive species, since the process of obtaining it is complex and the growth rate is low.
- Multicrystalline– the sample consists of a number of large crystalline grains. The boundaries between them form additional defect levels, which reduces the performance of the sample as a semiconductor and leads to faster wear. The technology for growing multicrystals is simpler, and therefore the material is cheaper.
- Polycrystalline- comprises large quantity grains located randomly relative to each other. This is the purest type of industrial silicon, used in microelectronics and solar energy. Quite often used as a raw material for growing multi- and single crystals.
- Amorphous silicon also occupies a separate position in this classification. Here the order of the atoms is maintained only at the shortest distances. However, in electrical engineering it is still used in the form of thin films.
Non-metal production
Obtaining pure silicon is not so easy, given the inertness of its compounds and the high melting point of most of them. In industry, they most often resort to reduction with carbon from dioxide. The reaction is carried out in arc furnaces at a temperature of 1800 C. In this way, a non-metal with a purity of 99.9% is obtained, which is not enough for its use.
The resulting material is chlorinated to produce chlorides and hydrochlorides. Then the compounds are purified by all possible methods from impurities and reduced with hydrogen.
The substance can also be purified by obtaining magnesium silicide. The silicide is exposed to hydrochloric or acetic acid. Silane is obtained and the latter is purified different ways– sorption, rectification and so on. Then the silane is decomposed into hydrogen and silicon at a temperature of 1000 C. In this case, a substance is obtained with an impurity fraction of 10 -8 -10 -6%.
Application of the substance
For industry, the electrophysical characteristics of a nonmetal are of greatest interest. Its single crystal form is an indirect gap semiconductor. Its properties are determined by impurities, which makes it possible to obtain silicon crystals with specified properties. Thus, the addition of boron and indium makes it possible to grow a crystal with hole conductivity, and the introduction of phosphorus or arsenic makes it possible to grow a crystal with electronic conductivity.
- Silicon literally serves as the basis of modern electrical engineering. Transistors, photocells, integrated circuits, diodes, and so on are made from it. Moreover, the functionality of the device is almost always determined only by the near-surface layer of the crystal, which determines very specific requirements for surface treatment.
- In metallurgy, technical silicon is used both as an alloy modifier - it gives greater strength, and as a component - in, for example, and as a deoxidizing agent - in the production of cast iron.
- Ultrapure and purified metallurgical materials form the basis of solar energy.
- Nonmetallic dioxide occurs in nature in many different forms. Its crystal varieties - opal, agate, carnelian, amethyst, rock crystal - have found their place in jewelry. Modifications that are not so attractive in appearance - flint, quartz - are used in metallurgy, construction, and radio-electronics.
- A compound of a non-metal with carbon, carbide, is used in metallurgy, instrument making, and the chemical industry. It is a wide-band semiconductor, characterized by high hardness - 7 on the Mohs scale, and strength, which allows it to be used as an abrasive material.
- Silicates - that is, salts of silicic acid. Unstable, easily decomposes under the influence of temperature. Their remarkable feature is that they form numerous and varied salts. But the latter are the basis for the production of glass, ceramics, earthenware, crystal, etc. We can safely say that modern construction is based on a variety of silicates.
- Glass represents the most interesting case here. Its basis is aluminosilicates, but insignificant admixtures of other substances - usually oxides - give the material a lot of different properties, including color. -, earthenware, porcelain, in fact, has the same formula, although with a different ratio of components, and its diversity is also amazing.
- The non-metal has one more ability: it forms compounds like carbon ones, in the form of a long chain of silicon atoms. Such compounds are called organosilicon compounds. The scope of their application is no less well known - these are silicones, sealants, lubricants, and so on.
Silicon is a very common element and has an unusual great importance in many areas of the national economy. Moreover, not only the substance itself, but all its various and numerous compounds are actively used.
This video will tell you about the properties and uses of silicon:
Silicon in free form was isolated in 1811 by J. Gay-Lussac and L. Thénard by passing silicon fluoride vapor over metallic potassium, but it was not described by them as an element. The Swedish chemist J. Berzelius in 1823 gave a description of the silicon he obtained by treating the potassium salt K 2 SiF 6 with potassium metal at high temperature. The new element was given the name “silicon” (from the Latin silex - flint). The Russian name "silicon" was introduced in 1834 by the Russian chemist German Ivanovich Hess. Translated from ancient Greek. krhmnoz- "cliff, mountain."
Being in nature, receiving:
In nature, silicon is found in the form of dioxide and silicates of various compositions. Natural silica occurs primarily in the form of quartz, although other minerals such as cristobalite, tridymite, kitite, and cousite also exist. Amorphous silica is found in diatom deposits on the bottom of seas and oceans - these deposits were formed from SiO 2, which was part of diatoms and some ciliates.
Free silicon can be obtained by calcining fine white sand with magnesium, which in chemical composition is almost pure silicon oxide, SiO 2 +2Mg=2MgO+Si. In industry, technical grade silicon is obtained by reducing the SiO 2 melt with coke at a temperature of about 1800°C in arc furnaces. The purity of silicon obtained in this way can reach 99.9% (the main impurities are carbon and metals).
Physical properties:
Amorphous silicon has the form of a brown powder, the density of which is 2.0 g/cm 3 . Crystalline silicon is a dark gray, shiny crystalline substance, brittle and very hard, crystallizing in the diamond lattice. This is a typical semiconductor (it conducts electricity better than an insulator like rubber, and worse than a conductor like copper). Silicon is fragile; only when heated above 800 °C does it become a plastic substance. Interestingly, silicon is transparent to infrared radiation, starting at a wavelength of 1.1 micrometers.
Chemical properties:
Chemically, silicon is inactive. At room temperature it reacts only with fluorine gas, resulting in the formation of volatile silicon tetrafluoride SiF 4 . When heated to a temperature of 400-500 °C, silicon reacts with oxygen to form dioxide, and with chlorine, bromine and iodine to form the corresponding highly volatile tetrahalides SiHal 4. At a temperature of about 1000°C, silicon reacts with nitrogen to form the nitride Si 3 N 4, with boron - the thermally and chemically stable borides SiB 3, SiB 6 and SiB 12. Silicon does not react directly with hydrogen.
For silicon etching, a mixture of hydrofluoric and nitric acids is most widely used.
Silicon dissolves in hot alkali solutions: Si + 2KOH + H 2 O = K 2 SiO 3 + 2H 2
Silicon is characterized by compounds with an oxidation state of +4 or -4.
The most important connections:
Silicon dioxide, SiO 2- (silicon anhydride), colorless. christ. substance, refractory (1720 C), with high hardness. Acidic oxide, chemically inactive, interacts with hydrofluoric acid and alkali solutions, in the latter case forming salts of silicic acids - silicates. Silicates are also formed when silicon oxide fuses with alkalis, basic oxides and some salts
SiO 2 + 4NaOH = Na 4 SiO 4 + 2H 2 O; SiO 2 + CaO = CaSiO 3;
Na 2 CO 3 + CaCO 3 + 6SiO 2 = Na 2 CaSi 6 O 14 + 2CO 2 (mixed sodium-calcium silicate, glass)
Silicic acids- weak, insoluble, formed when acid is added to a silicate solution in the form of a gel (gelatin-like substance). H 4 SiO 4 (orthosilicon) and H 2 SiO 3 (metasilicon, or silicon) exist only in solution and are irreversibly converted to SiO 2 when heated and dried. The resulting solid porous product is silica gel, has a developed surface and is used as a gas adsorbent, desiccant, catalyst and catalyst carrier.
Silicates- salts of silicic acids for the most part (except for sodium and potassium silicates) are insoluble in water. Soluble silicates in solution undergo severe hydrolysis.
Hydrogen compounds- analogues of hydrocarbons, silanes, compounds in which silicon atoms are connected by a single bond, strong, if the silicon atoms are connected by a double bond. Like hydrocarbons, these compounds form chains and rings. All silanes can spontaneously ignite, form explosive mixtures with air and easily react with water: SiH 4 + 2H 2 O = SiO 2 + 4H 2
Silicon tetrafluoride SiF 4, a gas with an unpleasant odor, poisonous, is formed by the action of hydrofluoric acid on silicon and many of its compounds, including glass:
Na 2 SiO 3 + 6HF = 2NaF + SiF 4 + 3H 2 O
Reacts with water to form silicon and hexafluorosilicon(H 2 SiF 6) acids:
3SiF 4 + 3H 2 O = 2H 2 SiF 6 + H 2 SiO 2
H 2 SiF 6 is close in strength to sulfuric acid, the salts are fluorosilicates.
Application:
Silicon is most widely used in the production of alloys for imparting strength to aluminum, copper and magnesium and for the production of ferrosilicides, which are important in the production of steels and semiconductor technology. Silicon crystals are used in solar cells and semiconductor devices - transistors and diodes. Silicon also serves as a raw material for the production of organosilicon compounds, or siloxanes, obtained in the form of oils, lubricants, plastics and synthetic rubbers. Inorganic silicon compounds are used in ceramics and glass technology, as an insulating material and piezocrystals
For some organisms, silicon is an important biogenic element. It is part of the supporting structures in plants and skeletal structures in animals. Silicon is concentrated in large quantities by marine organisms - diatoms, radiolarians, sponges. Large amounts of silicon are concentrated in horsetails and cereals, primarily in the subfamilies of Bamboo and Rice, including rice. Human muscle tissue contains (1-2)·10 -2% silicon, bone tissue - 17·10 -4%, blood - 3.9 mg/l. Up to 1 g of silicon enters the human body with food every day.
Antonov S.M., Tomilin K.G.
HF Tyumen State University, 571 group.
Sources: Silicon Wikipedia; Silicon in the Online Encyclopedia "Around the World", ;
Silicon on site
CPU? Sand? What associations do you have with this word? Or maybe Silicon Valley?
Be that as it may, we come across silicon every day, and if you are interested in finding out what Si is and what it is eaten with, please refer to the cat.
Introduction
As a student at one of the Moscow universities with a specialty in Nanomaterials, I wanted to introduce you, dear reader, to the most important chemical elements of our planet. I spent a long time choosing where to start, carbon or silicon, and still decided to stop at Si, because the heart of any modern gadget is based on it, so to speak, of course. I will try to express my thoughts in an extremely simple and accessible way. By writing this material, I was counting mainly on beginners, but more advanced people will also be able to learn something interesting. I would also like to say that the article was written solely to broaden the horizons of those interested. So let's get started.Silicium
Silicon (lat. Silicium), Si, chemical element of group IV of the periodic system of Mendeleev; atomic number 14, atomic mass 28.086.In nature, the element is represented by three stable isotopes: 28Si (92.27%), 29Si (4.68%) and 30Si (3.05%).
Density (at no.) 2.33 g/cm³
Melting point 1688 K
Powder Si
Historical reference
Silicon compounds, widespread on earth, have been known to man since the Stone Age. The use of stone tools for labor and hunting continued for several millennia. The use of Silicon compounds associated with their processing - glass production - began around 3000 BC. e. (in Ancient Egypt). The earliest known Silicon compound is SiO2 oxide (silica). In the 18th century, silica was considered a simple solid and classified as an “earth” (as reflected in its name). The complexity of the composition of silica was established by I. Ya. Berzelius. For the first time, in 1825, he obtained elemental silicon from silicon fluoride SiF4, reducing the latter with potassium metal. The new element was given the name “silicon” (from the Latin silex - flint). The Russian name was introduced by G. I. Hess in 1834.
Silicon is very common in nature as part of ordinary sand.
Distribution of Silicon in nature
Silicon is the second most abundant element in the earth's crust (after oxygen), its average content in the lithosphere is 29.5% (by mass). In the earth's crust, Silicon plays the same primary role as carbon in the animal and plant world. For the geochemistry of silicon, its extremely strong connection with oxygen is important. About 12% of the lithosphere is silica SiO2 in the form of the mineral quartz and its varieties. 75% of the lithosphere is composed of various silicates and aluminosilicates (feldspars, micas, amphiboles, etc.). The total number of minerals containing silica exceeds 400.Physical properties of Silicon
I think there is no point in dwelling here, all physical properties are freely available, but I will list the most basic ones.Boiling point 2600 °C
Silicon is transparent to long-wave infrared rays
Dielectric constant 11.7
Silicon Mohs hardness 7.0
I would like to say that silicon is a brittle material; noticeable plastic deformation begins at temperatures above 800°C.
Silicon is a semiconductor, which is why it is widely used. The electrical properties of silicon are very dependent on impurities.
Chemical properties of Silicon
There’s a lot that could be said here, of course, but I’ll focus on the most interesting. In Si compounds (similar to carbon) 4-valentene.In air, silicon is stable even at elevated temperatures due to the formation of a protective oxide film. In oxygen it oxidizes starting at 400 °C, forming silicon oxide (IV) SiO2.
Silicon is resistant to acids and dissolves only in a mixture of nitric and hydrofluoric acids, and easily dissolves in hot alkali solutions with the release of hydrogen.
Silicon forms 2 groups of oxygen-containing silanes - siloxanes and siloxenes. Silicon reacts with nitrogen at temperatures above 1000 °C. Of great practical importance is the nitride Si3N4, which does not oxidize in air even at 1200 °C, is resistant to acids (except nitric) and alkalis, as well as to molten metals and slags, which makes it is a valuable material for the chemical industry, as well as for the production of refractories. Silicon compounds with carbon (silicon carbide SiC) and boron (SiB3, SiB6, SiB12) are characterized by high hardness, as well as thermal and chemical resistance.
Obtaining Silicon
I think this is the most interesting part, let’s take a closer look here.Depending on the purpose there are:
1. Electronic quality silicon(so-called “electronic silicon”) - the highest quality silicon with a silicon content of over 99.999% by weight, the electrical resistivity of electronic quality silicon can be in the range from approximately 0.001 to 150 Ohm cm, but the resistance value must be ensured exclusively a given impurity, i.e., the entry of other impurities into the crystal, even if they provide a given electrical resistivity, is, as a rule, unacceptable.
2. Solar grade silicon(so-called “solar silicon”) - silicon with a silicon content of over 99.99% by weight, used for the production of photovoltaic converters (solar batteries).
3. Technical silicon- silicon blocks of polycrystalline structure obtained by carbothermic reduction from pure quartz sand; contains 98% silicon, the main impurity is carbon, characterized by a high content of alloying elements - boron, phosphorus, aluminum; mainly used to produce polycrystalline silicon.
Technical purity silicon (95-98%) is obtained in an electric arc by reducing silica SiO2 between graphite electrodes. In connection with the development of semiconductor technology, methods have been developed for producing pure and highly pure silicon. This requires the preliminary synthesis of the purest initial silicon compounds, from which silicon is extracted by reduction or thermal decomposition.
Polycrystalline silicon (“polysilicon”) is the purest form of industrially produced silicon - a semi-finished product obtained by purifying technical silicon using chloride and fluoride methods and used for the production of mono- and multicrystalline silicon.
Traditionally, polycrystalline silicon is obtained from technical silicon by converting it into volatile silanes (monosilane, chlorosilanes, fluorosilanes) with subsequent separation of the resulting silanes, rectification purification of the selected silane and reduction of the silane to metallic silicon.
Pure semiconductor silicon is obtained in two forms: polycrystalline(reduction of SiCl4 or SiHCl3 with zinc or hydrogen, thermal decomposition of SiI4 and SiH4) and monocrystalline(crucible-free zone melting and “pulling” a single crystal from molten silicon - Czochralski method).
Here you can see the process of growing silicon using the Czochralski method.
Czochralski method- a method of growing crystals by pulling them upward from the free surface of a large volume of melt with the initiation of crystallization by bringing a seed crystal (or several crystals) of a given structure and crystallographic orientation into contact with the free surface of the melt.
Application of Silicon
Specially doped silicon is widely used as a material for the manufacture of semiconductor devices (transistors, thermistors, power rectifiers, thyristors; solar photocells used in spacecraft, as well as many other things).Since silicon is transparent to rays with wavelengths from 1 to 9 microns, it is used in infrared optics.
Silicon has diverse and expanding applications. In metallurgy Si
used to remove oxygen dissolved in molten metals (deoxidation).
Silicon is a component of a large number of alloys of iron and non-ferrous metals.
Typically, Silicon gives alloys increased resistance to corrosion, improves their casting properties and increases mechanical strength; however, at higher levels Silicon can cause brittleness.
The most important are iron, copper and aluminum alloys containing silicon.
Silica is processed by glass, cement, ceramics, electrical and other industries.
Ultra-pure silicon is primarily used for the production of single electronic devices (for example, your computer processor) and single-chip microcircuits.
Pure silicon, ultra-pure silicon waste, purified metallurgical silicon in the form of crystalline silicon are the main raw materials for solar energy.
Monocrystalline silicon - in addition to electronics and solar energy, is used to make gas laser mirrors.
Ultrapure silicon and its products
Silicon in the body
Silicon is found in the body in the form of various compounds, mainly involved in the formation of hard skeletal parts and tissues. Some marine plants (for example, diatoms) and animals (for example, siliceous sponges, radiolarians) can accumulate especially large amounts of silicon, forming thick deposits of silicon (IV) oxide when they die on the ocean floor. In cold seas and lakes, biogenic silts enriched with silicon predominate; in tropical seas, calcareous silts with a low silicon content predominate. Among terrestrial plants, cereals, sedges, palm trees, and horsetails accumulate a lot of silicon. In vertebrates, the content of silicon (IV) oxide in ash substances is 0.1-0.5%. Silicon is found in the largest quantities in dense connective tissue, kidneys, and pancreas. The daily human diet contains up to 1 g of silicon. When there is a high content of silicon (IV) oxide dust in the air, it enters the human lungs and causes the disease silicosis.Conclusion
Well, that's all, if you read to the end and delve a little deeper, then you are one step closer to success. I hope I didn’t write in vain and at least someone liked the post. Thank you for your attention.- Equisetaceae department general characteristics and significance What structure does a horsetail spore have?
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