Abstract: “Silicon, its properties and allotropic changes. Silicon is a biogenic element. Silicon, its properties and allotropic modifications - chemical features of silicon

Crystalline silicon is a dark gray material with a steel luster. The structure of silicon is similar to the structure of diamond: the crystal lattice is cubic face-centered, but due to the longer bond between the atoms Si-Si versus bond length C-C The hardness of silicon is much less than diamond. Silicon is very fragile, its density is 2.33 g / cm 3.

Like coal, refers to refractory substances.

The crystalline structure of silicon (Fig. 2).

The crystal lattice of silicon is a cubic face-centered type of diamond, the parameter a = 0.54307 nm (other polymorphic modifications of silicon are obtained at high pressures), but due to the longer bond length between the atoms Si-Si versus bond length C-C The hardness of silicon is much less than diamond. Silicon is fragile, only when heated above 800 ° C it becomes a plastic substance. Interestingly, silicon is transparent to infrared radiation, starting at a wavelength of 1.1 micrometers. Own carrier concentration - 13.1 × 10 28 m? 3

Figure 2. Silicon lattice and covalent chain bonding scheme: a - covalent bond; b - general view

Chemical properties

In compounds, silicon tends to exhibit an oxidation state of +4 or? 4, since the silicon atom is more characteristic of the sp 3 state — hybridization of orbitals. Therefore, in all compounds except silica (II) Sio, silicon is tetravalent.

Chemically silicon is inactive. At room temperature, it reacts only with gaseous fluorine, and volatile silicon tetrafluoride is formed. SiF 4 . When heated to a temperature of 400--500 ° C, silicon reacts with oxygen to form dioxide Sio 2 , with chlorine, bromine and iodine - with the formation of the corresponding easily volatile tetrahalides SiHalogen 4 .

Silicon does not directly react with hydrogen, silicon compounds with hydrogen are silanes with the general formula Si n H 2n + 2 - Obtained indirectly. Monosilane SiH 4 (it is often called simply silane) is released when metal silicides interact with acid solutions, for example:

Ca 2 Si + 4HCl\u003e 2CaCl 2 + SiH 4 ^

Silane formed in this reaction SiH 4 contains an admixture of other silanes, in particular, disilane Si 2 H 6 and trisilane Si 3 H 8 in which there is a chain of silicon atoms interconnected by single bonds (-Si-Si-Si-).

With nitrogen, silicon at a temperature of about 1000 ° C forms a nitride Si 3 N 4 , with boron - thermally and chemically resistant borides Sib 3 SiB 6 and sib 12 . The compound of silicon and its closest analogue on the periodic table - carbon - silicon carbide SiC (carborundum) is characterized by high hardness and low chemical activity. Carborundum is widely used as an abrasive.

When silicon is heated with metals, silicides occur. Silicides can be divided into two groups: ionic-covalent (alkali metal, alkaline earth metal silicides and magnesium Ca 2 Si, Mg 2 Si and others.) and metal-like (transition metal silicides). Silicides of active metals decompose under the action of acids, transition metal silicides are chemically stable and do not decompose under the action of acids. Metal-like silicides have high melting points (up to 2000 ° C). Metal-like silicides of compositions are most often formed. Mesi me 3 Si 2 Me 2 Si 3 Me 5 Si 3 and mesi 2 . Metal-like silicides are chemically inert, resistant to the action of oxygen even at high temperatures.

When restoring Sio 2 silicon at high temperatures forms silica (II) Sio.

Silicon is characterized by the formation of organosilicon compounds in which silicon atoms are connected in long chains by bridging oxygen atoms - ABOUT-, and to each atom of silicon, except for two atoms ABOUTadded two more organic radicals R 1 and R 2 = CH 3 , C 2 H 5 , C 6 H 5 CH 2 CH 2 CF 3 and etc.

For etching silicon, the most widely used is a mixture of hydrofluoric and nitric acids. Some special pickers provide for the addition of chromic anhydride and other substances. During etching, the acid etching solution is quickly heated to the boiling point, while the etching rate increases many times over.

Si + 2HNO 3 = SiO 2 + NO + NO 2 + H 2 O

Sio 2 + 4HF = SiF 4 + 2H 2 O

3SiF 4 + 3H 2 O = 2H 2 SiF 6 + vH 2 Sio 3

For the etching of silicon can be used aqueous solutions of alkalis. Etching of silicon in alkaline solutions begins at a solution temperature of more than 60 ° C.

Si + 2KOH + H 2 O = k 2 Sio 3 + 2H 2 ^

K 2 Sio 3 + 2H 2 O-h 2 Sio 3 + 2KOH

Physical properties

The crystal lattice of silicon cubic face-centered diamond type, parameter but = 0.54307 nm (other polymorphic modifications of silicon were obtained at high pressures), but due to the longer bond length between atoms Si-Si in comparison with the length of the C – C bond, the hardness of silicon is considerably less than that of diamond. Silicon is fragile, only when heated above 800 ° C it becomes a plastic substance. Interestingly, silicon is transparent to infrared radiation, starting at a wavelength of 1.1 micrometers. Own charge carrier concentration - 13.1 · 10 28 m? 3

Electrophysical properties

Elemental silicon in monocrystalline form is a non-direct-gap semiconductor. The band gap at room temperature is 1.12 eV, and at T = 0 K is 1.21 eV. The concentration of intrinsic charge carriers in silicon under normal conditions is about 1.5 · 10 10 cm? 3.

The electrophysical properties of crystalline silicon are greatly influenced by the impurities contained in it. To obtain silicon crystals with hole conductivity, atoms of elements of the third group, such as boron, aluminum, gallium, indium, are introduced into silicon). To obtain silicon crystals with electronic conductivity, atoms of the elements of the Vth group, such as phosphorus, arsenic, and antimony, are introduced into silicon. (pic. 3)

Figure 3. Silicon crystals and wafers for semiconductor manufacturing

When creating electronic devices based on silicon, the near-surface layer of the material is used (up to tens of microns), so the quality of the crystal surface can have a significant impact on the electrical properties of silicon and, accordingly, the properties of the finished device. When creating some devices, techniques are used related to surface modification, for example, by treating the surface of silicon with various chemical agents.

1. Dielectric permeability: 12

2. Electron mobility: 1300-1450 cmІ / (in · c).

3. Hole mobility: 500 cm² / (in · c).

4. The width of the forbidden zone of 1.205-2.84 · 10 -4 · T

5. Electron lifespan: 5 ns - 10 ms

6. The electron mean free path: about 0.1 cm

7. The length of the free run of the hole: about 0.02 - 0.06 cm

Municipal educational institution

"Secondary school № 6"

Cities of Murom

Abstract in Chemistry on the topic:

“Silicon, its properties and allotropic changes. Silicon - a biogenic element "

Fulfilled student 8 In class

Shvetsova Tatyana

Head Kornyshova S.S.

Introduction 3

Silicon Discovery History 4

Silicon in nature and its industrial mining 5

Silicon, its properties and allotropic modifications 7

Ways to get silicon 10

Silicon compounds and their properties 11

Silicon - Nutrient 14

Silicate industry 17

Conclusion 19

Literature 20

Introduction

The healing properties of silicon were known long before our days: in ancient India and China, the healing properties of young bamboo containing silicon were long used in Russia, and white clay was used in Russia to treat anemic children and frail old people from poisoning and heartburn, from skin diseases. Even in the pharmaceutical practice of ancient India and China, and later the folk medicine of many countries used decoctions, infusions and extracts of such silicon-containing plants as horsetail, nettle, mountaineer, bamboo and the famous ginseng. For more than 200 years, silicon has been used in classical homeopathy, it is very popular in modern cosmetology and is widely used in mesotherapy for skin revitalization (rejuvenation).

Objective: To study the properties of silicon and its natural compounds, to improve knowledge about the structure of atoms.

· Determine the structure of silicon, the value of silicon and its compounds and their practical application.

· Highlight the value of silicon as a nutrient

· Identify the main areas of the silicate industry

Silicon Discovery History

Silicon is an element of the main subgroup of the fourth group of the third period of the periodic table of chemical elements. I. Mendeleev, with atomic number 14. Denoted by the symbol Si (lat. Silicium).

Pure Creme was isolated in 1811 by French scientists Joseph Louis Gay-Lussac and Louis Jacques Tenard.

In 1825, the Swedish chemist Johns Jakob Berzelius, by the action of metallic potassium on silicon fluoride SiF 4, obtained pure elemental silicon. The new element was given the name "silicium" (from the Latin. Silex - flint). The Russian name "silicon" was introduced in 1834 by the Russian chemist German Ivanovich Hess. Translated from the ancient Greek.κρημνός - "cliff, mountain."

(from Latin. silicis - flint; Russian name from the Greek - kremnos - cliff) Si - discovered by J.
Berzelius (Stockholm, Sweden) in 1824. And here is silicon (Silicium - lat.) Chemical element, atomic number 14, group IV of the periodic system.

In 1825, the Swedish chemist Johns Jacob Berzelius, by the action of metallic potassium on silicon fluoride SiF 4, obtained pure elemental silicon. 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 the Greek kremnos - “cliff, mountain”.

Being in nature

Silicon in nature and its industrial mining

Most often in nature, silicon is found in the form of silica - compounds based on silicon dioxide (IV) SiO 2 (about 12% of the mass of the earth's crust). The main minerals formed by silicon dioxide are sand (river and quartz), quartz and quartzite, flint. The second most common group of silicon compounds in nature is silicates and aluminosilicates.

There are isolated facts of finding pure silicon in its native form: Metallic silicon in ijolitah of the Hot Mining massif, Petrology of ordinary chondrites.

· SiO 2 + 2Mg = 2MgO + Si,

Silicon, its properties and allotropic modifications

Crystalline silicon is a dark gray substance with a steel luster. The structure of silicon is similar to that of diamond: the crystal lattice is cubic face-centered, but because of the longer bond between Si-Si atoms compared to the C – C bond length, the hardness of silicon is much less than diamond. Silicon is very fragile, its density is 2.33 g / cm 3.

Like coal, refers to refractory substances.

Crystal structure of silicon.

Chemical properties

1. Si + 2HNO 3 = SiO 2 + NO + NO 2 + H 2 O

2. SiO 2 + 4HF = SiF 4 + 2H 2 O

3. 3SiF 4 + 3H 2 O = 2H 2 SiF 6 + ↓ H 2 SiO 3

1. Si + 2KOH + H 2 O = K 2 SiO 3 + 2H 2

2. K 2 SiO 3 + 2H 2 O↔H 2 SiO 3 + 2KOH

Physical properties

The crystal lattice of silicon is a cubic face-centered diamond type, parameter a = 0.54307 nm (other polymorphic modifications of silicon were obtained at high pressures), but due to the longer bond length between Si-Si atoms compared to the C – C bond length, the silicon hardness is significantly less than a diamond. Silicon is fragile, only when heated above 800 ° C it becomes a plastic substance. Interestingly, silicon is transparent to infrared radiation, starting at a wavelength of 1.1 micrometers. The intrinsic concentration of charge carriers is 13.1 × 10 28 m −3

Electrophysical properties

Elemental silicon in single-crystal form is an indirect band gap semiconductor. Band gap at room

temperature is 1.12 eV, and at T = 0 K is 1.21 eV. The concentration of intrinsic charge carriers in silicon under normal conditions is about 1.5 × 10 10 cm −3 [source not specified 342 days].

1. Dielectric permeability: 12

2. The mobility of electrons: 1300-1450 cm² / (in · c).

3. Hole mobility: 500 cm² / (in · c).

4. The width of the forbidden zone of 1,205-2,84 × 10 -4 · T

5. Electron lifespan: 5 ns - 10 ms

6. The electron mean free path: about 0.1 cm

7. The length of the free run of the hole: about 0.02 - 0.06 cm

Ways to get silicon

Free silicon can be obtained by calcining fine white sand with magnesium, which by chemical composition is almost pure silicon oxide,

· SiO 2 + 2Mg = 2MgO + Si,

the amorphous silicon formed in this case has the form of a brown powder, the density of which is 2.0 g / cm ³

In industry, technical grade silicon is obtained by reducing the SiO 2 melt with coke at about 1800 ° C in arc furnaces. The purity of the silicon thus obtained can reach 99.9% (the main impurities are carbon, metals).

Possible further purification of silicon from impurities.

· Cleaning under laboratory conditions can be carried out by preliminary preparation of magnesium silicide Mg 2 Si. Further, gaseous monosilane SiH 4 is obtained from magnesium silicide using hydrochloric or acetic acids. Monosilane is purified by distillation, sorption, and other methods, and then decomposed into silicon and hydrogen at a temperature of about 1000 ° C.

· Purification of silicon on an industrial scale is carried out by direct chlorination of silicon. Compounds of the composition SiCl 4 and SiCl 3 H are formed. These chlorides are purified from impurities in various ways (usually by distillation and disproportionation) and are reduced at the final stage with pure hydrogen at temperatures from 900 to 1100 ° C.

· Developing cheaper, cleaner, and more efficient industrial silicon purification technologies. For 2010, these include silicon purification technology using fluorine (instead of chlorine); technologies for the distillation of silicon monoxide; technologies based on the etching of impurities, concentrating on the intercrystalline boundaries.

The method of producing silicon in its pure form was developed by Nikolai Nikolayevich Beketov.

The largest producer of silicon in Russia is OKRusal - silicon is produced at plants in the city of Kamensk-Uralsky (Sverdlovsk region) and the city of Shelekhov (Irkutsk region).

Silicon compounds and their properties

Connections silicon

Silicon carbide (SiC) Silanes (Si n H 2n + 2) Fluorosilicic acid (H 2) Silicic acids (SiO 2 · n H 2 O) Silicon oxide (II) (SiO) Silicon oxide (IV) (SiO 2) Feldspar Silica gel ( n SiO2 · m H 2 O) Silicone oil Silicones (n) Vanadium silicide (V 3 Si) Rhenium silicide (ReSi) Molybdenum silicide (MoSi 2) Antimony silicate (Si 3 Sb 4) Bismuth silicide (Si 3 Bi 4) Polonium silicide (SiPo 2) Calcium silicide (CaSi 2) Manganese silicide (Mg 2 Si) Trichlorosilane (SiHCl 3) Silicon Chloride (IV) (SiCl 4) Silicon Chlorides Silicon Nitride (Si 3 N 4) Silicon Tetraiodide (SiI 4) Silicon Tetrabromide (SiBr 4) Sulfide silicon (SiS 2) Moissanite

By chemical properties, silicon is a non-metal. Since at the external energy level there are 4 electrons, the degree of oxidation of both -4 and +4 is characteristic of silicon. Chemically, silicon is little active. At room temperature, it only reacts with fluorine gas, and volatile silicon tetrafluoride is formed:

Si + 2F 2 = SiF 4

When heated, crushed silicon reacts with oxygen to form silicon oxide (IV):

Si + O 2 = SiO 2

Acids (except the mixture of hydrogen fluoride and nitrogen) do not affect silicon. However, it dissolves in alkalis, forming silicate and hydrogen.

Si + 2 NaOH + H 2 O = Na 2 SiO 3 + 2H 2

In compounds, silicon tends to exhibit a degree of oxidation of +4 or −4, since the state of sp 3 hybridization of orbitals is more characteristic of the silicon atom. Therefore, in all compounds except silicon oxide (II) SiO, silicon is tetravalent.

Chemically, silicon is inactive. At room temperature it reacts only with gaseous fluorine, and volatile silicon tetrafluoride SiF 4 is formed. When heated to a temperature of 400-500 ° C, silicon reacts with oxygen to form SiO 2 dioxide, with chlorine, bromine and iodine to form the corresponding easily volatile tetrahalides of SiHalogen 4.

Silicon does not directly react with hydrogen, silicon compounds with hydrogen — silanes with the general formula Si n H 2n + 2 — are obtained indirectly. Monosilane SiH 4 (it is often called simply silane) is released when metal silicides interact with acid solutions, for example:

Ca 2 Si + 4HCl → 2CaCl 2 + SiH 4.

The silane SiH 4 formed in this reaction contains an admixture of other silanes, in particular, disilane Si 2 H 6 and trisilane Si 3 H 8, in which there is a chain of silicon atoms linked by single bonds (-Si-Si-Si-) .

With nitrogen, silicon at a temperature of about 1000 ° C forms a nitride of Si 3 N 4, with boron — thermally and chemically resistant borides SiB 3, SiB 6 and SiB 12. The compound of silicon and its closest analogue on the periodic table - carbon - silicon carbide SiC (carborundum) is characterized by high hardness and low chemical activity. Carborundum is widely used as an abrasive.

When silicon is heated with metals, silicides occur. Silicides can be divided into two groups: ionic-covalent (alkali metal, alkaline earth metal silicides and type Ca 2 Si, Mg 2 Si, etc.) and metal-like (transition metal silicides). Silicides of active metals decompose under the action of acids, transition metal silicides are chemically stable and do not decompose under the action of acids. Metal-like silicides have high melting points (up to 2000 ° C). Metal-like silicides of the compositions MeSi, Me 3 Si 2, Me 2 Si 3, Me 5 Si 3 and MeSi 2 are most often formed. Metal-like silicides are chemically inert, resistant to the action of oxygen even at high temperatures.

When SiO 2 is reduced by silicon at high temperatures, silicon oxide (II) SiO is formed.

Silicon is characterized by the formation of organosilicon compounds in which silicon atoms are joined in long chains by the bridging oxygen atoms —O-, and to each silicon atom, except for two O atoms, two more organic radicals R 1 and R 2 = CH 3, C are attached 2 H 5, C 6 H 5, CH 2 CH 2 CF 3, etc.

4. Si + 2HNO 3 = SiO 2 + NO + NO 2 + H 2 O

5. SiO 2 + 4HF = SiF 4 + 2H 2 O

6. 3SiF 4 + 3H 2 O = 2H 2 SiF 6 + ↓ H 2 SiO 3

For the etching of silicon can be used aqueous solutions of alkalis. Etching of silicon in alkaline solutions begins at a solution temperature of more than 60 ° C.

3. Si + 2KOH + H 2 O = K 2 SiO 3 + 2H 2

4. K 2 SiO 3 + 2H 2 O↔H 2 SiO 3 + 2KOH

it is a material about the most resistant natural compound of silicon - silicon oxide (IV). These are silica, quartz, transparent quartz crystals - rock crystal, a fine-crystalline variety of quartz - jasper, fine quartz grains - sand (all samples are presented at the exhibition and are demonstrated). Silicates are also extremely common in nature.

For example:

Kaolinite is the main component of white clay.

Of artificial silicates ceramics, glass and cement are of the greatest importance. Let's get acquainted with the production of some of the materials produced by the silicate industry, more.

Silicon - Nutrient

In the human body, the silicon content is 7-10 years, it is found in the blood, in the muscles, in the immune competent organs - the thymus gland and the adrenal glands. Silicon is the main structural element in the human body, if calcium is an element of rigid bone structures of the musculoskeletal system, then silicon is an element of flexible structures, it is necessary for the formation and development of connective tissue, which is widely represented in our body - bones, joints, cartilage, tendons, lens of the eye, blood vessels, as well as skin, mucous membranes, hair and nails. Connective tissue has a property that distinguishes it from other tissues of the body - the ability to regenerate (restore). The high content of silicon in the connective tissue is due to its presence in the composition of protein complexes that form the skeleton of tissues and give them strength and elasticity. Silicon is involved in chemical reactions that hold individual fibers of collagen and elastin, prevents the formation of wrinkles, normalizes skin hydration, strengthens hair and nails. Silicon compounds are essential activators of the regeneration of connective tissue in the human body, they accelerate metabolic processes in the body, have a stimulating effect on the growth of skin cells, the production of collagen, elastin and keratin. The ability of silicon to structure water and body fluids is known, it reduces the surface tension of water, making it more bioavailable, thus silicon promotes hydration of cells and tissues. It has been revealed that in children the saturation of body tissues with fluid is higher than that of older people, therefore silicon plays a significant role in preventing the aging process of the body. Being a structural antioxidant, silicon blocks lipid peroxidation processes, which has a positive effect on enhancing the protective function of the skin and increasing the resistance of hair and nails to the oxidative action of free radicals. Since the biological age of a person is determined precisely by the rate of metabolic processes, the lack of silicon in the body is one of the causes of aging.

Scientific studies have shown that silicon is involved in the metabolism of more than 70 trace elements (calcium, magnesium, fluorine, sodium, sulfur, aluminum, zinc, molybdenum, manganese, cobalt, and many others); they are not absorbed if the body lacks silicon. The lack of silicon in the body entails microelementoses, disorders of the functions of many body systems and metabolic disorders. Violation of silicon metabolism leads to anemia, osteoporosis, hair loss, diseases of the joints, tuberculosis, diabetes, erysipelas of the skin, gallstone and urolithiasis

The unique ability of silicon to purify living organisms has long been known, its organic compounds can form in the aquatic environment of the body bioelectrically charged systems that “stick” viruses of influenza, hepatitis, herpes, pathogens, fungi and deactivate them to themselves. It is known that silicon deficiency is always accompanied by dysbacteriosis, the most frequent manifestation of which is candidiasis, manifested as ulcerative lesions of the oral mucosa, nose, upper respiratory tract, digestive tract and urinary system. Silicon colloids form complex compounds with Candides and their toxins and remove them from the body. Normal flora of the intestine, which includes bifidobacteria and lactobacilli, does not have the ability to connect with colloidal silicon systems and remains in the intestine, which is very important for normal functioning

digestive tract. Not to mention the value of silicon for the immune system: blood cells that are responsible for the protective functions of the body (monocytes, lymphocytes) and produce protective antibodies - are representatives of the connective tissue. That is why silicon deficiency reduces immunity and various diseases appear that are protracted, most often these are purulent processes - furunculosis, abscesses, sinusitis, otitis, tonsillitis, nonhealing wounds and fistulas. It has already been proven that many serious diseases (cancer, tuberculosis, leprosy, cataracts, hepatitis, dysentery, rheumatism, arthritis) are associated either with a lack of silicon in the tissues, or with a violation of its metabolism. Silicon has anti-inflammatory and immunostimulating effect in respiratory infections and chronic bronchitis, reduces allergic reactions in bronchial asthma. Scientists have long paid attention to the fact that in areas where the soil is rich in silicon, cancer is extremely rare.

We get silicon with water, plant and animal food, the daily need for silicon is 20-30 mg, especially pregnant women, nursing mothers and children need silicon especially. Organs and systems are actively formed in the children's organism and the need for a binding element is much higher than that of an adult. With silicon deficiency in children’s bodies, rickets develops, teeth are destroyed and caries progresses, children lag behind in physical and intellectual development. In adults, caries joins hair loss, fragility and brittle nails. With age, the ingestion of silicon decreases, calcium takes its place in the bones, so the bones lose elasticity, harden, become brittle, and osteoporosis occurs. In approximately the same way, osteochondrosis develops in the body: intervertebral cartilages are filled with calcium, lose their elasticity, become thinner, and their mobility deteriorates. When reducing the amount of silicon in the body, calcium is not absorbed by the bone tissue, in the form of salts it is deposited in the joints, and in the form of sand and stones - in the gall bladder and kidneys, causing the occurrence of gouty syndrome. In the process of aging, the risk of fractures increases significantly, it is proved that a powerful accumulation of silicon occurs in the place of a fracture and its quantity increases 50 times in comparison with healthy parts of the bone. The body sends it to the problem area "to help" for the speedy formation of new bone tissue. Enrollment of silicon promotes calcium fixation in bones, improves elasticity and muscle tone, strengthens the ligaments and cartilage of the joints. It is known that the age of a person can be judged by the state of his blood vessels. In 1957, French scientists described the facts confirming that atherosclerosis there is a very low silicon content in the walls of blood vessels. With silicon deficiency, calcium replaces it, therefore, the elasticity of blood vessels decreases and at the same time the permeability of their walls increases, cholesterol enters the blood through the formed defects from tissues and settles on the walls of blood vessels, forming cholesterol plaques. This process leads to vasoconstriction and causes angina, heart attack, arrhythmia, stroke, hypertension, mental disorders, memory impairment, etc. With a silicon deficiency, elasticity and venous vessels suffer, veins stretch and change their position, and a varicose disease of the lower extremities appears. A sufficient amount of silicon in the daily diet can restore the inner lining of blood vessels, restore elasticity to them, improve the venous circulation and help reduce low-density cholesterol. Silicon is a universal and absolutely safe stimulator of energy production in the body when it enters the body's cells.

there is an active synthesis of adenosine triphosphate (ATP) - a molecule that provides energy for all biochemical processes occurring in cells.

Biological role

For some organisms, silicon is an important nutrient. It is part of the support formations in plants and skeletal - in animals. Silicon is concentrated in large quantities by marine organisms - diatoms, radiolarians, sponges. Large quantities of silicon concentrate horsetails and cereals, first of all - the subfamily Bamboks and Risovidnyh, including - sowing rice. Human muscle tissue contains (1-2) × 10 −2% silicon, bone tissue - 17 × 10 −4%, blood - 3.9 mg / l. Every day up to 1 g of silicon enters the human body with food.

Silicon compounds are relatively non-toxic. But it is very dangerous to inhale highly dispersed particles of both silicates and silicon dioxide, which are formed, for example, by blasting, by chiseling rocks in mines, by sandblasting devices, etc. SiO 2 microparticles that fall into the lungs crystallize in them, and the resulting crystals destroy the lung tissue and cause severe disease - silicosis. To prevent dangerous dust from entering the lungs, a respirator should be used to protect respiratory organs.

Silicate industry

Gzhel is one of the traditional Russian centers for the production of ceramics. This is a vast area consisting of 27 villages united in the “Gzhelsky Bush” located about 60 kilometers from Moscow along the Moscow-Murom-Kazan railway line. Now this is the Ramensky District of the Moscow Region (shown on the map of the Moscow Region).

Gzhel has long been famous for its clay. The great Russian scientist M. V. Lomonosov, who appreciated the Gzhelian clay, wrote such lofty words about them: “There is hardly a purest earth and without any use wherever the world chemists call us Gzhel, which I have never seen more beautifully nowhere” . Up to the middle of the XVIII century, Gzhel made pottery, usual for that time, made bricks, pottery pipes, as well as primitive children's toys.

The second half of the XVIII century - semi-faience, obtained as an intermediate material in search of the porcelain recipe, painted with blue smalt on a gray, thick, porous shard. The painting on kvasniki, jugs, plates wore a graphic character and looked like a painted outline drawing.

The beginning of the XIX century - the era of porcelain. The porcelain of private factories in Gzhel was distinguished by great brightness, a combination of contrasting paints of various forms of everyday objects.

In 1972, the modern Gzhel product style was created using cobalt blue paint.

The slender artistic system of Gzhel writing was consolidated in individual handwritings and peculiar manners of the performers. Using the same set of pictorial elements in his work, each artist created his own individual painting story: a bouquet or a separate flower, animal or plant world, images of people.

An important feature in the Gzhel blue-and-white porcelain painting is a picturesque beginning. Great importance is attached to the movement of the brush, capable of creating a multitude of subtlest gradations of blue color: from sonorous saturated to blurred blue. In combination with a white background, the picture creates an openwork pattern on the surface of the product: in the center - a bright, large spot - an image of a flower, and around a light scattering of twigs with leaves and berries, curls, tendrils.

Porcelain painter paints painted with cobalt (II) oxide.

Now it is impossible to say exactly who and when invented glass. It is only known that glass is one of the oldest inventions of mankind. Thus, the necklace found on the mummy's neck of the Egyptian queen Hatshepsut, consisting of greenish-black glass beads, is 3,400 years old. The great masters of the production of various glass products were Roman glassmakers. They made jugs for water, oil and wine, cups and cups, vases, teardrops - tiny perfume bottles. A major contribution to the development of art glassmaking in Russia was made by Lomonosov. In created by him in 1748

about 4000 experiments on color glass boiling were carried out by the chemical laboratory, for which Lomonosov “not only wrote recipes, but also materials ... he mostly hung them up and put them in the oven ...” On the basis of the recipes developed by Lomonosov, a glass factory in Ust– Ruditsa in 1753 began to produce multi-colored transparent glass for the manufacture of beads, dishes and other haberdashery and opaque to mosaic. From such glass, Lomonosov made several mosaic paintings, among which was the “Poltava Battle”, which received the greatest fame and has survived to the present day.

The composition of ordinary window glass is expressed by the formula Na 2 O * CaO * 6SiO 2

We use quartz sand, soda and limestone to produce ordinary glass. These substances are thoroughly mixed and subjected to strong heating. The chemistry of the process can be represented as follows: during fusion, silicates of sodium and calcium are formed, which then fuse with silica (in excess):

SiO 2 + Na 2 CO 3 = Na 2 SiO 3 + CO 2

SiO 2 + CaCO 3 = CaSiO 3 + CO 2

Na 2 SiO 3 + CaSiO 3 + 4SiO 2 = Na 2 O * CaO * 6SiO 2

For special glass change the composition of the initial mixture. Replacing soda with Na 2 CO 3 potash K 2 CO 3, get refractory glass (for chemical glassware). Replacing chalk CaCO 3 lead oxide (II) PbO, and potash soda, get crystal glass. It is rather soft and fusible, but very heavy, it is distinguished by strong brilliance and high coefficient of light refraction, decomposing light rays into all colors of the rainbow and causing the play of light.

The inclusion of boron oxide instead of alkaline constituents gives this glass refractory properties.

Ordinary glass mass after cooling has a yellowish-green or bluish-green shade. Glass can be colored if the composition of the mixture to make the inclusion of certain metal oxides. Ferrous compounds paint glass in colors - from bluish-green and yellow to red-brown, manganese (IV) oxide - from yellow and brown to purple, chromium (III) oxide in grass-green, cobalt (II) oxide - in blue, Nickel (II) oxide - from violet to gray-brown, sodium sulfide - to yellow, copper (II) oxide - to red.

In human life, glass has gained tremendous importance. It is visible everywhere, it is at every step - in the everyday life of our life, in industry, in technology, in science, in works of art. Window, bottle, lamp, mirror, glass of home and laboratory glassware, optical glass (from glasses glasses to complex anastigmats of cameras), lenses of endless optical devices - from microscopes to telescopes. It is difficult to list all the applications of glass and it is impossible to count the various objects made from it. This material, due to its unique properties, pleases and, probably, is charming, will always be present in life capable of appreciating its beauty.

Conclusion

So, today it is proved that silicon contributes to:

· Cleansing and strengthening the body and efficient absorption of nutrients, macro- and microelements

· Increase the overall tone, increase the body's energy resources, improve mental performance, slow the aging process

· Elimination of disorders caused by the harmful effects of free radicals, preventing the development of many chronic diseases

Silicon atoms form the basis of clay, sand and rocks. Most of the crust consists of inorganic silicon compounds (28 vol.%). We can say that the entire inorganic world is associated with silicon. Under natural conditions, silicon minerals are also found in calcites and chalk. Silicon is the second element after oxygen in terms of reserves in the crust and makes up about one third of its total weight. Every 6 atom in the earth’s crust is a silicon atom. Silicon in sea water contains even more than phosphorus, which is so necessary for life on Earth. In our body, silicon is found in the thyroid gland, adrenal glands, pituitary gland. Its highest concentration is found in hair and nails. Silicon is also a component of collagen, the main protein of connective tissue. Its main role is participation in a chemical reaction, fastening individual fibers of collagen and elastin, giving the connective tissue strength and elasticity. The lack of silicon in the body leads to: osteomalacia (softening of the bones), diseases of the eyes, teeth, nails, skin and hair; accelerated wear of articular cartilage; erysipelas of the skin; stones in the liver and kidneys; dysbacteriosis; atherosclerosis. The relationship between the concentration of silicon in drinking water and cardiovascular diseases was found. Tuberculosis, diabetes, leprosy, hepatitis, hypertension, cataracts, arthritis, cancer are accompanied by a decrease in the concentration of silicon in the tissues and organs, or disorders of its metabolism. Meanwhile, our body loses silicon daily - on average, we consume 3.5 mg of silicon per day with food and water, and we lose about 9 mg per day.

Literature

· Samsonov. GV Silicides and their use in engineering. Kiev, Publishing House of the Academy of Sciences of the Ukrainian SSR, 1959. 204 pp. With ill.

· Aleshin E. P., Aleshin N. E. Fig. Moscow, 1993. 504 p. 100 fig.

"Carbon and silicon" - Well-ground diamond - a diamond. Soft graphite has a layered structure. Silicon oxide (IV). The specular carbon has a layered structure. Chemical properties. Carbon. Graphite. Methods of obtaining: laboratory and industrial. Glass. One of the softest among solids. More than 99% of carbon in the atmosphere is in the form of carbon dioxide.

"Silicon" - Interaction with metals. General characteristics of silicon on the position in the periodic system. Application. Products of silicate industry. Silicates - salts of silicic acid. Silicides In laboratories, silicon is produced by reducing silicon oxide SiO2. The structure of the silicon atom. Up to the end of the outer level, silicon lacks 4 electrons.

"Silicon Lesson" - On the manifestation of non-metallic and metallic properties. Choose the correct statements: Oxides, carbon and silicon hydroxides? The nature of the oxide: a) basic, b) acidic, c) amphoteric. Types of bond and crystal lattices in simple substances. Silicate industry. Express survey. Flower - five flowers.

"Silicon Compounds" - Cubic face-centered lattice. Jasper. Minerals based on SiO2. Agate. Silicon and its compounds. Silicates and hydrogen. Amethyst. Getting silicates. Getting silicon in the laboratory. The use of silicon. Chemical properties of SiO2. Natural silicates. Varieties of quartz. The discovery of silicon. Silicon oxide.

"Silicon isotopes" - Production of monocrystalline seed. The distribution of the concentration of isotopes along the length of the seed. Prospects for the use of monoisotopic silicon. Thermal conductivity of isotopically enriched silicon-28. Raman spectra of isotopically enriched silicon. Crucible. Dependence of the band gap of silicon on atomic mass.

"Silicon and its compounds" - Silicon can be both an oxidizing agent and a reducing agent. The crystal lattice of silicon resembles the structure of a diamond. Silicates Silicates account for more than 1/4 of the mass of the entire crust. Ceramics. Silicon was first discovered in 1811 by Gay-Lussac and Tenar. Modern pottery dishes. Consider natural silicon compounds.

There are 6 presentations in total.

Municipal educational institution

"Secondary school № 6"

Cities of Murom

Abstract in Chemistry on the topic:

“Silicon, its properties and allotropic changes. Silicon - a biogenic element "

Fulfilled student 8 In class

Shvetsova Tatyana

Head Kornyshova S.S.

Introduction 3

Silicon Discovery History 4

Silicon in nature and its industrial mining 5

Silicon, its properties and allotropic modifications 7

Ways to get silicon 10

Silicon compounds and their properties 11

Silicon - Nutrient 14

Silicate industry 17

Conclusion 19

Literature 20

Introduction

Objective: To study the properties of silicon and its natural compounds, to improve knowledge about the structure of atoms.

· Determine the structure of silicon, the value of silicon and its compounds and their practical application.

· Highlight the value of silicon as a nutrient

· Identify the main areas of the silicate industry

Silicon Discovery History

Pure Creme was isolated in 1811 by French scientists Joseph Louis Gay-Lussac and Louis Jacques Tenard.

Being in nature

Silicon in nature and its industrial mining

There are isolated facts of finding pure silicon in its native form: Metallic silicon in ijolitah of the Hot Mining massif, Petrology of ordinary chondrites.

· SiO 2 + 2Mg = 2MgO + Si,

Silicon, its properties and allotropic modifications

Like coal, refers to refractory substances.

Crystal structure of silicon.

Chemical properties

1. Si + 2HNO 3 = SiO 2 + NO + NO 2 + H 2 O

2. SiO 2 + 4HF = SiF 4 + 2H 2 O

3. 3SiF 4 + 3H 2 O = 2H 2 SiF 6 + ↓ H 2 SiO 3

1. Si + 2KOH + H 2 O = K 2 SiO 3 + 2H 2

2. K 2 SiO 3 + 2H 2 O↔H 2 SiO 3 + 2KOH

Physical properties

Electrophysical properties

Elemental silicon in single-crystal form is an indirect band gap semiconductor. Band gap at room

temperature is 1.12 eV, and at T = 0 K is 1.21 eV. The concentration of intrinsic charge carriers in silicon under normal conditions is about 1.5 × 10 10 cm −3 [source not specified 342 days].

1. Dielectric permeability: 12

2. The mobility of electrons: 1300-1450 cm² / (in · c).

3. Hole mobility: 500 cm² / (in · c).

4. The width of the forbidden zone of 1,205-2,84 × 10 -4 · T

5. Electron lifespan: 5 ns - 10 ms

6. The electron mean free path: about 0.1 cm

7. The length of the free run of the hole: about 0.02 - 0.06 cm

Ways to get silicon

Free silicon can be obtained by calcining fine white sand with magnesium, which by chemical composition is almost pure silicon oxide,

· SiO 2 + 2Mg = 2MgO + Si,

the amorphous silicon formed in this case has the form of a brown powder, the density of which is 2.0 g / cm ³

Possible further purification of silicon from impurities.

The method of producing silicon in its pure form was developed by Nikolai Nikolayevich Beketov.

The largest producer of silicon in Russia is OKRusal - silicon is produced at plants in the city of Kamensk-Uralsky (Sverdlovsk region) and the city of Shelekhov (Irkutsk region).

Silicon compounds and their properties

Connections silicon

Si + 2F 2 = SiF 4

When heated, crushed silicon reacts with oxygen to form silicon oxide (IV):

Si + O 2 = SiO 2

Acids (except the mixture of hydrogen fluoride and nitrogen) do not affect silicon. However, it dissolves in alkalis, forming silicate and hydrogen.

Si + 2 NaOH + H 2 O = Na 2 SiO 3 + 2H 2

Ca 2 Si + 4HCl → 2CaCl 2 + SiH 4.

When SiO 2 is reduced by silicon at high temperatures, silicon oxide (II) SiO is formed.

4. Si + 2HNO 3 = SiO 2 + NO + NO 2 + H 2 O

5. SiO 2 + 4HF = SiF 4 + 2H 2 O

6. 3SiF 4 + 3H 2 O = 2H 2 SiF 6 + ↓ H 2 SiO 3

For the etching of silicon can be used aqueous solutions of alkalis. Etching of silicon in alkaline solutions begins at a solution temperature of more than 60 ° C.

3. Si + 2KOH + H 2 O = K 2 SiO 3 + 2H 2

4. K 2 SiO 3 + 2H 2 O↔H 2 SiO 3 + 2KOH

For example:

Kaolinite is the main component of white clay.

Of artificial silicates ceramics, glass and cement are of the greatest importance. Let's get acquainted with the production of some of the materials produced by the silicate industry, more.

Silicon - Nutrient

there is an active synthesis of adenosine triphosphate (ATP) - a molecule that provides energy for all biochemical processes occurring in cells.

Biological role

Silicate industry

In 1972, the modern Gzhel product style was created using cobalt blue paint.

Porcelain painter paints painted with cobalt (II) oxide.

The composition of ordinary window glass is expressed by the formula Na 2 O * CaO * 6SiO 2

SiO 2 + Na 2 CO 3 = Na 2 SiO 3 + CO 2

SiO 2 + CaCO 3 = CaSiO 3 + CO 2

Na 2 SiO 3 + CaSiO 3 + 4SiO 2 = Na 2 O * CaO * 6SiO 2

The inclusion of boron oxide instead of alkaline constituents gives this glass refractory properties.

Conclusion

So, today it is proved that silicon contributes to:

· Cleansing and strengthening the body and efficient absorption of nutrients, macro- and microelements

· Increase the overall tone, increase the body's energy resources, improve mental performance, slow the aging process

· Elimination of disorders caused by the harmful effects of free radicals, preventing the development of many chronic diseases

Literature

· Samsonov. GV Silicides and their use in engineering. Kiev, Publishing House of the Academy of Sciences of the Ukrainian SSR, 1959. 204 pp. With ill.

· Aleshin E. P., Aleshin N. E. Fig. Moscow, 1993. 504 p. 100 fig.

Allotropy (from ancient Greek. Αλλος - “other”, τροπος - “turn, property”) - the existence of two or more simple substances of the same chemical element, different in structure and properties - the so-called allotropic modifications or forms.

The phenomenon of allotropy is due either to the different composition of the molecules of a simple substance (allotropy of the composition) or to the method of placing atoms or molecules in the crystal lattice (allotropy of form).

2.1 Crystal Silicon

Crystalline silicon is the main form in which silicon is used in the production of photoelectric converters and solid-state electronic devices using planar technology. The use of silicon in the form of thin films (epitaxial layers) of a crystalline and amorphous structure on various substrates is actively developing. Dark gray substance with metallic luster, great hardness, brittleness, semiconductor, inert.

Depending on the purpose, there are:

1 Silicon of electronic quality (the so-called "electronic silicon") - the highest quality silicon with a silicon content of more than 99.999% by weight, higher rates of lifetime (over 25 μs), used for the production of solid-state electronic devices, microcircuits, etc. The electrical resistivity of silicon of electronic quality can be in the range from about 0.001 to 150 Ohm · cm, but the resistance should be provided solely by the impurity, i.e. other impurities get into the crystal, although s and providing the specified electrical resistivity, as a rule, is unacceptable. The bulk of silicon crystals of electronic quality is the so-called. “dislocation-free crystals”, i.e., the dislocation density in them does not exceed 10 cm – 2, however, in some cases, for the manufacture of electronic devices, ingots with a twin or even polycrystalline structure are also used.

2 Solar grade silicon (the so-called “solar silicon”) is silicon with a silicon content of more than 99.99% by weight, with average values of the nonequilibrium carrier lifetimes and electrical resistivity (up to 25 μs and up to 10 Ω cm) used for production of photovoltaic cells (solar cells);

3 Technical silicon - blocks of silicon of polycrystalline structure, obtained by the method of carbothermic reduction from pure quartz sand; contains 98% of silicon, the main impurity is carbon, it has a high content of alloying elements - boron, phosphorus, aluminum; mainly used to produce polycrystalline

silicon; in 2006–2009 Due to the lack of solar-grade silicon raw materials, attempts were made to use this material for the production of crystalline silicon of solar quality: for this purpose, additional purification of technical silicon was performed by crushing at intercrystalline boundaries and etching impurities concentrating on the boundaries, then recrystallization was performed by one of the above methods).

Depending on the method of recrystallization, there are:

- monocrystalline silicon - cylindrical silicon ingots of mono- and polycrystalline structure with a diameter of up to 400 mm, obtained by the Czochralski method. In monosilicon, the crystal structure is uniform, without grain boundaries (which is noticeable even in appearance). The orderly arrangement of silicon atoms in a single crystal lattice of silicon creates a clear band structure. Each silicon atom has 4 electrons on the outer shell. The electrons of neighboring atoms form pairs that belong to both atoms at the same time, so each atom has 4 bonds with neighboring atoms.

The behavior of monocrystalline silicon is well predictable, however, due to the low growth rate and complexity of the manufacturing process, it is the most expensive type of silicon. Monocrystalline silicon is the basis of modern electronic technology. Extremely high demands on the purity and perfection of the structure are made to it. Concentrations of electrically active dopants are usually within 10 13 –10 18 cm ³, electrically active background impurities are less than 10 15 cm ³, and electrically inactive impurities are less than 10 18 –10 19 cm ³. The main types of structural defects are the so-called microdefects. As a rule, they are small dislocation loops or clusters of intrinsic and impurity point defects.

- silicon single-crystal non-crucible - cylindrical silicon ingots of single-crystal structure with a diameter up to 150 mm, obtained by the method of crucible-free zone melting;

- multisilicon - rectangular blocks of silicon of polycrystalline structure with dimensions up to 1000x1000x600mm, obtained by the method of directional crystallization in a container. It occupies an intermediate position between poly- and monocrystalline silicon in size and number of crystals. It is much easier to grow silicon multi-crystals than single crystals, so their cost is lower. However, the quality of the multicrystal as compared with a single crystal is also lower due to the presence of multiple grain boundaries of the single crystals of which the multicrystal is composed. The grain boundaries create additional defective levels in the band gap of the semiconductor, being local centers with a high recombination rate, which leads to a decrease in the total

lifetime of minority carriers. In addition, grain boundaries reduce performance by preventing carrier current and creating shunting paths for the current flowing through the p-n junction.

To avoid too large recombination losses at grain boundaries, the grain size should be at least several millimeters. This condition also means that the size of a single grain will be larger than the thickness of the solar cell, which will reduce the resistance to carrier current and the total length of the boundary regions in the solar cell. Such multicrystalline silicon is widely used in commercial solar cells.

- polysilicon is a high-purity silicon with an impurity content of less than 0.0001%, consisting of a large number of small crystal grains oriented randomly relative to each other.

In fact, technical silicon is also polycrystalline, however, to avoid confusion, the concept of "polycrystalline silicon" is applied only to highly pure semiconductor silicon. Polysilicon is the purest form of industrially produced silicon and the main material for microelectronics and solar energy - a semi-finished product obtained by purifying technical silicon with chloride methods and used for the production of mono- and multicrystalline silicon.

Currently, polysilicon "electronic" (semiconductor) quality (impurity content less than 1 · 10 -10%) and polysilicon "solar" quality (impurity content less than 1 · 10 -5%) are distinguished. Most polycrystalline silicon in the world is produced in the form cylindrical rods of gray color with a rough dendritic surface. In the center of the rod there is a “seed” of mono-or polysilicon of round or square section with a diameter (side) of 8–10 mm. Close-packed crystallites in the form of short needles, with a cross section of less than 1 mm, grow from the “seed” perpendicular to the generatrix.

Polysilicon is a raw material for the production of more advanced types of silicon - multicrystalline silicon (multisilicon) and monocrystalline silicon (monosilicon), and also in some applications it can be used in its pure form.

-. Silicon scrap - cuttings, fragments and other pure waste products of silicon production by methods described above without oxidation, fused parts of the crucible or lining - in turn, can be divided into subgroups depending on the origin - is used as working material in the production of crystalline silicon;

-. umg-scrap — metallurgically purified technical silicon — is technical silicon subjected to purification by interaction of the silicon melt with other substances (for extracting impurities or transferring them to an insoluble or gaseous phase, etc.) and after

following directional crystallization and subsequent removal of the zone of concentration of contaminants;

-. rot scrap - fragments, cuttings and other wastes of crystalline silicon production by methods described above with crucible or lining residues, traces of oxidation, slag — as a rule, this is also the area where impurities — most dirty silicon — were pushed back during crystallization — in turn, can be separated on subgroups, depending on their origin - after purification from impurities of foreign substances can be used as an additive to recyclable raw materials upon receipt of silicon grades with reduced quality requirements.

Silicon monocrystalline crucible is produced only electronic quality. Multi-silicon is produced only solar quality. Monocrystalline silicon, tubes and tapes obtained by the Czochralski method can be both electronic and solar quality.