Silicon is a chemical element, its chemical symbol is Si, the old name is Silicon. The atomic number is 14, and the relative atomic mass is 28.0855. Silicon Uses
There are two allotropes of Amorphous Silicon and Crystalline Silicon, belonging to the third period of the Periodic Table, the metal elements of the IVA group. Silicon is also an extremely common element.
However, it rarely appears in nature as a simple substance, but in the form of complex silicate or silica, which is widely found in rocks, gravel, and dust.
The reserves of silicon in the universe rank eighth. In the earth’s crust, it is the second most abundant element, constituting 26.4% of the total mass of the earth’s crust, second only to the first oxygen (49.4%).
Where is Silicon Found
The abundance of silicon has caused interest among early chemists. The content of germanium (silicon) on the surface of the earth is second only to Oxygen, accounting for nearly 28%.
But the germanium (silicon) element is not the first element discovered, because it is necessary to reduce the germanium from the oxide of germanium (silicon). A very difficult thing.
Silicon accounts for about 25.7% of the total weight of the earth’s crust, second only to oxygen.
In nature, silicon is usually present in the form of oxygenates, the simplest of which is the silicon and oxygen compound silica SiO2. Quartz, crystal, etc. are variants of pure silica.
Silicon oxides in ores and rocks are collectively referred to as silicates, and more important are Feldspar KAlSi3O8, Kaolin Al2Si2O5(OH)4, Talc Mg3(Si4O10)(OH)2, Mica KAl2(AlSi3O10 )(OH)2, Asbestos H4 Mg3Si2O9, Sodium Zeolite Na2(Al2Si3O10)2H2O, Garnet Ca3Al2(SiO4)3, Zirconium Quartz ZrSiO4 and Beryl Be3Al2Si6O18, Soil, Clay, and Sand are products of weathering of Natural Silicate Rocks.
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Silicon is widely distributed in nature, with an atomic percentage of 16.7% in the earth’s crust. It is a basic element of rock minerals, appearing as quartz sand and silicate.
The content of silicon in the earth’s crust is the most abundant element except oxygen. If carbon is the basis of all organic life, then silicon has the same position for the earth’s crust, because the main part of the earth’s crust is made up of layers of silicon-containing rocks.
These rocks are almost entirely composed of silica and various silicates. Feldspar, mica, clay, olivine, hornblende, etc. are all silicates, crystal, agate, bismuth, opal, quartz, sand and vermiculite are all silica.
There amorphous silicon, and both silicon crystalline allotrope. Crystalline silicon is grayish black and amorphous silicon is black.
The density is 2.32-2.34 g/cm 3, the melting point is 1410 °C, the boiling point is 2355 °C, and the crystalline silicon belongs to atomic crystals. Do not dissolve in water, nitric acid and hydrochloric acid, soluble in hydrofluoric acid and lye. Hard and metallic luster.
Nuclear outer electron distribution: 1s²2s²2p⁶ 3s²3p²
Unit cell type: cubic diamond-type
Unit cell parameters: measured at 20 °C, it is unit cell parameter a = 0.543087 nm
Color and appearance: dark gray, with blue tones.
Using a nanoindentation method, the E of single-crystal silicon (100) is 140 to 150 GPa.
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Conductivity: The electrical conductivity of silicon has a great relationship with its temperature. As the temperature increases, the electrical conductivity increases, reaching a maximum at around 1480 °C, and decreases with increasing temperature after the temperature exceeds 1600 °C.
Silicon has obvious non-metallic properties and can be dissolved in an alkali metal hydroxide solution to produce (partial) silicate and hydrogen.
The silicon atom is located in the main group IV of the periodic table, its atomic number is Z=14, and there are 14 electrons outside the core. The electrons are outside the nucleus, and the energy level is from low silicon atoms to high, from inside to outside, surrounded by layers. silicon uses
This is called the electron shell structure. The first layer of the extranuclear electron of the silicon atom has two electrons, and the second layer has eight electrons, reaching a steady state.
The outermost layer has four electrons, which are valence electrons, which play a leading role in the conductivity of silicon atoms.
Because silicon atoms have such a structure, they have some special properties: the four outer valence electrons make the silicon atoms in a metastable structure.
These valence electrons make the silicon atoms covalently bond with each other due to covalent The bond is relatively strong, silicon has a higher melting point and density, the chemical properties are relatively stable, and it is difficult to react with other substances (except hydrogen fluoride and alkali solution) at normal temperature, there is no obvious free electron in the silicon crystal, which is conductive, but conductive. The rate is inferior to metal and increases with increasing temperature, and has semiconducting properties. silicon uses
Under heating, it can react with elemental halogen, nitrogen, carbon, and other non-metals, and can also interact with certain metals such as Mg, Ca, Fe, Pt. A silicide is formed.
It is insoluble in common inorganic acids, soluble in alkali solution, and has hydrogen evolved to form a corresponding alkali metal silicate solution, which can react with water vapor at red heat temperature.
pure, simple, non-metallic.
(1) Reaction with elemental:
Si + O2 == SiO2, condition: heating
Si + 2F2 == SiF4
Si + 2Cl2 == SiCl4, condition: high temperature
(2) It can react with certain oxides under high temperature vacuum conditions:
2MgO + Si = high temperature vacuum = Mg (g) + SiO2 (silicon thermal reduction magnesium smelting)
(3) Reacts with acid:
Reacts only with hydrofluoric acid: Si + 4HF == SiF4↑ + 2H2↑
(4) Reaction with a base: Si + 2OH − + H2O == SiO32−+ 2H2↑ (eg NaOH, KOH)
Note: Silicon and aluminum are simple substances that can react with acid and react with alkali to release hydrogen.
Si+O2 = high temperature = SiO2
Si + 2OH− + H2O == SiO32−+ 2H2↑
Si+2F2 == SiF4
Si+4HF == SiF4↑+2H2↑
SiO2 + 2OH− == SiO32−+ H2O
SiO32−+ 2NH4++ H2O == H4SiO4↓ + 2NH3↑
SiO32−+ CO2 + 2H2O == H4SiO3↓+ CO32−
SiO32−+ 2H+ == H2SiO3↓
SiO32−+2H++H2O == H4SiO4↓
H4SiO4 == H2SiO3 + H2O
3SiO32−+ 2Fe3+ == Fe2(SiO3)3↓
3SiO32−+2Al3+ == Al2(SiO3)3↓
Na2CO3 + SiO2 = high temperature = Na2SiO3 + CO2 ↑
Silica, Silica gel, Silicate, Silicic acid, Ortho, Silicic acid, Silane, Dichlorosilane,
Atomic weight : 28.0855u.
Quality of nuclear loss: 0.1455u
Atomic radius: (calculated value) 110 (111) pm.
Covalent radius: 111 pm.
Van der Waals radius : 210 pm.
Peripheral electronic layer layout: 3s23p2.
The arrangement of electrons at each energy level: 2, 8, 4
Electronic layer: KLM
Oxidizing (oxide): 4 (amphoteric).
In the laboratory, magnesium powder can be used to reduce the powdered silica under red heat, the formed magnesium oxide and magnesium powder are washed away with dilute acid, and the unacted silica is washed away with hydrofluoric acid to obtain elemental silicon. silicon uses
This method produces amorphous silicon which is not pure enough and is a brown-black powder. Industrial production of silicon is the reduction of silica in an electric arc furnace (SiO2 content greater than 99%).
The reducing agents used are petroleum coke, charcoal, and the like. When a DC arc furnace is used, all of the petroleum coke can be used instead of charcoal.
The petroleum coke has a low ash content (0.3% to 0.8%) and uses high-quality silica (SiO2 greater than 99%) to directly produce high-quality silicon for the production of silicon steel sheets.
High-purity semiconductor silicon can be produced by hydrogen reduction of high-purity trichlorosilane SiHCl3 or SiCl4 on a hot silicon rod of 1,200 °C. Ultrapure single crystal silicon can be prepared by a Czochralski method or a zone melting method or the like.silicon uses
Amorphous silicon can be obtained by reducing silica with magnesium. Crystalline silicon can be obtained by reducing silicon dioxide in an electric furnace with carbon. High-purity silicon used in the electronics industry is produced by reducing Trichlorosilane or silicon Tetrachloride with hydrogen.
- High purity single crystal silicon is an important semiconductor material. A small amount of a Group IIIA element is doped into the single crystal silicon to form a p-type silicon semiconductor; a trace amount of the Group VA element is incorporated to form an n-type semiconductor. The p-type semiconductor and the n-type semiconductor are combined to form a PN junction, which can be made into a solar cell to convert radiant energy into electrical energy. It is a promising material in the development of energy. In addition, widely used diodes, triodes, thyristors, FETs, and various integrated circuits (including chips and CPUs in people’s computers) are made of silicon.
- Metallic ceramics and important materials for space navigation. The ceramic and the metal are mixed and sintered to form a cermet composite material, which is resistant to high temperature, toughness and can be cut, and inherits the respective advantages of the metal and the ceramic, and makes up for the inherent defects of the two. It can be applied to the manufacture of military weapons. The first space shuttle, Columbia, was able to withstand the high temperatures of friction when moving at high speeds through a dense atmosphere, relying on its 31,000 silicon tiles. silicon uses
- Optical fiber communication, the latest modern means of communication. Highly transparent glass fibers can be drawn from pure silica. Instead of a bulky cable, the laser can travel forward in the fiberglass path with numerous total reflections. The fiber-optic communication capacity is high, and a thin fiber can transmit 256 telephones at the same time, and it is not interfered by electricity and magnetism, and is not afraid of eavesdropping, and has high confidentiality. Optical fiber communication will revolutionize the lives of human beings in the 21st century.
- Silicon organic compounds with excellent performance. For example, silicone plastic is an excellent waterproof coating material. Spraying silicone on the walls of the underground railway can solve the problem of water seepage once and for all. In the appearance of ancient artifacts and sculptures, a thin layer of silicone plastic can be applied to prevent the growth of moss and resist wind, rain, and weathering. The Monument to the People’s Heroes on Tiananmen Square is treated with silicone plastic, so it is always white and fresh.
- Due to the unique structure of organic silicon, it has the properties of inorganic materials and organic materials. It has the basic properties of low surface tension, small viscosity coefficient, high compressibility, and high gas permeability. It has high-temperature resistance, electrical insulation, and resistance. Excellent properties such as oxidative stability, weather resistance, flame retardancy, water repellency, corrosion resistance, non-toxicity, tastelessness, and physiological inertness. It is widely used in aerospace, electrical and electronics, construction, transportation, chemical, textile, food, light industry, medical, etc. The industry, in which silicone is mainly used for sealing, bonding, lubrication, coating, surface activity, remolding, deforming, foam suppression, waterproof, moisture, inert filling and so on. With the continuous growth of the number and variety of organic silicon, the application field has been continuously expanded to form an important product system unique to the chemical new materials industry. Many varieties are indispensable and indispensable for other chemicals.
- Silicon can increase the hardness of plant stems and increase the difficulty of feeding and digesting pests. Although silicon is not an essential element in plant growth and development, it is also a chemical element necessary for plants to resist stress and regulate the relationship between plants and other organisms.
Silicon has a great role in improving plant resistance to abiotic and biological stresses, such as silicon, which can increase plant resistance to drought, salt stress, ultraviolet radiation, and pests and diseases. silicon uses
Silicon can improve the resistance of rice to Cnaphalocrocis medinalis. After applying silicon, the defense response of rice to pests is rapidly increased, and silicon plays a guard role against plant defense.
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When rice is attacked by insects, silicon can guard against the rapid activation of the jasmonic acid pathway associated with stress resistance. The jasmonic acid signal, in turn, promotes the absorption of silicon. The interaction between silicon and jasmonic acid signaling pathway affects the resistance of rice to pests.
Silicon is one of the essential trace elements in the human body. It accounts for 0.026% of body weight. The biggest harm to silicon and silicon-containing dust is to cause silicosis. Silicosis is one of the serious occupational diseases. silicon uses
Miners, stone processing workers, and other workers in places containing silicon dust should take necessary protective measures.
Silicon is essential for connective tissue and cartilage formation. Silicon can bind mucopolysaccharides to each other and bind the mucopolysaccharide to proteins to form a fibrous structure, thereby increasing the elasticity and strength of connective tissue and maintaining structural integrity.
Silicon is involved in the calcification of bone and plays a role in the initial stage of calcification. Silicon in food can increase the rate of calcification, especially when the calcium intake is low.
The amino acid in collagen is about 21% hydroxyproline. Aminoacyl hydroxylase hydroxylates proline, which requires silicon when it exhibits maximum viability; by analyzing collagen from different sources, it is shown that silicon is one of the constituents of collagen. silicon uses
Reference intake: Since there is no experimental data on the amount of silicon required by the human body, it is difficult to propose a suitable daily demand for silicon in the human body.
It is estimated from animal experiments that if the silicon is easily absorbed, the daily demand of the human body maybe 2 to 5 mg. However, most of the silicon in the diet is not easily absorbed.
The recommended intake is about 5-10 mg per day. It can be considered that a daily intake of 20-50 mg is suitable.
Excessive performance: Patients with high silicon disease and high silicon diet have found focal glomerulonephritis and individuals with significantly increased silicon in kidney tissue. silicon uses
It has also been reported that a large amount of magnesium silicate (silicon-containing antacid) may induce urinary calculi in humans.
Silicosis, long-term inhalation of a large amount of silicon-containing dust through the respiratory tract can cause silicosis.
Silicosis, also known as silicosis, is one of the most common types of pneumoconiosis. It is a disease characterized by extensive nodular fibrosis in the lungs caused by long-term inhalation of a large amount of free silica dust.
Silicosis patients suffer from extensive micro fibrotic hyperplasia of the lungs due to impaired microvascular circulation in both lungs, and the resistance is reduced, so it is easy to merge with other diseases, leading to worsening of the disease and even death. silicon uses
Insufficient performance: lack of silicon in the feed can make the animal grow slow, lack of hair, nails are easy to break, and the skin loses luster.
Animal test results show that feeding the arteriosclerotic drink while supplementing silicon helps to protect the structure of the animal’s aorta.
In addition, it has been determined that the silicon content in the vessel wall is inversely proportional to the degree of atherosclerosis in humans and animals.
Among the two groups with a long-term difference in cardiovascular disease, the silicon content in drinking water is also about twice as high, and people with high drinking water silicon content are less likely to suffer.
Silicon is a very safe substance. It does not react with the immune system itself and is not swallowed by cells. It does not breed bacteria or react with chemicals.
At the same time, it can also be used to produce silica gel for skin wounds. To protect the wound, it is a very safe material and is approved by the health authorities of various countries.