Silicon is a chemical element, its chemical symbol is Si, formerly known as silicon. Atomic number 14, relative atomic mass 28.0855, with amorphous silicon and crystalline silicon two kinds of allotropes, belonging to the periodic table on the third cycle, IVA family of metal elements. Silicon is also a very common element, but it rarely appears in the form of simple matter in nature, but in the form of complex silicate or silica, widely present in the rock, gravel, dust. Silicon in the universe in the reserves ranked eighth. In the crust, it is the second rich element, constituting 26.4% of the total mass of the crust, second only to the first oxygen (49.4%).
Silicon has a distinct nonmetal property that can be dissolved in an alkali metal hydroxide solution to produce (partial) silicates and hydrogen.
The silicon atom is located in the IV family of the periodic table. Its atomic number is Z = 14 and there are 14 electrons outside the nucleus. Electrons in the nucleus, according to the energy level from the low silicon atoms to high, from the inside to the outside, surrounded by layers, which is called the electronic shell structure. The outer layer of the outer electrons of the silicon atom has two electrons, and the second layer has eight electrons to reach a steady state. The outermost layer has four electrons that are valence electrons, which play a leading role in the conductivity of silicon atoms.
It is precisely because the silicon atoms have such a structure, so there are some special properties: the outermost four valence electrons to silicon atoms in the sub-stable structure, the valence electrons so that the covalent bond between the silicon atoms, due to covalent Bond is relatively strong, silicon has a high melting point and density; chemical properties are relatively stable, it is difficult at room temperature with other substances (in addition to hydrogen fluoride and lye outside the reaction; silicon crystal is not obvious free electrons, can be conductive, but conductive Less than the metal, and with the increase in temperature, with the nature of the semiconductor.
Heating with the elemental halogen, nitrogen, carbon and other non-metallic role, but also with some metals such as Mg, Ca, Fe, Pt and so on. To produce silicides. Insoluble in the general inorganic acid, soluble in alkaline solution, and the release of hydrogen, the formation of the corresponding alkali metal silicate solution, at the red hot temperature, and water vapor can play a role.
1, high purity monocrystalline silicon is an important semiconductor material. A small amount of a Group IIIA element is incorporated in the monocrystalline silicon to form a p-type silicon semiconductor; a trace amount of a Group VA element is incorporated to form an n-type semiconductor. p-type semiconductor and n-type semiconductor together to form p-n junction, can be made of solar cells, the radiation energy into electricity. In the development of energy is a very promising material. Also widely used in the diode, transistor, thyristor, FET and a variety of integrated circuits (including people inside the computer chips and CPU) are made of silicon raw materials.
2, cermet, an important material for aerospace navigation. The ceramic and metal mixed sintering, made of cermet composite, it is high temperature, toughness, can be cut, both inherited the advantages of metal and ceramics, but also make up for both the inherent defects. Can be applied to the manufacture of military weapons. The first space shuttle "Columbia" can withstand high-speed wear through the dense atmosphere of friction generated by the high temperature, thanks to it that thirty thousand one thousand silicon tile fight into the shell.
3, optical fiber communication, the latest modern means of communication. With pure silica can be drawn out of high transparency of glass fiber. Laser can be in the glass fiber path, the occurrence of countless total reflection and forward transmission, instead of the cumbersome cable. Fiber optic communication capacity is high, a hair so fine glass fiber, you can simultaneously transmit 256 phone; and it is not affected by electricity, magnetic interference, not afraid of eavesdropping, with a high degree of confidentiality. Fiber communication will make the 21st century human life revolution.
4, excellent performance of silicon organic compounds. 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 ancient artifacts, sculpture appearance, coated with a thin layer of silicone plastic, can prevent the moss breeding, against wind and rain and weathering. Tiananmen Square, the People's Heroes Monument, is treated by silicone plastic surface, so always white, fresh.
5, due to the unique structure of silicone, both inorganic materials and organic materials performance, with a low surface tension, viscosity coefficient is small, high compressibility, high gas permeability and other basic properties, and has high and low temperature, electrical insulation, It is widely used in aerospace, electrical and electronic, construction, transportation, chemical industry, textile, food, light industry, medical treatment and so on. It is widely used in aerospace, electronic stability, weather resistance, flame resistance, hydrophobic, corrosion resistance, non-toxic and tasteless and physiological inertness. Industry, which is mainly used in silicone sealing, bonding, lubrication, coating, surface activity, stripping, defoaming, foam suppression, waterproof, moisture, inert filling. With the continuous growth of the number and variety of organic silicon, the application field has been widened to form an important product system which is unique in the new materials industry. Many varieties are indispensable and indispensable for other chemicals.
6, silicon can increase the hardness of plant stalk, pest feeding and digestion to increase the difficulty. Although silicon is not an essential element in plant growth and development, it is also a chemical element necessary for plants to resist adversity and regulate the relationship between plants and other organisms.
Silicon has a great effect on improving plant resistance to abiotic and biotic stress. For example, silicon can improve the resistance of plants to drought, salt stress, ultraviolet radiation and pests and diseases. Silicon can improve the resistance of rice to Cnaphalocrocis medinalis. After applying silicon, the defense response of pests to pests increases rapidly, and silicon plays a protective role in plant defense.
When the rice is attacked by pests, the silicon can guard the rice quickly