What is silicon in simple words?

Silicon is an element (non-metal) located in the main subgroup of the fourth group, the third period. It has atomic number fourteen. It also has its own symbol – Si (Silicium). At the beginning of the eighteenth century, the French chemist Joseph Louis Gay-Lussac and his colleague Louis Jacques Thénard obtained silicon in its pure form. Later, the Swedish scientist Jöns Jakob Berzelius also derived elemental silicon and called it “silicium” (translated from Latin silex – flint). In Russia, the official name “silicon” was introduced by G.I. Hess in the thirties of the 18th century, which translated from ancient Greek (κρημνός) means “mountain, cliff.” Free silicon is formed when white sand (SiO₂) with magnesium (Mg): [SiO]₂ + 2Mg=2MgO + Si, where silicon is a brown powder. In the metallurgical industry, silicon is obtained in the following way: molten silicon dioxide is reduced using coke at a temperature of approximately one thousand eight hundred degrees Celsius in ore-thermal shaft furnaces. After such a process, the purity of silicon is 99,9% (the main impurities are metal and carbon). In the future, silicon can be cleaned of impurities again. In laboratories, silicon purification occurs as follows: first, Mg is obtained₂Si, then gaseous SiH is made from magnesium silicide using acetic or hydrochloric acid₄. The resulting monosilane is subjected to purification, for example, sorption or rectification, or other methods. Finally SiH₄ decompose into hydrogen and silicon at a temperature of approximately one thousand degrees Celsius. In industry, silicon is purified using a chlorination process. Thanks to this, two compound compounds appear – SiCl₃, as well as SiCl₄H. Such chlorides can remove impurities in various ways. And the very last stage is the reduction of pure hydrogen – the temperature should be about nine hundred or one thousand one hundred degrees Celsius. Silicon purifications are being developed that are more effective, cleaner, and inexpensive. By 2010, silicon purification was carried out, which used fluorine (chlorine was changed to fluorine); technologies have been developed that involve silicon monoxide distillation; Technologies have been invented that are based on the etching of impurities, which, as a rule, are concentrated at the boundaries between grains (crystallites). In the crude state, silicon impurities have a mass reduced by 10-8 – 10-6%. Silicon (technical) is produced in some Russian cities, such as Kamensk-Uralsky and Shelekhov. At the Usolye-Sibirsky plant, using (chloride) technology, highly purified silicon is produced by the group “Nitol Solar”. Technical silicon is used: 1. In metallurgical production as:
– one of the components of the bronze alloy, silumin;
– deoxidizing agent for steel and cast iron smelting;
– alloying element, modifier;
2. As a raw material for the production of polysilicon (a material consisting of small silicon crystallites).
3. In the production of silanes, as well as organosilicon materials.
4. In field conditions during hydrogen production.
5. In the manufacture of solar panels.
6. In the plastics industry as an antiblock (additive). Silicon is also used to produce passive elements of electrical circuits, as well as for the production of monolithic microcircuits. The main components of the production of solar cells, in addition to pure silicon, are its waste, as well as crystalline silicon. Monocrystalline silicon is used in the production of electronics and gas laser mirrors. Silicides (silicon compounds with metals) are often used in the nuclear and electronics industries. They have a large number of useful properties, for example, resistance to oxidation, neutrons, etc. For thermoelectricity, silicides of a number of elements are one of the most important materials. Silicon compounds are the basis for the production of cement and glass. Their production, as well as the production of ceramics and other things made from brick, porcelain, etc., is carried out by the silicate industry. Glue made from silicate is very popular in the world; it is used as a “drying agent” in construction and in pyrotechnic production to glue paper. Silicon is located in main subgroup of group IV (or in group 14 in the modern form of PSHE) and in third period periodic system of chemical elements D.I. Mendeleev.

Electronic structure of silicon

Electronic configuration silicon в ground state : +14Si 1s 2 2s 2 2p 6 3s 2 3p 2 Electronic configuration silicon в excited state : +14Si * 1s 2 2s 2 2p 6 3s 1 3p 3 The silicon atom contains at the outer energy level 2 unpaired electrons and 1 lone electron pair in the ground energy state and 4 unpaired electrons in an excited energy state. The oxidation states of the silicon atom are from -4 to +4. Characteristic oxidation states are -4, 0, +2, +4.

Physical properties, methods of production and occurrence of silicon in nature

Silicon is the second most abundant element on Earth after oxygen. Found only in the form of compounds. Silicon oxide SiO₂ forms a large amount of natural substances – rhinestone, quartz, silica. The simple substance silicon – atomic crystal dark gray with a metallic sheen, quite fragile. Melting point 1415 °C, density 2,33 g/cm3. Semiconductor.

Qualitative reactions

Qualitative response to silicate ions SiO₃ 2- – interaction silicate salts with strong acids . Silicic acid is weak. It is easily isolated from solutions of silicic acid salts when exposed to stronger acids. For example , if a highly dilute solution is added to a sodium silicate solution of hydrochloric acidthen silicic acid will be released not as a precipitate, but as gel. The solution will become cloudy and “harden”. Na₂SiO₃ + 2HCl = H₂SiO₃ + 2 NaCl Video experience The interaction of sodium silicate with hydrochloric acid (production of silicic acid) can be viewed here.

Silicon compounds

The main oxidation states of silicon are +4, 0 and -4. The most typical silicon compounds are:

Oxidation state	Typical connections
+4	silicon(IV) oxide SiO2

Methods for obtaining silicon

Silicon was obtained in a free state by Berzelius in 1822. Its Latin name “silicium” comes from the Latin word “sile x”, which means “flint”. Amorphous silicon in the laboratory can be obtained by calcining a mixture of metal magnesium с silicon dioxide. For the experiment, silicon dioxide should be thoroughly ground. When the mixture is heated, a violent reaction begins. One of the products of this reaction is amorphous silicon. SiO₂ + 2Mg → Si + 2MgO Video experience the interaction of silicon (IV) oxide with magnesium can be viewed here. Another way to obtain silicon in the laboratory – reduction from oxide aluminum: In industry using expensive aluminum and magnesium is ineffective, so other, cheaper methods are used: 1. Reduction from oxide coke in electric ovens: SiO₂ + 2C → Si + 2CO However, in this process, the resulting silicon is contaminated with impurities of silicon carbides, and is no longer suitable for the production of, for example, microcircuits. 2. The purest silicon is obtained by reduction of silicon tetrachloride hydrogen at 1200 °C: SiCl₄ + 2H₂ → Si + 4HCl or zinc : SiCl₄ + 2Zn → Si + 2ZnCl₂ 3. Pure silicon is also obtained by decomposition silane :

Chemical properties

Under normal conditions, silicon exists in the form of an atomic crystal, so the chemical activity of silicon is extremely low. 1. Silicon exhibits properties oxidizing agent (when interacting with elements that are located below and to the left in the Periodic Table) and properties reducing agent (when interacting with elements located above and to the right). Therefore, silicon reacts with metals , And non-metals . 1.1. Under normal conditions, silicon reacts with fluorine with education silicon(IV) fluoride: When heated, silicon reacts с chlorine, bromine, iodine : 1.2. When heated strongly (about 2000 o C), silicon reacts с carbon to form a binary compound silicon carbide (carborundum): C + Si → SiC At temperatures above 600°C it interacts with sulfur: Si + 2S → SiS₂ 1.3. Silicon does not interact с hydrogen . 1.4. With nitrogen silicon reacts under very harsh conditions: 1.5. In reactions with active metals silicon exhibits properties oxidizing agent. In this case, silicides: 2Ca + Si → Ca₂Si Si + 2Mg → Mg₂Si 1.6. When heated above 400°C, silicon interacts with oxygen : 2. Silicon interacts with complex substances: 2.1. In aqueous solutions alkalis silicon dissolves to form salts silicic acid. In this case, the alkali oxidizes silicon. 2.2. Silicon does not interact with aqueous acid solutions , but amorphous silicon dissolves in hydrofluoric acid with the formation of hexafluorosilicic acid: When silicon is treated with anhydrous hydrogen fluoride, the complex does not form: Silicon reacts with hydrogen chloride at 300 °C, with hydrogen bromide at 500 °C. 2.3. Silicon dissolves in mixtures of concentrated nitric and hydrofluoric acids : 3Si + 4HNO₃ + 12HF → 3SiF₄ + 4NO + 8H₂O

Binary silicon compounds

Metal silicides

Silicides – These are binary compounds of silicon with metals, in which silicon has an oxidation state of -4. The chemical bond in metal silicides is ionic. Silicides are usually easily hydrolyze in water or in an acidic environment. For example , magnesium silicide decomposes with water into magnesium hydroxide и silane: Hydrochloric acid easily decomposes magnesium silicide: Silicides are obtained by fusing simple substances or reducing a mixture of oxides coke in electric furnaces: 2Mg + Si → Mg ₂ Si 2MgO + SiO₂ + 4C → Mg₂Si + 4CO

Silan

Silan is a binary compound of silicon and hydrogen SiH₄, a poisonous colorless gas. If you put the powder magnesium silicide in a very weak solution of hydrochloric acid, then gas bubbles form on the surface of the solution. They burst and catch fire in the air. It’s burning silane. It is formed by the reaction of acid with magnesium silicide: Video experience obtaining silane from magnesium silicide can be found here. Airborne silane Burns with the formation of SiO₂ and H₂O: Video experience combustion of silane can be viewed here. Silan decomposes with water decomposes with the release of hydrogen: Silane decomposes (oxidizes) alkalis : Silane when heated decomposes :

Silicon carbide

In compounds of silicon with non-metals there is a covalent bond. Consider silicon carbide – carborundum Si +4 C -4 . This is a substance with an atomic crystal lattice. It has a structure similar to that of diamond and is characterized by high hardness and melting point, as well as high chemical resistance. Carborundum oxidizes oxygen at high temperature: Carborundum oxidizes oxygen in the melt alkalis :

Silicon halides

Silicon chloride and fluoride are silicic acid halides.
SiCl₄. Silicon halides are prepared by chlorine for alloy silicon oxide с coal : Silicon halides decompose water to silicic acid и hydrogen chloride: Silicon(IV) chloride is reduced hydrogen : SiCl₄ + 2H₂ → Si + 4HCl

Silicon(IV) oxide

Physical properties and occurrence in nature

Silicon(IV) oxide is a solid substance with an atomic crystal lattice. It occurs in nature in the form of quartz, river sand, silica and other modifications:

Chemical properties

Silicon(IV) oxide – typical acid oxide . Due to silicon with an oxidation state of +4, it exhibits weak oxidative properties. 1. As an acidic oxide, silicon dioxide (IV) reacts with solutions and melts alkalis and in melt with basic oxides . In this case, silicates. For example , silicon dioxide interacts with potassium hydroxide: Others example : Silicon dioxide reacts with calcium oxide. SiO₂ + CaO → CaSiO₃ 2. Silicon(IV) oxide does not react с водой , because silicic acid is insoluble. 3. Silicon(IV) oxide reacts when fused with alkali metal carbonates . The rule works: the less volatile oxide displaces the more volatile oxide from the salts upon fusion. For example , silicon(IV) oxide reacts with potassium carbonate. This produces potassium silicate and carbon dioxide: 4. Of the acids, silicon dioxide reacts only with fluorescent or with hydrogen fluoride gas : 5. At temperatures above 1000 °C, silicon oxide reacts with active metals, in this case silicon is formed. For example , silicon oxide interacts with magnesium with education silicon и magnesium oxide: SiO₂ + 2Mg → Si + 2MgO Video experience the interaction of silicon (IV) oxide with magnesium can be viewed here. When there is an excess of reducing agent, silicides: SiO₂ + 4Mg → Mg₂Si + 2MgO 6. Silicon(IV) oxide reacts with non-metals. For example , silicon(IV) oxide reacts with hydrogen in harsh conditions. In this case, silicon oxide exhibits oxidizing properties: Others example : silicon oxide interacts with carbon. This creates carborundum и carbon monoxide: SiO₂ + 3С → SiС + 2СО When fused, silicon oxide interacts with calcium phosphate и coal:

Silicic acid

Molecule structure and physical properties

Silicic acids – very weak, slightly soluble in water compounds of the general formula nSiO₂•mH₂O. Forms a colloidal solution in water. Metasilicon H₂SiO₃ exists in solution as a polymer:

Methods of obtaining

Silicic acid is formed by the action of strong acids on soluble silicates (alkali metal silicates). For example , during action of hydrochloric acid on sodium silicate: Na ₂ SiO ₃ + 2 HCl → H ₂ SiO ₃ + 2 NaCl Video experience obtaining silicic acid from sodium silicate can be found here. Even weak carbonic acid displaces silicic acid from salts:

Chemical properties

1. Silicic acid is insoluble. The acid properties are very weak, so the acid reacts only with strong reasons and their oxides : For example , silicic acid reacts with concentrated potassium hydroxide: 2. When heated, silicic acid decomposes for oxide and water :

Silicates

Silicates – These are salts of silicic acid. Most silicates are insoluble in water, except sodium silicates и potassium, they are called “liquid glass”. Methods of obtaining silicates: 1 . Dissolving silicon, silicic acid or oxide in alkali: 2. Fusion with basic oxides: CaO + SiO₂ →CaSiO₃ 3. Interaction of soluble silicates with salts: Window glass (sodium glass) – sodium and calcium silicate: Na₂O CaO 6SiO₂. Glass is obtained by fusing a mixture of sodium soda in special furnaces₂CO₃, limestone CaCO₃ and white sand SiO₂: To get special glass various additives are introduced, such as glass containing Pb 2+ ions – crystal; Cr 3+ – has a green color, Fe 3+ – brown bottle glass, Co 2+ – gives a blue color, Mn 2+ – reddish-purple.