Analysis:
Discovery history of boron
Although people have been dealing with boron for a long time, for example, borax was used as a flux when making glass in ancient Egypt, and it was also used by ancient alchemists, but the chemical composition of boric acid was still a mystery at the beginning of19th century.
1808, British chemist Sir humphry davy (1778- 1829) discovered potassium by electrolysis, and then made brown boron from electrolytic molten boron trioxide. In the same year, French chemists Joseph-Louis Grey-Lussac (1778- 1850) and Louis Jacques Nader (1777- 1857) reduced the anhydrous boric acid to produce boron. Boron is named boron, and its name comes from the word * * *, which means "flux". It shows that ancient people have known that borax has the ability to melt metal oxides and is used as a flux in welding.
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boron
Boron, atomic number 5, atomic weight 10.5438+0 1. Around 200 BC, ancient Egypt, Rome and Babylon used borax to make glass and weld gold. 1808, French chemists Gay-Lussac and Seinard respectively reduced boric acid with metallic potassium to produce elemental boron. The content of boron in the crust is 0.00 1%. There are two isotopes of natural boron: boron 10 and boron 1 1, of which boron 10 is the most important.
Boron is a black or silver-gray solid. Crystal boron is black, with a melting point of about 2300°C, a boiling point of 2550°C and a density of 2.34 g/cm? Hardness is second only to diamond, and it is fragile.
Boron is relatively stable at room temperature, even if it is cooked in hydrochloric acid or hydrofluoric acid for a long time. Boron can be directly combined with halogen elements to form boron halide. Boron can react with sulfur, tin, phosphorus and arsenic at 600 ~ 1000℃; At 1000 ~ 1400℃, boron reacts with nitrogen, carbon and silicon, and also reacts with many metals and metal oxides at high temperature to form metal borides. These compounds are usually substances with high hardness, melting resistance, high conductivity and chemical inertness, and often have special properties.
Boron is widely used. Boron combined with plastic or aluminum alloy is an effective neutron shielding material; Boron steel is used as a control rod in reactors; Boron fibers are used to make composite materials.
Element name: boron
Atomic weight of the element: 10.6438+0.
Element type: nonmetal
Atomic number: 5
Element symbol: b
Chinese name of element: boron
English name of element: boron
Relative atomic mass: 10.438+0.
Number of protons in the nucleus: 5
Number of extranuclear electrons: 5
Number of nuclear power audits: 5
Proton mass: 8.365E-27
Proton relative mass: 5.035
Period: 2
Number of families: IIIA
Molar mass: 1 1
Hydride: BH3
Oxide: B2O3
The chemical formula of the highest valence oxide is B2O3.
Density: 2.34
Melting point: 2300.0
Boiling point: 2550.0
Peripheral electronic configuration: 2s2p 1
Extranuclear electron configuration: 2,3
Color and state: solid state
Atomic radius: 1. 17
Ordinary valence: +3
Discovers: David, Grusack and Tanner. Discovery date: 1808.
Discovery process:
1808, David in Britain, Grusack and Tanner in France reduced boric acid with potassium to produce boron.
Element description:
It is the only nonmetallic element with less than 4 electrons in the outermost layer. There are two kinds of simple substances: amorphous and crystalline. The former is brownish black to black powder. The latter is black to silver gray with metallic luster. Hardness is similar to that of diamonds. The density of amorphous boron is 2.3g/cm3 (25-27℃); The density of boron in crystal form is 2.3 1g/cm3, the melting point is 2300℃, the boiling point is 2550℃, and the valence is 3. Amorphous boron slowly oxidizes in air at room temperature and can spontaneously ignite at about 800℃. Boron and hydrochloric acid or hydrofluoric acid, even if cooked for a long time, have no effect. It can be slowly eroded and oxidized by hot concentrated nitric acid and the mixture of sodium dichromate and sulfuric acid. Hydrogen peroxide and ammonium persulfate can also slowly oxidize crystalline boron. The reagent reacts strongly with amorphous boron. All forms of boron are completely oxidized when melted with the mixture of alkali metal carbonate and hydroxide. Chlorine, bromine and fluorine react with boron to form corresponding boron halides. At about 600℃, boron reacts violently with sulfur to form boron sulfide mixture. When boron is heated to above 1000℃ in nitrogen or ammonia, boron nitride is formed. Boron and hydrogen do not react at 1800-2000℃, while boron and silicon react above 2000℃ to form silicon boride. At high temperature, boron can react with many metals and metal oxides to form metal borides.
Source of elements: In nature, boron only exists in the form of its compounds (such as borax and boric acid, and only a small amount of boron exists in animals and plants), and is usually prepared by electrolytic melting of potassium fluoborate and potassium chloride or thermal reduction of other compounds (such as boron oxide).
The preparation method comprises: thermally reducing boron oxide with active metal; Reducing boron halide with hydrogen; Reduction of borax by carbothermal reduction; Electrolytic melting of borate or other boron-containing compounds; Thermal decomposition of hydrogen compounds of boron The primary product obtained by the above method should be degassed in vacuum or controlled halogenation to prepare high-purity boron.
Element uses: Because of its strong neutron absorption ability, it is mainly used in metallurgy (such as increasing the hardness of steel) and nuclear science.
Because boron is particularly active at high temperature, it is used as metallurgical degassing agent, heat treatment of forged iron and increasing the high temperature strength of alloy steel. Boron is also used in atomic reactors and high temperature technology. Boron steel bars and bars are widely used as control rods in atomic reactors. Because of its low density, high strength and high melting point, boron can be used to make some structural materials used in missile rockets. Boron compounds are widely used in agriculture, medicine and glass industry.
Element auxiliary data:
Borax (Na2B4O7 10H2O) is a natural boron-containing compound, which has long been known by ancient physicians. China is a country rich in borax resources in the world.
1702, the French doctor Holmberg first prepared boric acid from borax, which is called salsedativum, that is, sedative salt. 174 1 year, French chemist Pat pointed out that borax reacts with sulfuric acid to produce boric acid and sodium sulfate. 1789, lavoisier listed the boric acid family in the element list. 1808, British chemist David and French chemists Grusack and Tanner each obtained the element boron. The Latin name of boron is boracium, and the element symbol is B. This word comes from borax.
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