The beryllium sheet produced by the vacuum hot pressing and rolling process has excellent permeability to X-rays and other rays, so the beryllium sheet can be used as a window material for X-ray tubes, detectors and low-energy photon sources. The beryllium sheet produced by the vacuum hot pressing and rolling process has excellent permeability to X-rays and other rays, so the beryllium sheet can be used as a window material for X-ray tubes, detectors and low-energy photon sources.
The chemical properties of beryllium are active and can form a dense surface oxidation protection layer. Even in the red heat, beryllium is very stable in the air. Beryllium can not only react with dilute acid, but also dissolve in strong alkali, showing amphoteric. Beryllium oxides and halides have obvious covalent properties. Beryllium compounds are easily decomposed in water, and beryllium can also form polymers and covalent compounds with obvious thermal stability.
The chemical properties of beryllium
Beryllium, like lithium, forms a protective oxide layer in the air, so it is stable even when it is red hot in the air. Insoluble in cold water, slightly soluble in hot water, soluble in dilute hydrochloric acid, dilute sulfuric acid and potassium hydroxide solution to release hydrogen. Metal beryllium has obvious corrosion resistance to oxygen-free sodium metal even at higher temperatures. The valence state of beryllium is +2, which can form polymers and a class of covalent compounds with remarkable thermal stability.
First ionization energy 899.5 kJ/mol
Second ionization energy 1757.1 kJ/mol
The third ionization energy 14848.7 kJ/mol
7Be artificial 53.12 days electron capture 0.862 7Li
9Be 100% stable
10Be trace 1.51×106 years β decay 0.556 10B
The valence electron layer structure of Be atom is 2s2, its atomic radius is 89 pm, Be2+ ion radius is 31 pm, and the electronegativity of Be is 1.57. Because beryllium has a very small atomic radius and ionic radius, and relatively high electronegativity, beryllium has a significant tendency to form covalent bonds, unlike other elements of the same family, which mainly form ionic compounds. Therefore, beryllium often exhibits anomalous properties different from other elements of the same group.
(1) Beryllium tends to form a dense protective film on the surface and does not interact with water, while other metals of the same family, magnesium, calcium, strontium, and barium, all easily react with water.
(2) Beryllium hydroxide is amphoteric, while the hydroxides of other elements of the same group are medium-strong or strong alkaline.
(3) The beryllium salt strongly hydrolyzes to generate tetrahedral ions [Be(H2O)2]2+. The Be-O bond is very strong, which weakens the O-H bond, so the hydrated beryllium ion has a tendency to lose protons:
Therefore, beryllium salt is acidic in pure water. The salts of other elements of the same family (except magnesium) have no hydrolysis.
鈹?shù)纳晌?/span>
1. Beryllium oxide
Beryllium BeO, its melting point is 2803K, is hard to dissolve in water, and it is not easy to dissolve in ethanol. It can be used as high temperature resistant material. BeO is covalent and has a 44 zinc sulfide (sphalerite) structure. BeO is insoluble in water, but soluble in beryllium salt produced by acid and beryllium salt produced by alkali. BeO is an amphoteric oxide.
2. Beryllium hydroxide
Beryllium BeO, its melting point is 2803K, is hard to dissolve in water, and it is not easy to dissolve in ethanol. It can be used as high temperature resistant material. BeO is covalent and has a 44 zinc sulfide (sphalerite) structure. BeO is insoluble in water, but soluble in beryllium salt produced by acid and beryllium salt produced by alkali. BeO is an amphoteric oxide.
Beryllium hydroxide is a white solid with low solubility in water. It is an amphoteric hydroxide. It dissolves in acid to form Be2+, ??and dissolves in alkali to form [Be(OH)4]2-
3. Beryllium Hydride
Be cannot directly combine with H2 to produce beryllium hydride, but beryllium hydride can be produced by reducing beryllium chloride with lithium aluminum hydride.
Beryllium hydride is a covalent compound whose structure is similar to that of diborane, forming a hydrogen bridge bond between two Be atoms.
Each Be atom is connected to four H atoms, and each H atom generates two bonds. Since the Be atom has only two valence electrons, there are not enough electrons in beryllium hydride to form a normal electron pair bond (that is, two electrons are shared between two atoms). Beryllium hydride is an electron-deficient compound. Therefore, in the Be-H-Be bridge bonding, a "banana-shaped" three-center two-electron bond is formed. This is a cluster compound.
Application areas of beryllium
Beryllium has been paid more and more attention as an emerging material. Beryllium is an indispensable and precious material in atomic energy, rockets, missiles, aviation, astronautics and metallurgical industries.
(1) Among all metals, beryllium has the strongest ability to transmit X-rays and is known as metallic glass. Therefore, beryllium is an irreplaceable material for the manufacture of small windows in X-ray tubes.
(2) Beryllium is the treasure of the atomic energy industry. In atomic reactors, beryllium is a neutron source that can provide a large number of neutron shells (can produce hundreds of thousands of neutrons per second); beryllium has a strong decelerating effect on fast neutrons, which can make fission reactions continuous The ground continues, so beryllium is the best neutron moderator in nuclear reactors. In order to prevent neutrons from running out of the reactor and endangering the safety of the staff, there must be a neutron reflecting layer around the reactor to force those neutrons that attempt to escape from the reactor to return to the reactor. The oxide of beryllium can not only reflect the neutrons back like a mirror, but also has a high melting point and is particularly resistant to high temperatures. It is the best material for the neutron reflection layer in the reactor.
(3) Beryllium is an excellent aerospace material. For every kilogram of the weight of the artificial satellite, the total weight of the launch vehicle will increase by about 500kg. The structural materials used to manufacture rockets and satellites require light weight and high strength. Beryllium is lighter than commonly used aluminum and titanium, and its strength is four times that of steel. Beryllium has strong heat absorption capacity and stable mechanical properties.
(4) In the metallurgical industry, the bronze containing 1% to 3.5% of beryllium is called beryllium bronze, which has better mechanical properties than steel, good corrosion resistance, and high electrical conductivity. It is used to make hairsprings in watches, high-speed bearings, and submarine cables.
(5) Beryllium bronze containing a certain amount of nickel does not produce sparks when impacted. This wonderful property can be us
