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 significant corrosion resistance to oxygen-free sodium metal even at higher temperatures. Beryllium is in the +2 valence state and can form polymers as well as a class of covalent compounds with significant thermal stability.
Anomalous Properties Of Beryllium
The valence electron shell structure of Be atom is 2s2, its atomic radius is 89pm, the Be2+ ionic radius is 31pm, and the electronegativity of Be is 1.57. Beryllium has a relatively small atomic radius and ionic radius, and relatively high electronegativity, so beryllium has a relatively significant tendency to form covalent bonds, unlike other elements of the same family, which mainly form ionic compounds. Therefore, beryllium often exhibits anomalous properties that are different from other elements of the same family.
- Beryllium is easy 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, are easy to react with water.
- Beryllium hydroxide is amphoteric, while the hydroxides of other elements in the same family are medium or strong alkaline.
- Beryllium salts are strongly hydrolyzed to form tetrahedral ions [Be(H2O)2]2+, and the Be-O bond is strong, which weakens the O-H bond, so the hydrated beryllium ion has a tendency to lose protons: so beryllium salts It is acidic in pure water. The salts of other elements of the same family (except magnesium) have no hydrolysis effect.
1. Beryllium Oxide
Beryllium burning in oxygen, or beryllium carbonate, nitrate, hydroxide heating and decomposing, can get white powdery beryllium oxide BeO, its melting point is 2803K, insoluble in water, not easily soluble in ethanol , can be used as high temperature resistant material. BeO is covalent and has a zinc sulfide (sphalerite) structure of 44. BeO is insoluble in water, but soluble in beryllium salts generated by acids and beryllium salts generated by alkalis. BeO is an amphoteric oxide.
2. Beryllium Hydroxide
Beryllium hydroxide is a white solid with low solubility in water. It is an amphoteric hydroxide that 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 form beryllium hydride, but beryllium hydride can be obtained 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 between two Be atoms.
Each Be atom is linked to four H atoms, and each H atom creates two bonds. Since the Be atom has only 2 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), and beryllium hydride is an electron-deficient compound. Therefore, in the Be-H-Be bridge bonding, a “banana-shaped” three-center two-electron bond is generated. This is a cluster compound.
4. Beryllium Chloride
Beryllium chloride is a covalent compound that absorbs moisture in the air and emits fumes due to hydrolysis:
BeCl2+H2O=BeO+2HCl
Beryllium chloride sublimates and does not conduct electricity. Anhydrous beryllium chloride is polymeric (BeCl₂)₂.
5. Beryllium Sulfide
Beryllium sulfide (BeS) is an off-white powder with a relative density of 2.36. It can be obtained by reacting beryllium chloride and anhydrous hydrogen sulfide.
6. Beryllium Carbide
Beryllium carbide (Be2C) is a yellow-red solid that decomposes in contact with water. It is obtained by the reaction of beryllium powder and high-quality graphite powder.
7. Beryllium complexes
Since beryllium is an electron-deficient atom, its halide is a Lewis acid, and it is easy to form complexes or adducts with electron pair donors. Therefore beryllium can generate many complexes.
In 1923, American physical chemist Lewis put forward the acid-base electron theory that: all substances that can accept electron pairs are called acids, and all substances that can give electron pairs are called bases. Acids are electron docking acceptors and bases are electron pair donors.
Beryllium also forms many stable chelates. For example, evaporating beryllium hydroxide with acetic acid produces basic beryllium acetate Be4O(CH3COO)6. This is a covalent compound in which 4 Be atoms surround a central O atom and 6 acetate Ac- are arranged along the 6 edges of the tetrahedron. This complex is covalent and can be distilled for the purification of beryllium.
In other beryllium chelates, such as beryllium oxalate, naphthol complexes and acetylacetone complexes, in these chelates, beryllium atoms are surrounded by tetrahedra. Beryllium compounds are extremely toxic because of their extremely high solubility and their ease of complex formation.