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Beryllium is a chemical element; it has symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to form minerals. Gemstones high in beryllium include beryl (aquamarine, emerald, red beryl) and chrysoberyl.
Unlike the oxides formed by the other Group 2 elements (alkaline earth metals), beryllium oxide is amphoteric rather than basic. Beryllium oxide formed at high temperatures (>800 °C) is inert, but dissolves easily in hot aqueous ammonium bifluoride (NH 4 HF 2) or a solution of hot concentrated sulfuric acid (H 2 SO 4) and ammonium sulfate ((NH ...
The reaction with lithium hydride (in which the hydride ion is the Lewis base), forms sequentially LiBeH 3 and Li 2 BeH 4. [3] The latter contains the tetrahydridoberyllate(2-) anion BeH 2− 4. Beryllium hydride reacts with trimethylamine, N(CH 3) 3 to form a dimeric adduct with bridging hydrides. [11]
Many mixed ligand complexes are simply formed by addition of Lewis bases to diaryl and dialkylberyllium compounds. Many derivatives are known of the type BeR 2 L 2 and BAr 2 L 2 are known where L = thioether, pyridine, NHC, [14] and 1,4-Diazabutadienes. [15] Beryllium forms a variety of complexes with N-hetereocyclic carbenes (NHCs). [16] [17] [18]
Beryllium fluoride has distinctive optical properties. In the form of fluoroberyllate glass, it has the lowest refractive index for a solid at room temperature of 1.275. Its dispersive power is the lowest for a solid at 0.0093, and the nonlinear coefficient is also the lowest at 2 × 10 −14.
(Note that the beryllium scale is inverted, so increases on this scale indicate lower beryllium-10 levels). Beryllium-10 has a half-life of 1.39 × 10 6 y, and decays by beta decay to stable boron-10 with a maximum energy of 556.2 keV. [7] [8] It is formed in the Earth's atmosphere mainly by cosmic ray spallation of nitrogen and oxygen.
The γ form is produced by cooling a melt of SrF 2 and Be 2 and the β form is made by precipitating from a water solution. When melted and heated to 850–1145 °C, Be 2 gas evaporates leaving behind molten SrF 2. [11] The barium tetrafluoroberyllate is very insoluble and can be used for gravimetric analysis of beryllium. [11]
With acids, beryllium salts are formed. [12] For example, with sulfuric acid, H 2 SO 4, beryllium sulfate is formed: Be(OH) 2 + H 2 SO 4 → BeSO 4 + 2 H 2 O. Beryllium hydroxide dehydrates at 400 °C to form the soluble white powder, beryllium oxide: [12] Be(OH) 2 → BeO + H 2 O. Further heating at higher temperature produces acid insoluble ...