Beryllium and Beryllium Compounds

Beryllium (atomic number, 4; relative atomic mass, 9.01) is a metal, which belongs to Group IIA of the Periodic Table. The oxidation state of beryllium compounds is +2. Selected chemical and physical properties of beryllium, beryllium– aluminium and beryllium–copper alloys, and various beryllium compounds can be found in the previous IARC Monograph (IARC, 1993). Beryllium is the lightest of all solid chemically stable substances, and has an unusually high melting-point. It has a very low density and a very high strength-to-weight ratio. Beryllium is lighter than aluminium but is greater than 40% more rigid than steel. It has excellent electrical and thermal conductivities. Its only markedly adverse feature is relatively pronounced brittleness, which restricts the use of metallic beryllium to specialized applications (WHO, 1990). Because of its low atomic number, beryllium is very permeable to X-rays. Neutron emission after bombardment with α or γ rays is the most important of its nuclear physical properties, and beryllium can be used as a neutron source. Moreover, its low neutron absorptiveness and high-scattering cross-section make it a suitable moderator and reflector in structural materials in nuclear facilities; where most other metals absorb neutrons emitted during the fission of nuclear fuel, beryllium atoms only reduce the energy of such neutrons, and reflect them back into the fission zone (Ballance et al., 1978; Newland, 1984; WHO, 1990). The chemical properties of beryllium differ considerably from those of the other alkaline earths, but it has several chemical properties in common with aluminium. Like aluminium, beryllium is amphoteric and shows very high affinity for oxygen; on exposure to air or water vapour, a thin film of beryllium oxide forms on