Beryllium
Beryllium (chemical symbol Be) is an alkaline earth metallic element, that has no known function in any organism. Unfortunately beryllium is very poisonous, manifesting as chronic beryllium lung disease, which causes premature mortality in one third .
Chemistry
Basic chemistry
Beryllium is a naturally-occurring element in the alkaline earth metal group with the atomic number 4, and atomic weight of 9.0122. It is a very rare element on earth and is never found in its pure elemental state. It has a low density and is very strong.
Radiochemistry
All naturally-occurring beryllium is beryllium-9, which is the only stable isotope in nature. Small quantities of beryllium-10 (half life: 1.39 × 10 years) and beryllium-7 (half life: 53 days) are formed in the high atmosphere largely by cosmic ray mediated spallation of nitrogen and oxygen nuclei. These isotopes settle on the earth and their measurement can be used in geochronology .
Industrial applications
It has found an important niche role in industry due to its ideal combination of extreme lightness (one third less dense than aluminum), stiffness (six times as stiff as steel), and high heat resilience over a wide thermal spectrum. These unique properties means that it is used extensively in specialized products in the aerospace, automotive, energy, defense, medical and electronics industries .
Radiological applications
As the beryllium atom only has five neutrons, four protons, and four electrons, it is almost completely transparent to high-energy particles and ionizing radiation. Indeed a beryllium window is more transparent to x-rays than a normal glass one.
Therefore beryllium windows are employed to cover the ends of x-ray tubes from which the x-rays exit. Of course a window (of any material) is mandatory in tube construction to maintain vacuum.
Toxicity
Solid beryllium metal and beryllium alloys are benign, however its dust is highly toxic. Beryllium primarily exerts its deleterious effects on the lungs, producing beryllium lung disease, which has been recognized as a clinical entity since 1943 . The lung disease can be acute or chronic. Less commonly berylliosis involves the skin, the lymph nodes, and liver.
Beryllium has been implicated as a precipitant in metal fume fever, but this is contentious .
Beryllium is found throughout the natural environment, including in coal, wood, food, and gems, e.g. emeralds. Thus the populace in general are exposed to beryllium in their air, potable water and food.
Significant occupational exposure is now much rarer due to stringent safety standards.
History and etymology
Beryllium was discovered in 1798 by the French chemist Nicolas Louis Vauquelin (1763-1829), and he initially called it glucinium, as the salts of beryllium have a sweet taste, but renamed it beryllium due to its presence in the gemstone beryl . Interestingly he also discovered the metallic element chromium. However elemental beryllium was not isolated in its pure form until the 1820s by the German chemist Friedrich Wöhler (1800–1882) .
Siehe auch:
