Germanium - chemistry.

Germanium - chemistry. Germanium, symbol Ge, hard, brittle, grayish-white, crystalline semimetallic element. The atomic number of germanium is 32; it is in group 14 (or IVa) of the periodic table (see Periodic Law). The Russian chemist Dmitry Mendeleyev predicted the existence and chemical properties of germanium in 1871; because of its position under silicon in the periodic table, he called it ekasilicon. The element was actually discovered in the silver-sulfide ore argyrodite by the German chemist Clemens Alexander Winkler in 1886. Germanium was named after the country of Germany, where it was discovered. Germanium is in the same chemical family as carbon, silicon, tin, and lead, and resembles these elements in forming organic derivatives such as tetraethyl germanium and tetraphenyl germanium. Germanium forms hydrides--germanomethane, or germane (GeH4); germanoethane (Ge2H6); and germanopropane (Ge3H8)--analogous to those formed by carbon in the methane series (see Chemistry, Organic). The most important compounds of germanium are the oxide GeO2 (germanic acid) and the halides. Germanium is separated from other metals by distillation of the tetrachloride. Germanium ranks 54th in order of abundance of the elements in Earth's crust. Germanium melts at about 938°C (about 1720°F), boils at about 2833°C (about 5131°F), and has a specific gravity of 5.3; its atomic weight is 72.6. Germanium occurs in small quantities in the ores of silver, copper, and zinc, and in the mineral germanite, which contains 8 percent germanium. Germanium and its compounds are used in a variety of ways. Suitably prepared germanium crystals have the property of rectifying, or passing electrical currents in one direction only, and so were used extensively during and after World War II (1939-1945) as detectors for ultra-high-frequency radio and radar signals. Germanium crystals also have other specialized electronic uses. Germanium was the first metal used in the transistor, the electronic device that requires far less current than the vacuum tube. Germanium oxide is used in the manufacture of optical glass and as a drug in the treatment of pernicious anemia. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.