Matter & Energy

Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.


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.

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 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; germanoethane; and germanopropane—analogous to those formed by carbon in the methane series. The most important compounds of germanium are the oxide (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 the earth's crust. Germanium melts at about 937° C (about 1719° F), boils at about 2830° C (about 5126° F), and has a specific gravity of 5.3; its atomic weight is 72.59.

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.