198 | The History and Use of Our Earth’s Chemical Elements (FDA) withdrew its approval for their use. Congressional hearings with manufacturers in
198 | The History and Use of Our Earth’s Chemical Elements (FDA) withdrew its approval for their use. Congressional hearings with manufacturers in
2005 produced new information that has reversed the FDA’s ban on their use—but only with certain manufacturers of implants. The debate continues.
GERMANIUM SYMBOL:Ge PERIOD:4 GROUP:14(IVA) ATOMICNO:32
ATOMICMASS:72.61amu VALENCE:2and4 OXIDATIONSTATE:+2and+4 NATU- RALSTATE:Solid ORIGINOFNAME: Germanium’snamewasderivedfromtheLatinwordGermania,mean- ing“Germany.” ISOTOPES:Thereareatotalof38isotopesofGermanium,fiveofwhicharestable.The stableisotopesofgermaniumandtheirnaturalabundanceareasfollows:Ge-70= 20.37%,Ge-72=27.31%,Ge-73=7.76%,Ge-74=36.73%,andGe-76=7.83%. Ge-76isconsideredstablebecauseithassuchalonghalf-life(0.8×10 +25 years)Allthe other33isotopesareradioactiveandareproducedartificially.
ELECTRONCONFIGURATION EnergyLevels/Shells/Electrons Orbitals/Electrons
s2,p6
3-M=18
s2,p6,d10
4-N=4
s2,p2
Properties Germanium has a gray shine with a metallic silvery-white luster. It is a brittle element
classed as a semimetal or metalloid, meaning it is neither a metal such as iron or copper nor
a nonmetal, such as phosphorus, sulfur, or oxygen. Germanium has some properties like
a metal and some like a nonmetal. It is a crystal in its pure state, somewhat like silicon. It will combine with oxygen to form germanium dioxide, which is similar to silicon dioxide (sand).
Germanium is not found in its free elemental state because it is much too reactive. For the most part, it is found combined with oxygen, either as germanium monoxide or as germanium dioxide. Also, it is recovered from the ores of zinc, copper, and arsenic and the flue deposits of burning coal.
The crystal structure of germanium is similar to that of diamonds and silicon, and its semi- conducting properties are also similar to silicon. The melting point of germanium is 938.3°C, its boiling point is 2833°C, and its density is 5.323 g/cm 3 .
199 Characteristics
Guide to the Elements |
Once germanium is recovered and formed into blocks, it is further refined by the manufac- turer of semiconductors. It is melted, and the small amounts of impurities such as arsenic, gal- lium, or antimony, are added. They act as either electron donors or acceptors that are infused (doped) into the mix. Then small amounts of the molten material are removed and used to grow crystals of germanium that are formed into semiconducting transistors on a germanium chip. The device can now carry variable amounts of electricity because it can act as both an insulator and a conductor of electrons, which is the basis of modern computers.
AbundanceandSource Germanium, the 52nd most abundant element in the Earth’s crust, is widely distributed,
but never found in its natural elemental state. It is always combined with other elements, particularly oxygen.
Germanium’s main minerals are germanite, argyrodite, renierite and canfieldite, all of which are rare. Small amounts of germanium are found in zinc ore, as well as in copper and arsenic ores. It is known to concentrate in certain plants on Earth, particularly in coal: com- mercial quantities are collected from the soot in the stacks where coal is burned.
History In 1871 Dmitri Mendeleev predicted the existence of a new element that would have simi-
lar properties as silicon. He called this yet to be found element “eka-silicon,” which he assigned the symbol “Es” with an atomic weight of 72 and a specific gravity of 5.5.
When Clemens Alexander Winkler (1838–1904) was analyzing silver ore (Ag 8 GeS 6 ), he came up short on the resulting products by 7%. He kept working on this problem, and in 1886 he found the missing 7% as a newly identified element that he then named germanium after his native country, Germany.
In 1948 William Bradford Shockley (1910–1989), who is considered the inventor of the transistor, and his associates at Bell Research Laboratories, Walter Houser Brattain (1902–1987) and John Bardeen (1908–1991), discovered that a crystal of germanium could act as a semi- conductor of electricity. This unique property of germanium indicated to them that it could be used as both a rectifier and an amplifier to replace the old glass vacuum tubes in radios. Their friend John Robinson Pierce (1910–2002) gave this new solid-state device the name transistor, since the device had to overcome some resistance when a current of electricity passed through it. Shockley, Brattain, and Bardeen all shared the 1956 Nobel Prize in Physics.
CommonUses By far, the most common use for germanium is in the semiconductor and electronics
industries. As a semiconductor, germanium can be used to make transistors, diodes, and numerous types of computer chips. It was the first element that could be designed to act as different types of semiconductors for a variety of applications just by adding variable amounts of impurities (doping) to the germanium crystals.
Germanium is also used as a brazing alloy, for producing infrared transmitting glass and other types of lenses, and for producing synthetic garnets (semiprecious gemstones) that have special magnetic properties.