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Jai Ganesh

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Germanium

Germanium

Gist

Germanium is a chemical element with the symbol Ge and atomic number 32. It's a lustrous, grayish-white metalloid that exhibits properties of both metals and nonmetals. Found in Group 14 of the periodic table, between silicon and tin, it shares many chemical and physical similarities with silicon.

Germanium is classified as a metalloid, meaning it exhibits properties of both metals and nonmetals. While it has a metallic appearance and can conduct electricity under certain conditions, it's not a true metal. It's found in the same group as silicon and tin in the periodic table and shares some of their properties.

Germanium normalizes many physiological functions, particularly blood characteristics including pH, glucose, minerals, cholesterol, uric acid, hemoglobin and leukocytes. Conversely, germanium deficiency can result in numerous diseases, primarily oncogenic conditions.

Summary

Germanium is a chemical element; it has symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid or a nonmetal in the carbon group that is chemically similar to silicon. Like silicon, germanium naturally reacts and forms complexes with oxygen in nature.

Because it seldom appears in high concentration, germanium was found comparatively late in the discovery of the elements. Germanium ranks 50th in abundance of the elements in the Earth's crust. In 1869, Dmitri Mendeleev predicted its existence and some of its properties from its position on his periodic table, and called the element ekasilicon. On February 6, 1886, Clemens Winkler at Freiberg University found the new element, along with silver and sulfur, in the mineral argyrodite. Winkler named the element after Germany, his country of birth. Germanium is mined primarily from sphalerite (the primary ore of zinc), though germanium is also recovered commercially from silver, lead, and copper ores.

Elemental germanium is used as a semiconductor in transistors and various other electronic devices. Historically, the first decade of semiconductor electronics was based entirely on germanium. Presently, the major end uses are fibre-optic systems, infrared optics, solar cell applications, and light-emitting diodes (LEDs). Germanium compounds are also used for polymerization catalysts and have most recently found use in the production of nanowires. This element forms a large number of organogermanium compounds, such as tetraethylgermanium, useful in organometallic chemistry.

Germanium is not thought to be an essential element for any living organism. Similar to silicon and aluminium, naturally-occurring germanium compounds tend to be insoluble in water and thus have little oral toxicity. However, synthetic soluble germanium salts are nephrotoxic, and synthetic chemically reactive germanium compounds with halogens and hydrogen are irritants and toxins.

Details

Germanium (Ge) is a chemical element between silicon and tin in Group 14 (IVa) of the periodic table, a silvery-gray metalloid, intermediate in properties between the metals and the nonmetals. Although germanium was not discovered until 1886 by Clemens Winkler, a German chemist, its existence, properties, and position in the periodic system had been predicted in 1871 by the Russian chemist Dmitry Ivanovich Mendeleyev, who called the hypothetical element ekasilicon. (The name germanium derives from the Latin word Germania [Germany] and was given to the element by Winkler.) Germanium did not become economically significant until after 1945, when its properties as a semiconductor were recognized as being of value in electronics. Many other substances now also are used as semiconductors, but germanium remains of primary importance in the manufacture of transistors and of components for devices such as rectifiers and photocells.

On a weight basis, germanium is a scarce but not an extremely rare (about 1.5 parts per million) element in the crust of the Earth, equaling in abundance beryllium, molybdenum, and cesium and exceeding the elements math, cadmium, antimony, and mercury. In the cosmos the atomic abundance of germanium is 50.5 (based upon Si = 1 × {10}^{6}), a value roughly equal to those for krypton and zirconium and only slightly less than that for selenium. The cosmic abundance is much less than those of a number of the heavier elements; e.g., bromine, strontium, tin, barium, mercury, and lead. All of the elements of lower nuclear charge than germanium, except beryllium, boron, scandium, and gallium, are cosmically more abundant than germanium. Cosmically, germanium is believed to be one of the many elements formed by neutron absorption after the initial processes of hydrogen and helium burning and alpha-particle absorption.

Germanium is widely distributed in nature but is too reactive to occur free. Primary minerals include argyrodite (from which it was first isolated), germanite, renierite, and canfieldite, all of them rare; only germanite and renierite have been used as commercial sources for the element. Trace quantities of germanium are found in certain zinc blendes, in sulfidic ores of copper and math, and in coals, the latter possibly a consequence of the concentration of the element by plants of the Carboniferous Period in geologic history. Certain present-day plants are known to concentrate germanium. Both zinc-process concentrates and ash and flue dusts from coal-burning installations provide commercial sources of germanium.

In refining germanium, the low-grade residues obtained from its ores are treated with strong hydrochloric acid, and the resulting germanium tetrachloride is distilled, purified by repeated redistillation, and hydrolyzed to form germanium dioxide, which is then reduced by hydrogen to a powdery form of the metal that is melted at a temperature of about 1,100° C (2,000° F [in an inert atmosphere]) and cast into ingots or billets.

The element is brittle rather than ductile; the atoms in its crystals are arranged as are the carbon atoms in diamond. The electrical and semiconducting characteristics of germanium are comparable to those of silicon. It is not attacked by air at room temperature but is oxidized at 600°–700° C (1,100°–1,300° F) and reacts quickly with the halogens to form tetrahalides. Among the acids, only concentrated nitric or sulfuric acid or aqua regia (a mixture of nitric and hydrochloric acids) attack germanium appreciably. Although aqueous caustic solutions produce little effect on it, germanium dissolves rapidly in molten sodium hydroxide or potassium hydroxide, thereby forming the respective germanates.

Germanium forms stable oxidation states of +2 and +4, the compounds of the latter being more stable and numerous. The two most important compounds of germanium are the dioxide (GeO2) and the tetrachloride (GeCl4). Germanates, formed by heating the dioxide with basic oxides, include zinc germanate (Zn2GeO4), used as a phosphor (a substance that emits light when energized by radiation). The tetrachloride, already mentioned as an intermediate in obtaining germanium from its natural sources, is a volatile, colorless liquid that freezes at about -50° C (-58° F) and boils at 84° C (183.2° F).

For use in electronic devices, germanium ingots or billets require further purification, which usually is effected by the technique of zone refining. Finally, single crystals are generated from the melt at carefully controlled temperatures, using a seed crystal as a nucleus. Single crystals of germanium are grown in an atmosphere of nitrogen or helium from the molten material. These are then transformed into semiconductors by being doped (infused) with electron donor or acceptor atoms, either by incorporating the impurities in the melt during growth of the crystal or by diffusing the impurities into the crystal after it has been formed.

Germanium compounds in which germanium is in the +2 oxidation state are well characterized as solids, and in general they are readily oxidized. Elemental germanium can be electrodeposited from many solutions and melts of its compounds. It is of interest that as little as one milligram of dissolved germanium per litre seriously interferes with the electrodeposition of zinc.

In addition to its applications in electronic devices, germanium is used as a component of alloys and in phosphors for fluorescent lamps. Because germanium is transparent to infrared radiation, it is employed in equipment used for detecting and measuring such radiation, such as windows and lenses. The high index of refraction of germanium dioxide renders it valuable as a component of glasses used in optical devices, such as wide-angle lenses for cameras and microscope objectives. The toxicology of germanium and its compounds is poorly defined.

The five stable isotopes of germanium occur in the following relative amounts: germanium-70, 20.5 percent; germanium-72, 27.4 percent; germanium-73, 7.8 percent; germanium-74, 36.5 percent; and germanium-76, 7.8 percent. Nine radioactive isotopes have been reported.

Element Properties

atomic number  :  32
atomic weight  :  72.63
melting point  :  937.4° C (1,719.3° F)
boiling point  :  2,830° C (5,130° F)
density  :  5.323 g/{cm}^{3}.
oxidation states  :  +2, +4.

Additional Information:

Appearance

A silvery-white semi-metal. It is brittle.

Uses

Germanium is a semiconductor. The pure element was commonly doped with math, gallium or other elements and used as a transistor in thousands of electronic applications. Today, however, other semiconductors have replaced it.

Germanium oxide has a high index of refraction and dispersion. This makes it suitable for use in wide-angle camera lenses and objective lenses for microscopes. This is now the major use for this element.

Germanium is also used as an alloying agent (adding 1% germanium to silver stops it from tarnishing), in fluorescent lamps and as a catalyst.

Both germanium and germanium oxide are transparent to infrared radiation and so are used in infrared spectroscopes.

Biological role

Germanium has no known biological role. The element is non-toxic. Certain germanium compounds have low toxicity in mammals, while being effective against some bacteria. This has led some scientists to study their potential use in pharmaceuticals.

Natural abundance

Germanium ores are very rare. They are found in small quantities as the minerals germanite and argyrodite.

Germanium minerals are also present in zinc ores, and commercial production of germanium is carried out by processing zinc smelter flue dust. It can also be recovered from the by-products of combustion of certain coals.

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