|Name , symbol , atomic number||Germanium, Ge, 32|
|Group , period , block||14 , 4 , p|
|Mass fraction of the earth's envelope||5.6 ppm|
|Atomic mass||72,630 (8) u|
|Atomic radius (calculated)||125 (125) pm|
|Covalent radius||122 pm|
|Van der Waals radius||211 pm|
|Electron configuration||[ Ar ] 3 d 10 4 s 2 4 p 2|
|1. Ionization energy||7th.899 435 (12) eV ≈ 762.18 kJ / mol|
|2. Ionization energy||15th.934 610 results (25 eV) ≈ 1 537.46 kJ / mol|
|3. Ionization energy||34.0576 (12) eV ≈ 3 286.1 kJ / mol|
|4. Ionization energy||45.7155 (12) eV ≈ 4 410.9 kJ / mol|
|5. Ionization energy||90.500 (19) eV ≈ 8 732 kJ / mol|
|Crystal structure||Diamond structure|
|density||5.323 g / cm 3 (20 ° C )|
|magnetism||diamagnetic ( Χ m = −7.1 10 −5 )|
|Melting point||1211.4 K (938.3 ° C)|
|boiling point||3106 K (2830 ° C)|
|Molar volume||13.63 · 10 −6 m 3 · mol −1|
|Heat of evaporation||330 kJ / mol|
|Heat of fusion||31.8 kJ mol −1|
|Speed of sound||5400 m s −1 at 293.15 K.|
|Specific heat capacity||308.3 J kg −1 K −1|
|Work function||5.0 eV|
|Electric conductivity||( Intrinsic conduction ) 2 A · V −1 · m −1 at 300 K.|
|Thermal conductivity||60 W m −1 K −1|
|Oxidation states||−4, 2, 4|
|Normal potential||0.247 V (Ge 2+ + 2 e - → Ge)|
|Electronegativity||2.01 ( Pauling scale )|
|For other isotopes see list of isotopes|
As far as possible and customary, SI units are used.
Unless otherwise noted, the data given apply to standard conditions .
Germanium (from Latin Germania ' Germany ', after the country in which it was first found) is a chemical element with the element symbol Ge and the atomic number 32. In the periodic table it is in the 4th period and in the 4th main group (14th . IUPAC group , p- block and carbon group ). It was first detected in the mineral argyrodite in 1886 .
When Dmitri Mendeleev designed the periodic table in 1871 , he came across a gap below silicon and postulated a previously unknown element, which he called eka-silicon. Mendeleev made predictions about the properties of eka-silicon and its compounds, but these were rejected by science.
In 1885, Clemens Winkler (1838–1904), a chemist at the Bergakademie Freiberg , found, when he was working with the newly discovered mineral argyrodite, that its quantitative analysis always yielded a shortfall of around seven percent. As often as the analysis was repeated, the shortfall remained more or less constant and Winkler finally suspected that the mineral contained a previously unknown element. After four months of work, he finally managed to isolate a white sulphide precipitate on February 6, 1886 , which could be reduced to a metallic powder in a stream of hydrogen . Based on the previously discovered planet Neptune , Winkler initially wanted to name the new element Neptunium . However, since this name had already been used for another suspected element, he named it germanium after the place of discovery. Winkler initially suspected that the germanium was the eka stibium postulated by Mendeleev , while Mendeleev initially wanted to classify it as eka cadmium rather than eka silicon. After further properties were determined, it was confirmed that it was probably the predicted element eka-silicon. Mendeleev had derived its properties from his periodic table, so this discovery contributed to the recognition of the periodic table:
|Specific weight of the dioxide||4.7||4.703|
|Molecular volume of the dioxide||22nd||22.16|
|Boiling point of the tetrachloride||below 100 ° C||86 ° C|
|Specific weight of the tetrachloride||1.9||1.87|
|Molecular volume of the tetrachloride||113||113.35|
The origin and etymology of the name germanium could also result from a semantic misunderstanding in connection with its predecessor element gallium , because there are two theories for the naming of gallium. After the first, the French chemist Paul Émile Lecoq de Boisbaudran named the element after Gaul , the Latin name of his native France . The second gives the Latin word gallus (cock) as the source of the name, which in French means le coq ("the cock"). Paul Émile Lecoq de Boisbaudran would have named the new element after his own name. Winkler assumed that the previous element gallium was named after the nationality of the French discoverer. He named the new chemical element “germanium” in honor of his country (Latin Germania for Germany).
Germanium is widespread, but only occurs in very low concentrations. The Clarke value , i.e. the average content in the earth's crust, is around 1.5 g / t . In nature it occurs mostly in the form of sulfides or thiogermanates and is often found as a companion in copper and zinc ores , including in the Mansfeld copper shale . The most important minerals are argyrodite (Ag 8 GeS 6 ), canfieldite , germanite (Cu 6 FeGe 2 S 8 ) and renierite . Some plants enrich germanium. This property leads to highly controversial theses regarding the physiology of plants (“plant defense against viruses”), with which applications in homeopathy are justified.
Extraction and manufacture
According to the USGS , annual production in 2014 was an estimated 165 t, 120 t of which in China. The price for 1 kg of germanium was around 1,900 USD in 2014 . According to the EU, the price was USD 300 per kg in 2003 and rose to USD 1,000 by 2009.
The germanium oxide (GeO 2 ) -containing flue gases from zinc ore processing are particularly suitable for producing germanium. The germanium is enriched from the flue gas by dissolving the flue dust in sulfuric acid. After the dissolved GeO 2 and ZnO have been precipitated, further processing is carried out by distilling the metal chlorides. The hydrolysis then leads back to the oxide, which is reduced to germanium with hydrogen. The representation of high purity germanium can, for. B. be done by the zone melting process.
Germanium is in the semimetallic series in the periodic table , but according to the more recent definition it is classified as a semiconductor . Elemental germanium is very brittle and very stable in air at room temperature. It is only oxidized to germanium (IV) oxide (GeO 2 ) when it is heavily glowing in an oxygen atmosphere . GeO 2 is dimorphic and is converted from the rutile modification (CN = 6) to the β-quartz structure (CN = 4) at 1033 ° C. In powder form, it can be easily ignited and continues to burn after removing the ignition source. In compact form, it is not flammable.
Germanium is bivalent and tetravalent. Germanium (IV) compounds are the most persistent. Germanium is not attacked by hydrochloric acid , potassium hydroxide solution and dilute sulfuric acid . In alkaline hydrogen peroxide solutions, concentrated hot sulfuric acid and concentrated nitric acid , on the other hand, it is dissolved with the formation of germanium dioxide hydrate. According to its position in the periodic table , its chemical properties are somewhere between silicon and tin .
Germanium wafers are significantly more fragile than silicon wafers.
As a semiconductor , germanium in single crystal form was the leading material in electronics in the middle of the 20th century, especially for the manufacture of the first diodes and bipolar transistors available on the market , until it was replaced by silicon in these areas. Applications are found today in high-frequency technology (e.g. as silicon-germanium compound semiconductors) and detector technology (e.g. as X-ray detectors). For solar cells made of gallium arsenide (GaAs), wafers made of germanium are sometimes used as the carrier material. The lattice constant of germanium is very similar to that of gallium arsenide, so that GaAs can grow epitaxially on germanium single crystals.
Glasses and fibers
Its second main application is in infrared optics in the form of windows and lens systems made of poly- or monocrystalline germanium as well as optical glasses with infrared permeability, so-called chalcogenide glasses. Areas of application for this include military and civil night vision devices and thermal imaging cameras .
Other essential uses are in the production of optical waveguides and polyester fibers: In modern glass fibers for telecommunications, germanium tetrachloride is used to generate an enrichment of germanium dioxide in the inner fiber core during chemical vapor deposition . This results in a higher refractive index in the core compared to the fiber cladding , which ensures that the light waves are guided. In polyester chemistry, germanium dioxide is used as a catalyst in the production of certain polyester fibers and granulates, especially for recyclable PET bottles (PET = polyethylene terephthalate ).
Nuclear medicine and nuclear engineering
As a high-purity single crystal , germanium is used as a radiation detector.
Germanium in food supplements
The substance bis (carboxyethyl) germanium sesquioxide ( Ge-132 ) has been touted as a dietary supplement for use in a number of diseases including cancer , chronic fatigue syndrome , immune deficiency , AIDS , high blood pressure , arthritis and food allergies . So far, no positive effects on the course of the disease have been scientifically proven.
According to the European Directive 2002/46 / EC on the approximation of the laws of the Member States on food supplements , germanium should not be used in food supplements. In many EU countries that have already aligned their national legislation, including Germany and Austria, the addition of germanium as a mineral source in food supplements is therefore not allowed.
The responsible authorities expressly warn against the consumption of Ge-132 , as serious damage to health and death cannot be ruled out.
Medicinal use of germanium
A therapeutic efficacy of the anti- neoplastic substance Spirogermanium in cancer diseases has not been proven. There are no approved finished medicinal products with the active ingredient spirogermanium. In Germany, medicinal products (recipes) containing germanium, apart from homeopathic dilutions from D4, are considered questionable. Their production and their distribution are therefore prohibited. Germanium metallicum is available in the form of homeopathic medicines . Di- potassium germanium citrate lactate is described as a component of homeopathic preparations .
Germanium and its compounds have a relatively low acute toxicity . Traces of germanium can be found in the following foods: beans , tomato juice , oysters , tuna and garlic . According to the current state of science, it is not an essential trace element. There is no known biological function for germanium. No germanium deficiency diseases are known.
Health damage caused by germanium occurred several times in humans after prolonged intake of germanium compounds as a dietary supplement. This leads to functional disorders of the kidneys up to (irreversible) kidney failure, which can be fatal for the patient . Peripheral neuropathy and other secondary neurological damage have also been reported.
It is known from animal experiments that germanium has a low acute oral toxicity. In rats, the LD 50 value (the dose at which half of the test animals die) is 3700 mg per kilogram of body weight.
The mechanism of toxicity of germanium is not yet fully understood. However, specific pathological effects on the mitochondria of different cells were observed.
It is also discussed whether germanium might interact with silicon in bone metabolism. It can block the action of diuretics and reduce or block the activity of a number of enzymes , such as dehydrogenases . In animal experiments , mice show an increased hexabarbital-induced sleep duration when they were additionally treated with germanium compounds. This suggests that cytochrome P450 activity is also restricted. There have been reports of organic germanium compounds that block the detoxification enzyme glutathione-S-transferase .
Bioavailability and metabolism
Germanium is very easily absorbed by the body when ingested. It is distributed over the entire body tissue, primarily in the kidneys and the thyroid . In contrast to inorganic germanium compounds, organogermanics do not accumulate in the human body. However, there are only a few studies of germanium metabolism.
Germanium forms Ge (II) - u. more stable Ge (IV) compounds, only a few are of technical importance.
Of the germanium halides, Ge (II) - u. Ge (IV) representative known. Germanium tetrachloride , (GeCl 4 ), a liquid with a boiling point of 83 ° C, forms when germanium oxides are exposed to hydrogen chloride and is an important intermediate product in the production of germanium. Highly pure GeCl 4 is used in the manufacture of optical waveguides made of quartz glass in order to produce a high-purity germanium (IV) oxide layer on the inside of the quartz fibers. The disproportionation of germanium (II) iodide with the formation of germanium and germanium (IV) iodide can also be used to produce highly pure germanium layers :
Germanates are compounds of germanium that are derived from its oxide. The germanium is present as germanate in almost all minerals containing germanium.
Germans are the name given to the hydrogen compounds of germanium, which form a homologous series of chain molecules of different lengths. Monogerman or germanium hydride (GeH 4 ) is a gas and is used in the semiconductor industry for epitaxy and doping.
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