The germanium It is a metalloid element that is represented by the chemical symbol Ge and that belongs to group 14 of the periodic table. It is found underneath silicon, and shares many of its physical and chemical properties with it; so much so that once its name was Ekasilicio, predicted by Dmitri Mendeleev himself.
Its current name was given by Clemens A. Winkler, in honor of his homeland Germany. Hence, germanium is linked to this country, and that it is the first image that evokes to the mind those who do not know it too much..
Germanium, like silicon, consists of covalent crystals of three-dimensional tetrahedral lattices with Ge-Ge bonds. Likewise, it can be found in monocrystalline form, in which its grains are large, or polycrystalline, composed of hundreds of small crystals..
It is a semiconductor element at ambient pressure, but when it rises above 120 kbar it becomes a metallic allotrope; that is, possibly the Ge-Ge bonds are broken and their are arranged individually wrapped in the sea of their electrons.
It is considered a non-toxic element, as it can be handled without any type of protective clothing; although its inhalation and excessive intake can lead to the classic symptoms of irritation in individuals. Its vapor pressure is very low, so its smoke is unlikely to cause a fire.
However, inorganic (salts) and organic germaniums can be dangerous for the body, despite the fact that their Ge atoms interact in a mysterious way with biological matrices..
It is not really known if organic germanium can be considered a miracle cure for treating certain disorders as an alternative medicine. However, scientific studies do not support these claims, but reject them, and brand this element even as carcinogenic..
Germanium is not only a semiconductor, accompanying silicon, selenium, gallium and a whole series of elements in the world of semiconductor materials and their applications; It is also transparent to infrared radiation, making it useful for manufacturing heat detectors from different sources or regions..
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Germanium was one of the elements whose existence was predicted in 1869 by the Russian chemist Dmitri Mendeleev in his periodic table. He provisionally called it ekasilicon and placed it in a space on the periodic table between tin and silicon..
In 1886, Clemens A. Winkler discovered germanium in a mineral sample from a silver mine near Freiberg, Saxony. It was the mineral called argyrodite, due to its high silver content, and just discovered in 1885.
The argyrodite sample contained 73-75% silver, 17-18% sulfur, 0.2% mercury, and 6-7% a new element, which Winkler later named germanium..
Mendeleev had predicted that the density of the element to be discovered should be 5.5 g / cm3 and its atomic weight around 70. His predictions turned out to be quite close to those made by germanium.
In 1886, Winkler was able to isolate the new metal and found it similar to antimony, but he reconsidered and realized that the element he had discovered corresponded to ekasilicon..
Winkler named the element 'germanium' originated from the Latin word 'germania', a word they used to describe Germany. For this reason, Winkler named the new element germanium, after his native Germany..
In 1887, Winkler determined the chemical properties of germanium, finding an atomic weight of 72.32 by an analysis of pure germanium tetrachloride (GeCl4).
Meanwhile, Lecoq de Boisbaudran deduced an atomic weight of 72.3 by studying the element's spark spectrum. Winkler prepared several new compounds from germanium, including fluorides, chlorides, sulfides, and dioxides..
In the 1920s, investigations into the electrical properties of germanium led to the development of high-purity monocrystalline germanium.
This development allowed the use of germanium in diodes, rectifiers and microwave radar receivers during World War II..
The first industrial application came after the war in 1947, with the invention of germanium transistors by John Bardeen, Walter Brattain, and William Shockley, which were used in communications equipment, computers, and portable radios..
In 1954, high-purity silicon transistors began to displace germanium transistors due to the electronic advantages they possessed. And by the 1960s, germanium transistors had all but disappeared..
Germanium turned out to be a key component in the making of infrared (IR) lenses and windows. In the 1970s, silicon germanium (SiGe) voltaic cells (PVC) were produced that remain critical for satellite operations.
In the 1990s, the development and expansion of fiber optics increased the demand for germanium. The element is used to form the glass core of fiber optic cables.
Starting in 2000, high-efficiency PVCs and light-emitting diodes (LEDs) that use germanium led to an increase in the production and consumption of germanium..
Silvery white and shiny. When its solid is made up of many crystals (polycrystalline), it has a scaly or wrinkled surface, full of overtones and shadows. Sometimes it can even appear as grayish or black as silicon..
In standard conditions it is a semi-metallic element, brittle and metallic luster..
Germanium is a semiconductor, not very ductile. It has a high refractive index for visible light, but is transparent for infrared radiation, being used in equipment windows to detect and measure these radiation..
72.63 u
32
938.25 ºC
2,833 ºC
At room temperature: 5.323 g / cm3
At melting point (liquid): 5.60 g / cm3
Germanium, like silicon, gallium, bismuth, antimony, and water, expands as it solidifies. For this reason, its density is higher in the liquid state than in the solid state..
36.94 kJ / mol
334 kJ / mol
23.222 J / (mol K)
At a temperature of 1,644 K, its vapor pressure is only 1 Pa. This means that its liquid emits hardly any vapors at that temperature, so it does not imply a risk of inhalation..
2.01 on the Pauling scale
-First: 762 kJ / mol
-Second: 1,537 kJ / mol
-Third: 3,302.1 kJ / mol
60.2 W / (m K)
1 Ω · m at 20 ºC
3S cm-1
Diamagnetic
6.0 on the Mohs scale
Relatively stable. It is not affected by air at room temperature and oxidizes at temperatures above 600 ºC.
6 10-1 N / m at 1,673.1 K
It oxidizes at temperatures above 600 ° C to form germanium dioxide (GeOtwo). Germanium gives rise to two forms of oxides: germanium dioxide (GeOtwo) and germanium monoxide (GeO).
Germanium compounds generally exhibit the +4 oxidation state, although in many compounds germanium occurs with the +2 oxidation state. The oxidation state - 4 occurs, for example in magnesium germanide (MgtwoGe).
Germanium reacts with halogens to form tetrahalides: germanium tetrafluoride (GeF4), gaseous compound; germanium tetraiodide (GeI4), solid compound; germanium tetrachloride (GeCl4) and germanium tetrabromide (GeBr4), both liquid compounds.
Germanium is inert towards hydrochloric acid; but it is attacked by nitric acid and sulfuric acid. Although hydroxides in aqueous solution have little effect on germanium, it dissolves readily in molten hydroxides to form geronates..
Germanium has four valence electrons according to its electronic configuration:
[Ar] 3d10 4stwo 4ptwo
Like carbon and silicon, their Ge atoms hybridize their 4s and 4p orbitals to form four sp hybrid orbitals.3. With these orbitals they bond to satisfy the valence octet and, consequently, have the same number of electrons as the noble gas of the same period (krypton).
In this way, the Ge-Ge covalent bonds arise, and having four of them for each atom, surrounding tetrahedra are defined (with one Ge in the center and the others at the vertices). Thus, a three-dimensional network is established by the displacement of these tetrahedra along the covalent crystal; which behaves as if it were a huge molecule.
The covalent germanium crystal adopts the same face-centered cubic structure of diamond (and silicon). This allotrope is known as α-Ge. If the pressure increases to 120 kbar (about 118,000 atm), the crystal structure of α-Ge becomes body-centered tetragonal (BCT, for its acronym in English: Body-centered tetragonal).
These BCT crystals correspond to the second allotrope of germanium: β-Ge, where the Ge-Ge bonds are broken and arranged in isolation, as happens with metals. Thus, α-Ge is semi-metallic; while β-Ge is metallic.
Germanium can either lose its four valence electrons, or gain four more to become isoelectronic with krypton..
When it loses electrons in its compounds, it is said to have positive numbers or oxidation states, in which the existence of cations with the same charges as these numbers is assumed. Among these we have the +2 (Getwo+), the +3 (Ge3+) and the +4 (Ge4+).
For example, the following compounds have germanium with positive oxidation numbers: GeO (Getwo+ORtwo-), GeTe (Getwo+Teatwo-), GetwoCl6 (Getwo3+Cl6-), GeOtwo (Ge4+ORtwotwo-) and GeStwo (Ge4+Stwotwo-).
Whereas when it gains electrons in its compounds, it has negative oxidation numbers. Among them the most common is -4; that is, the existence of the anion Ge is assumed4-. In germanides this happens, and as examples of them we have the Li4Ge (Li4+Ge4-) and MgtwoGe (Mgtwotwo+Ge4-).
Germanium is a relatively rare element in the earth's crust. Few minerals contain an appreciable amount of it, among which we can mention: argyrodite (4AgtwoS · GeStwo), germanite (7CuS · FeS · GeStwo), briartite (CutwoFeGeS4), renierite and canfieldite.
They all have something in common: they are sulfur or sulfurous minerals. Therefore, germanium predominates in nature (or at least here on Earth), like GeStwo and not GeOtwo (in contrast to its counterpart SiOtwo, silica, widely spread).
In addition to the minerals mentioned above, germanium has also been found to be found in mass concentrations of 0.3% in coal deposits. Also, some microorganisms can process it to generate small amounts of GeHtwo(CH3)two and GeH3(CH3), which end up displaced towards rivers and seas.
Germanium is a by-product of the processing of metals such as zinc and copper. To obtain it, it must undergo a series of chemical reactions to reduce its sulfur to the corresponding metal; that is, take away the GeStwo its sulfur atoms so that it remains as Ge simply.
Sulfur minerals undergo a roasting process in which they are heated together with the air for oxidations to occur:
GeStwo + 3 Otwo → GeOtwo + 2 SOtwo
To separate the germanium from the residue, it is transformed into its respective chloride, which can be distilled:
Geotwo + 4 HCl → GeCl4 + 2 htwoOR
Geotwo + 2 Cltwo → GeCl4 + ORtwo
As can be seen, the transformation can be carried out using hydrochloric acid or chlorine gas. The GeCl4 then hydrolyzes back to GeOtwo, so it precipitates as a whitish solid. Finally, the oxide reacts with hydrogen to reduce to metallic germanium:
Geotwo + 2 htwo → Ge + 2 HtwoOR
Reduction that can also be done with charcoal:
Geotwo + C → Ge + COtwo
The germanium obtained consists of a powder that is molded or tamped into metal bars, from which radiant germanium crystals can be grown..
Germanium does not possess any isotope of great abundance in nature. Instead, it has five isotopes whose abundances are relatively low: 70Ge (20.52%), 72Ge (27.45%), 73Ge (7.76%), 74Ge (36.7%) and 76Ge (7.75%). Note that the atomic weight is 72.630 u, which averages all the atomic masses with the respective abundances of the isotopes.
Isotope 76Ge is actually radioactive; but its half-life is so great (t1/2= 1.78 × 10twenty-one years) which is practically among the five most stable isotopes of germanium. Other radioisotopes, such as 68Ge and 71Ge, both synthetic, have shorter half-lives (270.95 days and 11.3 days, respectively).
The environmental risks to germanium are somewhat controversial. Being a slightly heavy metal, a propagation of its ions from water-soluble salts could inflict damage on the ecosystem; that is, animals and plants can be affected by consuming Ge ions3+.
Elemental germanium is safe as long as it is not powdered. If it is in dust, a current of air can drag it to sources of heat or highly oxidizing substances; and consequently there is a risk of fire or explosion. Likewise, its crystals can end up in the lungs or eyes, causing severe irritations..
A person can safely handle a germanium disk in his office without worrying about any accident. However, the same cannot be said for its inorganic compounds; that is, its salts, oxides and hydrides. For example, the GeH4 or Germanic (analogous to CH4 and YesH4), it is a very irritating and flammable gas.
Now, there are organic sources of germanium; Among them, mention may be made of 2-carboxyethylgermasquioxane or germanium-132, an alternative supplement known to treat certain ailments; although with evidence cast in doubt.
Some of the medicinal effects attributed to germanium-132 is to strengthen the immune system, which is why it helps fight cancer, HIV and AIDS; regulates the functions of the body, as well as improves the degree of oxygenation in the blood, eliminates free radicals; and also cures arthritis, glaucoma and heart disease.
However, organic germanium has been linked to serious damage to the kidneys, liver and nervous system. That is why there is a latent risk when it comes to consuming this germanium supplement; Well, although there are those who consider it a miracle cure, there are others who warn that it does not offer any scientifically proven benefit.
Germanium is transparent to infrared radiation; that is, they can pass through it without being absorbed.
Thanks to this, germanium glasses and lenses have been built for infrared optical devices; for example, coupled with an IR detector for spectroscopic analysis, in lenses used in far-infrared space telescopes to study the most distant stars in the Universe, or in light and temperature sensors.
Infrared radiation is associated with molecular vibrations or heat sources; so the devices used in the military industry to view targets with night vision have components made with germanium.
Germanium as a semiconductor metalloid has been used to build transistors, electrical circuits, light-emitting diodes, and microchips. In the latter, germanium-silicon alloys, and even germanium, by itself have begun to replace silicon, so that smaller and more powerful circuits can be designed..
Its rust, GeOtwo, Due to its high refractive index, it is added to glasses so that they can be used in microscopy, wide-angle objectives and fiber optics..
Germanium has not only come to replace silicon in certain electronic applications, but it can also be coupled with gallium arsenide (GaAs). Thus, this metalloid is also present in solar panels.
The GeOtwo it has been used as a catalyst for polymerization reactions; for example, in the one necessary for the synthesis of polyethylene terephthalate, a plastic with which shiny bottles sold in Japan are made.
Likewise, the nanoparticles of their platinum alloys catalyze redox reactions where they involve the formation of hydrogen gas, making these voltaic cells more effective..
Finally, it has been mentioned that there are Ge-Si and Ge-Pt alloys. In addition to this, its Ge atoms can be added to the crystals of other metals, such as silver, gold, copper and beryllium. These alloys show greater ductility and chemical resistance than their individual metals..
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