Germanium

germanium (Latin: Germanium) is a chemical element with atomic number 32, and symbol Ge belonging to period 4 of the table periodic period of the elements.

It is a greyish-white, shiny, hard, and brittle metalloid in the carbon group, chemically similar to its neighboring group, silicon and tin. Pure germanium is a semiconductor with an appearance similar to elemental silicon. Like silicon, germanium naturally reacts and complexes with oxygen in nature.

Because it rarely occurs in high concentration, germanium was discovered relatively late in the history of chemistry. Germanium ranks near fiftieth in relative abundance of the elements in the Earth's crust. In 1869, Dmitri Mendeleev predicted its existence and some of its properties from its position in his periodic table, and named the element ekasilicon. Nearly two decades later, in 1886, Clemens Winkler found the new element, along with silver and sulfur, in a rare mineral called argyrodite. Although the new element somewhat resembled arsenic and antimony in appearance, the combination ratios in the compounds matched Mendeleev's predictions for a relative of silicon. Winkler named the element after his country, Germany. Today, germanium is mined primarily from sphalerite (the primary zinc ore), although germanium is also recovered commercially from silver, lead, and copper ores.

Elemental germanium is used as a semiconductor in transistors and other electronic devices. Historically, the first decade of semiconductor electronics was based entirely on germanium. Currently, the main end uses are fiber optic systems, infrared optics, solar cell applications, and light-emitting diodes (LEDs). Germanium compounds are also used for polymerization catalysts and have 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 considered a critical element for technology.

Germanium is not thought to be an essential element for any living organism. Some complex organic germanium compounds are being investigated as possible pharmaceuticals, although none have been successful so far. Like silicon and aluminum, naturally occurring germanium compounds tend to be insoluble in water and therefore have little oral toxicity. However, synthetic soluble germanium salts are nephrotoxic, and synthetic germanium compounds chemically reactive with halogens and hydrogen are irritating and toxic.

Main features

Pure Germanium

It is a brittle, lustrous grayish-white semimetal that retains its luster at ordinary temperatures. It has the same crystalline structure as diamond and is resistant to acids and alkalis.

It forms a large number of organometallic compounds and is an important semiconductor material used in transistors and photodetectors. Unlike most semiconductors, germanium has a small band gap (band gap) so it responds effectively to infrared radiation and can be used in low current amplifiers.

Applications

The applications of germanium are limited by its high cost and in many cases its substitution by cheaper materials is being investigated.

• Optical fiber.
• Electronics: radars and amplifiers of electric guitars used to recreate sounds of the first time of rock and roll; alloys of Germanato de Silicio (SiGe) in integrated high-speed circuits. Si/Ge sandwich compounds are also used to increase electron mobility in silicon (streched silicon).
• Infrared optical, in the form of metal, as it is opaque in the area of visible light, but transparent in the infrared, between 2 and 25 micrometers. Spectroscopes, night vision systems and other equipment.
• Lens, with high refractive index, wide angle and microscopes.
• The Au alloy is used with 12% germanium.
• As a hardening element of aluminum, magnesium and tin.
• Chemotherapy.
• Germain tetrachloride is a Lewis acid and is used as a catalyst in polymer synthesis (PET). Currently, this is its main use.

History

Prediction of germanium, "?=70" (periodic table 1869)

The properties of germanium (from the Latin Germania, Germany) were predicted in 1871 by Mendeleyev based on its position in the periodic table, an element he called eka-silicon. The German Clemens Winkler demonstrated the existence of this element in 1886, a discovery that served to confirm the validity of the periodic table, given the similarities between the predicted and observed properties:

In mid-1885, a new mineral was discovered in a mine near Freiberg, Saxony, which was named argyrodite because of its high silver content. Chemist Clemens Winkler analyzed this new mineral, which turned out to be a combination of silver, sulfur and a new element. Winkler was able to isolate the new element in 1886 and found it to be similar to antimony. He initially considered the new element to be eka-antimony, but was soon convinced that it was eka-silicon.] Before Winkler published his results on the new element, he decided that he would name his element neptunium, since the recent discovery of the planet Neptune in 1846 had been similarly preceded by mathematical predictions of its existence. Like the existence of the new element, the existence of the planet Neptune had been predicted towards 1843 by the two mathematicians John Couch Adams and Urbain Le Verrier, using the calculation methods of celestial mechanics. They did this to try to explain the fact that the planet Uranus, when observed very closely, appeared to be dragged slightly out of position in the sky. However, the name "neptunium" it had already been given to another proposed chemical element, although not to the element that today bears the name of neptunium that was discovered in 1940. R. Hermann published in 1877 his discovery of a new element below tantalum in the periodic table, to which named neptunium, after the Greek god of the oceans and seas. Winkler then named the new element germanium instead, from the Latin word, Germania, for Germany, after his native land. [10] Argyrodite was empirically shown to be Ag₈GeS₆. Because this new element showed some similarities to the elements arsenic and antimony, its proper place on the periodic table was being considered, but its similarities to the element "ekasilicon" predicted by Dmitri Mendeleev confirmed that place in the periodic table. Using more than 500 kg of ore material from the mines of Saxony, Winkler confirmed the new element's chemical properties in 1887. He also determined an atomic weight of 72, 32 by analysis of pure germanium tetrachloride (GeCl
4), while Lecoq de Boisbaudran deduced 72, 3 by comparison of the lines in the element's spark spectrum.

Winkler was able to prepare several new germanium compounds, including fluorides chlorides sulfides dioxide and tetraethylgermanium (Ge(C₂H₅)₄), the first Germanic organo. The physical data for these compounds, which corresponded well with Mendeleev's predictions, made the discovery an important confirmation of Mendeleev's idea about the periodicity of the elements. Here is a comparison between the prediction and Winkler's data:

Abundance and obtaining

Sample of germanium.

It is obtained from deposits of silver, zinc and copper. The only profitable ores for germanium extraction are germanite (69% Ge) and garnierite (7-8% Ge); it is also present in coal, argyrodite and other minerals. The largest amount, in the form of oxide (GeO₂), is obtained as a by-product of obtaining zinc or coal combustion processes (in Russia and China the process is under development).

The purification of germanium goes through its tetrachloride that can be distilled and then reduced to the element with hydrogen or with elemental magnesium.

With a purity of 99.99%, for electronic uses it is obtained by refining through zone melting, resulting in 25 to 35 mm crystals used in transistors and diodes; with this technique impurities can be reduced to 0.0001 ppm.

Germanium was discovered to be a semiconductor in 1926, but it could not be used in practice until 1942, when it was obtained at a competitive price. The development of germanium transistors from 1947 opened the door to numerous electronic applications that are commonplace today. Between 1950 and the early 1970s, electronics accounted for the bulk of the growing demand for germanium until it began to be replaced by silicon due to its much lower cost. Currently, most of the consumption goes to fiber optics (about half), night vision equipment and catalysis in the polymerization of plastics, although their replacement by cheaper catalysts is being investigated. In the future, it is possible that the electronic applications of silicon-germanium alloys will be extended in substitution of gallium arsenide, especially in wireless telecommunications.

In addition, its bactericidal properties are being investigated since its toxicity to mammals is low.

Isotopes

Germanium has five stable isotopes, the most abundant being Ge-74 (35.94%). Eighteen germanium radioisotopes have been characterized, with Ge-68 having the longest half-life at 270.8 days. In addition, 9 metastable states are known.

Precautions

Some germanium compounds (germanium tetrahydride or germano) have some toxicity in mammals but are lethal to some bacteria. It is also lethal for taenia.

Toxicity

Germanium is most commonly found in nature as a contaminant of various minerals and is obtained from the cadmium residues remaining from the processing of zinc ores. Toxicological investigations have shown that germanium does not localize to any tissue since it is rapidly excreted mainly in the urine. Excessive doses of germanium damage the capillary beds of the lungs. It produces a very marked diarrhea that causes dehydration, hemoconcentration, drop in blood pressure and hypothermia.