40 Fun Facts About Germanium

Germanium expands as it freezes solid, a rare quirk it shares with which everyday liquid?

Water is the best-known member of this small club, which is why ice floats. Silicon and bismuth also swell as they solidify, while most molten materials shrink.

Germanium's discoverer first wanted which name, honoring a planet found by mathematical prediction?

Neptunium was his first pick, because Neptune had also been predicted before anyone saw it. The name was already claimed for another supposed element, so he honored his homeland instead.

The first working transistor was built in 1947 on a slab of germanium at which American lab?

Bell Labs researchers John Bardeen and Walter Brattain got it working in December 1947. For the next decade, transistor electronics ran almost entirely on germanium before silicon took over.

Germanium lenses look like solid gray metal, yet they are transparent to which kind of radiation?

Infrared light passes straight through germanium even though visible light cannot. That makes it the standard lens material for thermal cameras and night-vision gear.

Germanium honors Germany; which element did Marie Curie name after her own homeland?

Polonium was named for Poland in 1898, when the country was partitioned between three empires and missing from the map. Germanium had been named for its discoverer's homeland twelve years earlier.

Unlike scarce germanium, the silicon that replaced it in electronics comes from which raw material?

Sand and quartz supply all the silicon anyone could want, so only factory capacity limits it. In 1998 germanium cost almost $800 a kilogram, against under $10 for silicon.

Germanium crystals chilled almost to absolute zero help scientists hunt for which cosmic substance?

Dark matter particles, if they exist, should very occasionally bump into a germanium nucleus. The CDMS experiment watched discs of the element for the faint vibration and charge such a hit would leave.

The 1954 Regency TR-1 put four germanium transistors into the first commercial transistor what?

Radio shrank to pocket size in the TR-1, which went on sale in November 1954. Its makers expected Americans who were building bomb shelters to want one for emergencies.

Germanium and silicon both belong to a periodic table group named after which element at its top?

Carbon heads group 14, with silicon and germanium directly beneath it. Every member has four outer electrons, which is why germanium's chemistry echoes that of its lighter relatives.

Which chemist predicted germanium long before its discovery, calling the missing element ekasilicon?

Dmitri Mendeleev left a gap below silicon in his periodic table and forecast the missing element's weight, density and oxide. The real thing matched so closely that it helped convince chemists the table worked.

Long mistaken for a poorly conducting metal, germanium is now known as which kind of material?

Semiconductor behavior, switching between blocking and carrying current, made germanium the material of the first transistors. Before 1945 the world produced only a few hundred kilograms of it a year.

Germanium atoms stack in the same crystal pattern as silicon and which prized gemstone?

Diamond gives the pattern its name, the diamond cubic structure. Squeeze germanium hard enough, though, and it abandons that arrangement and turns into a true metal.

Germanium wafers form the base of which power source on the Mars rovers Spirit and Opportunity?

Solar cells for spacecraft are grown in three stacked layers on a germanium wafer, each layer tuned to a different slice of sunlight. The design is costly, so on Earth plain silicon panels still win.

Which notorious poison, element number 33, sits immediately after germanium in the periodic table?

Arsenic follows germanium, and the two are paired on purpose: a trace of it added to a germanium crystal supplies the spare electrons that let current flow.

In 1958 Jack Kilby used a sliver of germanium to build the first working example of which invention?

The integrated circuit was born on germanium because Kilby, newly hired at Texas Instruments, had no summer vacation and kept working while colleagues were away. Every microchip since descends from it.

Germanium transistors of the 1950s were built to replace which bulky, power-hungry components?

Vacuum tubes ran hot, broke easily and drained batteries. A transistor did the same job at a fraction of the size and power, with no filament to warm up.

Germanium dioxide is added to the core of which kind of telecommunications cable?

Optical fiber needs a core that bends light a little more than the glass around it, and a dash of germanium dioxide does the job. It replaced a titanium additive whose extra heat treatment left fibers brittle.

Germanium supplements once sold as health tonics were linked to serious damage in which organs?

The kidneys failed in several long-term users of germanium salts sold as cure-alls, and some of those users died. No medical evidence shows the supplements ever helped anyone.

Which country has long refined most of the world's germanium, about two-thirds of the total in 2011?

China produced about 80 of the 118 tonnes made worldwide in 2011. Russia and the United States, by comparison, managed only 5 and 3 tonnes that year.

Germanium is rarely mined for itself; most is recovered as a by-product of which metal's ores?

Zinc ore, the mineral sphalerite, can hold up to 0.3% germanium, enough to be worth pulling out once the main metal is gone. In 2007 recycling met about a third of world demand.

Which metal, named for France, melts in your hand and sits one place before germanium?

Gallium was found in 1875, eleven years before germanium, and both had been predicted from gaps in the periodic table. Its discoverer named it for Gaul, the old Roman name for France.

Germanium, silicon, boron and tellurium are all usually placed in which class of elements?

Metalloids sit between the metals and the nonmetals: germanium has a metallic shine but is brittle and conducts poorly. Only six elements are commonly given the label.

Germanium's first major use was in World War II diodes that detected the pulses of which technology?

Radar receivers needed crystal diodes of extremely pure germanium, and the wartime push to make them led directly to the transistor a few years later.

The germanium transistor of 1947 earned Bardeen, Brattain and Shockley which honor in 1956?

The Nobel Prize in Physics went to all three for discovering the transistor effect. Bardeen won it again in 1972 for explaining superconductivity, and remains the only person to take that prize twice.

Germanium can be recovered from the fly ash of power stations that burn which fuel?

Coal seams can be naturally enriched in germanium, and the richest ash ever tested held 1.6% of the element. The geochemist Victor Goldschmidt spotted the effect while surveying for deposits.

Germane, a gas made of germanium and hydrogen, has been detected in the atmosphere of which planet?

Jupiter carries traces of germane in its hydrogen-rich atmosphere. Germanium has also been spotted in the light of some of the most distant stars ever studied.

Which 1966 guitar pedal, made famous by Jimi Hendrix, was first built with germanium transistors?

Fuzz Face pedals built with germanium transistors drift with temperature and sound worse as they warm up. Later versions switched to cheaper, more consistent silicon.

High-purity germanium gamma-ray detectors work only when cooled to the temperature of which coolant?

Liquid nitrogen, at 77 kelvin, quiets the crystal's own electrons so that only a gamma ray can trigger a signal. Detectors like these are used to identify radiation sources at airport security.

Germane (GeH4), a toxic germanium gas used in chip-making, has the same shape as which fuel gas?

Methane, CH4, has the same four-cornered tetrahedral shape, with germanium simply taking the central atom's place. Germane is far nastier, irritating the eyes, skin and lungs.

Which Freiberg chemist discovered germanium in 1886 while analyzing a newly found mineral?

Clemens Winkler spent months separating the new element from a mineral sent over from a nearby mine, isolating it on February 6, 1886. He later worked through half a tonne of ore to study it properly.

The first transistor pressed two contacts cut from which metal's foil against a germanium crystal?

Gold foil was wrapped over the point of a plastic triangle and then sliced through at the tip, leaving two contacts a hair's width apart. A spring held them against the germanium.

Which metal sits directly below germanium in the periodic table, with lead beneath it in turn?

Tin has a gray form that looks more like germanium than like a metal and conducts electricity poorly. The two are neighbors in group 14, the column that runs down through silicon.

The germanium alloy GST flips between glassy and crystalline states to store data on which discs?

Rewritable DVDs record by heating tiny spots of the alloy so that they set either glassy or crystalline, and the change can be undone again and again. The same trick drives phase-change computer memory.

Germanium's placeholder name, ekasilicon, used a prefix meaning 'one' from which ancient language?

Sanskrit supplied eka, 'one', because the unknown element lay one place below silicon. An element two places below a known one got the prefix dvi instead.

Which US computer company pioneered silicon-germanium chips, now common in wireless devices?

IBM researcher Bernie Meyerson showed the alloy could be grown at low temperatures without defects, overturning what engineers had believed. Its chips outrun plain silicon yet use the same factories.

Bottles made with a germanium dioxide catalyst are prized for their clarity in which Asian country?

Japan favors the germanium catalyst because it gives polyester drinks bottles a higher brilliance. In the United States, by contrast, bottle makers do not use germanium at all.

Germanium is forged by slow neutron capture inside which kind of pulsating, aging star?

Red giants build germanium through the s-process, in which lighter elements gradually soak up neutrons. The 's' simply stands for slow.

Germanium was first isolated from which rare mineral, dug from a mine near Freiberg in the 1880s?

Argyrodite is an uncommon iron-black mineral with a purplish tinge. Similar crystals had turned up in Bolivia decades earlier, but they were misidentified and nobody realized what they held.

Bismuth germanate, a germanium compound that flashes under gamma rays, is used in which medical machines?

PET scanners ring the patient with such crystals to catch the gamma rays given off when positrons meet electrons. Bismuth germanate is the most common oxide-based scintillator.

Germanium was discovered at the mining university in Freiberg, a town in which German state?

Saxony was still a kingdom when germanium's discoverer was born in Freiberg in 1838. The mineral that held the element came from the Himmelsfürst mine in the nearby Ore Mountains.