Germanium (Ge)
Germanium (symbol Ge) is the chemical element with atomic number 32: a metalloid, solid at 0 °C, with an atomic mass of 72.63 u. Discovered in 1886 (Clemens Winkler).
Germanium is a metalloid, an element halfway between a metal and a nonmetal. It was used to build the very first transistor in 1947 before silicon dethroned it. Today it hides in optical fibers and in the lenses of thermal cameras, because it lets infrared light through.
Key facts
- Atomic number
- 32
- Symbol
- Ge
- French name
- Germanium
- Atomic mass
- 72.63 u
- Molar mass
- 72.63 g/mol
- Family
- Metalloids
- Position
- period 4, group 14, p-block
- State at 0 °C
- Solid
- Melting point
- 938.3 °C
- Boiling point
- 2,832.9 °C
- Density
- 5.32 g/cm³
- Electronegativity (Pauling)
- 2.01
- First ionization energy
- 762 kJ/mol
- Atomic radius
- 125 pm
- Electron configuration
- [Ar] 3d¹⁰ 4s² 4p²
- Abundance in Earth's crust
- 1.5 ppm (55th most abundant element)
- Indicative price
- 1,000 $/kg (order of magnitude)
- Radioactive
- no
- Discovery
- 1886, Clemens Winkler
Origin of the name
From the Latin Germania, Germany.
What does germanium look like?
A shiny, grayish-white solid that looks metallic, hard but brittle as glass. It is opaque to visible light yet transparent to infrared.
Where is germanium found?
At about 1.5 ppm of Earth's crust, germanium is rare and widely scattered. It is recovered mainly from zinc ores and from certain coal ashes, which concentrate it naturally.
Natural sources
- Argyrodite
- Germanite
- Renierite
- Sphalerite (traces)
How is germanium produced?
It is extracted as a by-product of zinc refining or from the fly ash of coal-fired power plants, then purified as germanium tetrachloride before being reduced to metal. World output is about 100 to 150 tonnes a year, dominated by China, which also restricted its exports in 2023.
Top producers
- China
- Russia
- Canada
- United States
What is germanium used for?
- Doping the core of optical fibers (germanium oxide).
- Lenses and windows for infrared and night-vision cameras.
- Substrates for multijunction space solar cells.
- Catalyst for making some PET plastics.
- Ultra-precise gamma-ray detectors.
In everyday life
- Fiber-optic internet
- Thermal camera
- Some PET plastic bottles
- Vintage “fuzz” guitar pedals
Role in living things
Germanium has no known biological role. Dietary supplements touting “organic germanium” have caused serious, even fatal, kidney damage with no proven benefit.
Hazards of germanium
The metal and its oxides have low toxicity, but some compounds, such as germane (GeH₄), a gas used in microelectronics, are toxic and flammable.
Cosmic origin
- Supernovae: Forged in the cores of massive stars, then scattered when they explode.
- Dying stars: Made slowly in red giants (stars like the Sun at the end of their lives).
History of germanium
In 1871 Mendeleev predicted an “eka-silicon.” In 1886, German chemist Clemens Winkler isolated it from argyrodite, a silver ore from Freiberg in Saxony. Its properties matched the predictions so spectacularly that it helped win acceptance for the periodic table. Winkler named it after Germany (Germania).
Did you know?
- The first transistor, built at Bell Labs in December 1947, was a slab of germanium.
- Winkler reportedly first considered the name “neptunium,” but it had already been claimed for another discovery (which turned out to be false).
- Like water, gallium and bismuth, germanium expands when it solidifies.
Isotopes of germanium
Four stable isotopes, plus a fifth, germanium-76, so feebly radioactive that it lasts more than a billion trillion years. Physicists hunt it for a “neutrinoless” decay.
- germanium-68: radioactive, half-life 271 days. Parent in the generator that supplies hospitals with gallium-68.
- germanium-70: 20.57% of natural germanium, stable
- germanium-72: 27.45% of natural germanium, stable
- germanium-73: 7.75% of natural germanium, stable
- germanium-74: 36.5% of natural germanium, stable
- germanium-76: 7.73% of natural germanium, radioactive, half-life 2.02 × 10²¹ years. Studied for double beta decay to uncover the true nature of the neutrino.
Related elements
Same family (metalloids): Boron (B), Silicon (Si), Arsenic (As), Antimony (Sb), Tellurium (Te).
Same column (group 14): Carbon (C), Silicon (Si), Tin (Sn), Lead (Pb), Flerovium (Fl).