Atomic number 32

Germanium

Ge
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Shells Orbitals 3d 4s 4p

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32 electrons in 4 shells: 2, 8, 18, 4.

Shells are a teaching model: an electron does not travel on a ring at a fixed distance.

Category: Metalloid
Period: 4
Group: 14
Block: p
Standard atomic weight: 72.630(8) Da
Electron configuration: [Ar] 3d¹⁰ 4s² 4p²
Phase at 25 °C: solid
Melting point: 938.25 °C
Boiling point: 2833 °C
Density: 5.323 g/cm³
Electronegativity (Pauling): 2.01
Discovered: 1886, Clemens Winkler

Neighbours in the table

Ga As

Germanium had a name and a place in the table fifteen years before anyone held a sample. Los Alamos records that Mendeleev predicted it in 1871 as ekasilicon, and Winkler found it in 1886. Germanium’s shells run 2, 8, 18 and 4, which accounts for 32 electrons and is written [Ar] 3d¹⁰ 4s² 4p². A main-group atom’s valence electrons are those in its highest shell, so germanium has four, the 4s and 4p pairs. Carbon and silicon above it have four as well; OpenStax ties a group’s likeness to that shared count and calls germanium’s chemistry very similar to silicon’s.

In the solid, each atom shares electrons with four neighbours at the corners of a regular tetrahedron, the pattern of diamond. A single crystal is therefore one enormous covalent molecule. Melting it means breaking those strong bonds, which is why germanium stays solid until 938.25 °C.

Metallic character grows down group 14 as the outer electrons become easier to remove. Carbon is a nonmetal, tin and lead are metals, and silicon and germanium sit between them as metalloids. Germanium looks metallic but conducts less well than a metal. Its electrons are bound more tightly to their nuclei than a metal’s, OpenStax explains, and a small energy gap separates a filled band of electron states from an empty one.

Where it is found

PubChem’s record gives 1.5 milligrams in a kilogram of crust and 5 × 10⁻⁵ milligrams in a litre of seawater. Los Alamos names two minerals that carry it, argyrodite and germanite, the second holding 8 per cent of the element. The US Geological Survey links the known resources to sulfide ores of zinc, lead and copper, and to lignite.

Los Alamos says the element is obtained commercially from the dust of smelters that treat zinc ore and from by-products of burning certain coals. In 2024 some of the germanium-bearing zinc concentrates from a mine in Alaska went to a refinery in Canada, which recovered their germanium as the dioxide and the tetrachloride. Los Alamos describes distilling the volatile tetrachloride in fractions to part germanium from other metals. Further refining leaves semiconductor-grade crystal with one part of impurity in 10¹⁰.

China led the world in producing and exporting germanium metal in 2024, the survey reports. Rich deposits were being worked or developed in Russia, Congo (Kinshasa), China and the United States. Much of the metal cut away while infrared optics are machined is recycled as new scrap.

Why it matters

The US Geological Survey ranks American uses, largest first, as fibre optics, infrared optics, semiconductors with solar cells, and radiation detectors. Los Alamos and Jefferson Lab call semiconductors its largest use. Fibre makers consume germanium dioxide and tetrachloride in the glass of data and telephone networks. Germanium and its oxide are transparent to infrared light, and the metal is shaped into infrared lenses. Its wafers underlie layered solar cells for spacecraft.

Jefferson Lab’s text in PubChem’s record says germanium doped with a little arsenic, gallium, indium, antimony or phosphorus is made into transistors. In a crystal of four-electron atoms, an arsenic atom brings a fifth electron. It finds no room in the filled band, so it enters the empty band as a negative carrier, giving an n-type crystal. An acceptor with three electrons leaves positive holes instead and makes the crystal p-type.

In August 2023 China set up export licensing for germanium, and in December 2024 it banned all exports to the United States. The survey’s average European price for metal of at least 99.999 per cent purity rose from 1,392 dollars a kilogram in 2023 to an estimated 2,100 in 2024. Silicon or gallium arsenide can replace it in some electronics, and other glasses in some infrared optics.

Properties

Properties of germanium Standard atomic weights from IUPAC/CIAAW (abridged, 2024); other values from PubChem's periodic table, kelvin converted to °C.
Property	Value	Unit	Source
Atomic number	32
Standard atomic weight	72.630(8) Da	Da	IUPAC/CIAAW 2024
Melting point	938.25 °C	°C	Los Alamos: 938.25 °C
Boiling point	2833 °C	°C	Los Alamos: 2833 °C
Density	5.323 g/cm³	g/cm³
Electronegativity (Pauling)	2.01
Electron configuration	1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p²
Phase at 25 °C	solid

Safety

Most of the reports to the European Chemicals Agency gathered on PubChem, 58.3 per cent, find no hazard in germanium. The aggregated classification still carries the signal word Danger, for a flammable solid, suspected harm to fertility or the unborn child, and organ damage from prolonged or repeated exposure. Haz-Map rates its systemic toxicity as comparatively low, while listing injury to the kidneys, liver and nerves, and nerve damage in people taking high-dose germanium supplements. The Hazardous Substances Data Bank places the fire hazard in the dust, and the PubChem Laboratory Chemical Safety Summary is the sheet to consult.

Questions

Is germanium a metal or a nonmetal?

Neither: it is a metalloid. OpenStax describes the metalloids, germanium among them, as metallic in appearance but poorer conductors than metals, and places their chemistry between that of metals and nonmetals. Germanium is a semiconductor: a small gap separates its filled band of electron energies from an empty one. Its crystal is held together by covalent bonds, as a nonmetal's would be. Yet it resembles the metals in rarely forming monatomic anions, negative ions made of a single atom.

How did Mendeleev predict germanium?

Jefferson Lab's text in PubChem's record says Mendeleev proposed the element in 1871 from gaps in the periodic table he had just drawn up; Los Alamos gives his name for it, ekasilicon. Fifteen years later Clemens Winkler found it in argyrodite, a silver mineral. CIAAW, IUPAC's atomic-weights commission, writes its formula as GeS₂·4Ag₂S and Jefferson Lab as Ag₈GeS₆.

How many isotopes does germanium have?

Jefferson Lab's text in PubChem's record counts five stable isotopes, with germanium-74 the most common at about 36.5 per cent of natural atoms, by CIAAW's figure. The International Atomic Energy Agency's nuclear data in the same record disagree on one of them: they give germanium-76 a half-life of 1.88 × 10²¹ years, by double beta decay. Germanium-68 is radioactive, with a half-life of 271.05 days.

What is germanium used for besides electronics and optics?

Beyond optics and electronics, Los Alamos lists germanium as an alloying agent, a phosphor in fluorescent lamps and a catalyst. IUPAC's note in PubChem's record adds a medical job for germanium-68: it calibrates PET (positron emission tomography) scanners. The US Geological Survey also reports germanium compounds turned into a gas, germane, which some semiconductor and solar-cell factories consume.