Germanium
Element 32 · Metalloid
Germanium is a hard, lustrous, gray-white metalloid sitting directly below silicon in group 14. Its claim to fame is electronic: the first working transistor of 1947 was a germanium device, launching the semiconductor revolution before silicon took over for most chips.
Today germanium thrives in niches silicon cannot fill — it is transparent to infrared light, making it the lens material for thermal cameras, and its oxide strengthens fiber-optic glass. As a metalloid it shares traits of both metals and nonmetals, forming a diamond-like crystal structure.
Key facts
| Atomic number | 32 |
|---|---|
| Atomic weight | 72.630 |
| Category | Metalloid |
| Group / Period | 14 / 4 |
| Block | p |
| Electron configuration | [Ar] 3d10 4s2 4p2 |
| Common oxidation states | +4, +2 |
| State at STP | Solid |
| Electronegativity | 2.01 |
| Atomic radius | 125 pm |
| Density | 5.323 g/cm³ |
| Melting point | 938.25 °C |
| Boiling point | 2833 °C |
Occurrence
Germanium occurs in traces in zinc ores and coal, and in the rare mineral argyrodite from which it was isolated in 1886. Like Mendeleev's other predicted elements, it was found as eka-silicon with properties matching his forecast. It is recovered mainly from zinc smelter residues.
Applications
Fiber-optic communication systems use germanium dioxide in glass cores
Infrared lenses for night-vision cameras are made from germanium
High-efficiency multi-junction solar cells contain germanium layers
Polyester manufacturing uses germanium dioxide catalysts
Specialty transistors and gamma-ray detectors use pure germanium crystals
Common compounds
- germanium dioxide
- germanium tetrachloride
- germane
The first transistor ever built, in 1947, was made of germanium — not silicon.
Data source: IUPAC standard atomic weights 2021