32 Ge 72.63

Germanium

Metalloid Germanium solid

[Ar] 3d¹⁰ 4s² 4p² · 2 · 8 · 18 · 4

← Ga Gallium As Arsenic →

The semiconductor the first transistor was made from, later displaced by silicon. Mendeleev predicted germanium as eka-silicon, and its discovery in 1886 was the third confirmation of the periodic law in a row.

3D model

Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.

Drag to rotate, scroll to zoom

Atomic properties

Atomic number: 32
Atomic mass: 72.63 а.е.м.
Electron configuration: [Ar] 3d¹⁰ 4s² 4p²
Electrons per shell: 2 · 8 · 18 · 4
Block: p-block
Group: Carbon group
Period: 4
Electronegativity (Pauling): 2.01
Electronegativity (Allen): 1.99
Atomic radius: 125 pm
Covalent radius: 120 pm
Van der Waals radius: 211 pm
Ionisation energy 1: 762 kJ/mol
Ionisation energy 2: 1 537.5 kJ/mol
Ionisation energy 3: 3 302.1 kJ/mol
Ionisation energy 4: 4 411 kJ/mol
Ionisation energy 5: 9 020 kJ/mol
Electron affinity: 119 kJ/mol
Common oxidation states: +4
Oxidation states: -4, -3, -2, -1, +1, +2, +3, +4

Physical properties

State at 25 °C: solid
Density: 5.323 g/cm³
Melting point: 1 211.4 K · 938.3 °C
Boiling point: 3 106 K · 2 832.9 °C
Speed of sound: 5 400 m/s

Thermal properties

Heat of fusion: 36.94 kJ/mol
Heat of vaporisation: 334 kJ/mol
Specific heat capacity: 0.32 J/(g·K)
Thermal conductivity: 60.2 W/(m·K)

Mechanical properties

Young's modulus: 103 GPa
Shear modulus: 41 GPa
Bulk modulus: 75 GPa
Poisson ratio: 0.26
Mohs hardness: 6
Brinell hardness: no data

Electrical and magnetic properties

Electrical resistivity: 5·10⁸ nΩ·m
Magnetic ordering: diamagnetic
Curie point: no data
Néel point: no data
Superconducting point: no data

Crystal structure

Crystal structure: diamond cubic
Lattice constants: a = 565.75 pm

Abundance

In the crust: 1.5 mg/kg
In the ocean: 5·10⁻⁵ mg/L
In the universe: 0.2 mg/kg
In the human body: no data

Isotopes

Isotope	Abundance	Half-life	Decay mode
⁷⁰Ge	20.52 %	stable	—
⁷²Ge	27.45 %	stable	—
⁷³Ge	7.76 %	stable	—
⁷⁴Ge	36.52 %	stable	—
⁷⁶Ge	7.75 %	stable	—

Germanium-76 undergoes extremely rare double beta decay; detectors of enriched ⁷⁶Ge hunt for the neutrinoless version, a key to the nature of the neutrino.

Discovery

Year of discovery: 1886
Discovered by: Clemens Winkler
Where: Germany
Origin of the name: from Germania, the Latin name for Germany

History

Clemens Winkler found the element in argyrodite from a Saxon mine and named it for Germany. The match with the predicted eka-silicon was so exact that the periodic law was left without sceptics.

Where it occurs

1.5 mg/kg of the crust — rare and dispersed. It is recovered from zinc concentrates and from the ash of certain coals.

How it is produced

Via germanium tetrachloride, repeatedly distilled and hydrolysed. Zone refining brings it to semiconductor purity.

Role in living things

No biological role. Organic germanium compounds were once sold as supplements, but the claims did not hold up and some of them damage the kidneys.

Safety

Germanium itself is of low toxicity. The hydride GeH₄ is dangerous, as is prolonged consumption of germanium dioxide supplements.

Uses

Infrared optics: lenses for thermal imagers and night vision
Optical fibre — germanium raises the refractive index of the core
Silicon–germanium heterostructures in high-frequency electronics
A catalyst in PET plastic production

Curiosities

The first transistor ever built, at Bell Labs in 1947, was germanium.
Germanium is transparent to infrared and completely opaque to visible light.
Mendeleev's eka-silicon: predicted density 5.5, actual 5.32.
Germanium is one of the few elements whose liquid is denser than its solid, as water is.