Germanium (Ge)

The first transistor, built at Bell Labs in 1947, was germanium, not silicon — germanium was easier to purify at the time, and it took another decade for silicon to win on heat tolerance and on the quality of its oxide. It is transparent to infrared and opaque to visible light, so a germanium window looks like polished metal but a thermal camera sees straight through it. Mendeleev predicted it as eka-silicon in 1871 and Winkler's 1886 measurements matched the prediction closely enough to settle most remaining doubts about the periodic table.

Properties

Atomic number

32

Symbol

Ge

Standard atomic weight

72.63 u

Category

Metalloid

Group

14

Period

4

Block

p-block

Electron configuration

[Ar] 4s² 3d¹⁰ 4p²

Electrons per shell

2, 8, 18, 4

Melting point

1,211.4 K — 938.3 °C — 1720.9 °F

Boiling point

3,106 K — 2832.8 °C — 5131.1 °F

Density

5.323 g/cm³

Electronegativity

2.01 (Pauling)

Oxidation states

+4, +2

Discovered

1886 by Clemens Winkler

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p²

Noble gas shorthand

[Ar] 4s² 3d¹⁰ 4p²

Shells

K: 2 · L: 8 · M: 18 · N: 4

What it is used for

• Infrared lenses for thermal imaging and night vision
• Fibre-optic cable cores, where it raises the refractive index
• The catalyst for making PET plastic bottles
• Silicon-germanium chips in phone radios and high-speed circuits
• Space solar cells, as the substrate for multi-junction stacks

Neighbours in the table

Group 14

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Germanium sits in group 14 with carbon, silicon, tin, lead, flerovium.