Erbium (Er)

Every transoceanic fibre-optic cable depends on erbium. An erbium-doped fibre amplifier boosts a light signal directly, without converting it to electricity and back, and it happens to amplify at 1,550 nm — precisely the wavelength where silica fibre is most transparent. That coincidence, exploited from about 1990, is what made long-haul optical networking economic, and therefore what made the modern internet affordable.

Properties

Atomic number

68

Symbol

Er

Standard atomic weight

167.26 u

Category

Lanthanide

Period

6

Block

f-block

Electron configuration

[Xe] 6s² 4f¹²

Electrons per shell

2, 8, 18, 30, 8, 2

Melting point

1,802 K — 1528.8 °C — 2783.9 °F

Boiling point

3,141 K — 2867.8 °C — 5194.1 °F

Density

9.07 g/cm³

Electronegativity

1.24 (Pauling)

Oxidation states

+3

Discovered

1843 by Carl Gustaf Mosander

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹²

Noble gas shorthand

[Xe] 6s² 4f¹²

Shells

K: 2 · L: 8 · M: 18 · N: 30 · O: 8 · P: 2

What it is used for

• Erbium-doped fibre amplifiers, which carry the internet across oceans
• Er:YAG lasers for dermatology and dentistry
• Pink colouring in glass, glazes and cubic zirconia
• Neutron-absorbing burnable poison in reactor fuel

Neighbours in the table