Europium (Eu)

Europium gave colour television a usable red: before europium-doped phosphors arrived in the 1960s, the red channel was so dim that the whole picture had to be run darker to match it. The euro banknote carries europium compounds that glow specific colours under ultraviolet, which is one of the checks a cash machine makes. It is the softest and least dense lanthanide, and the most reactive — a fresh surface tarnishes in seconds and the metal has to be kept under oil.

Properties

Atomic number

63

Symbol

Eu

Standard atomic weight

151.96 u

Category

Lanthanide

Period

6

Block

f-block

Electron configuration

[Xe] 6s² 4f⁷

Electrons per shell

2, 8, 18, 25, 8, 2

Melting point

1,095 K — 821.9 °C — 1511.3 °F

Boiling point

1,802 K — 1528.8 °C — 2783.9 °F

Density

5.24 g/cm³

Oxidation states

+3, +2

Discovered

1901 by Eugène-Anatole Demarçay

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f⁷

Noble gas shorthand

[Xe] 6s² 4f⁷

Shells

K: 2 · L: 8 · M: 18 · N: 25 · O: 8 · P: 2

What it is used for

• The red phosphor in colour televisions, LED lamps and fluorescent tubes
• Anti-counterfeiting marks in euro banknotes
• Neutron absorbers in reactor control rods
• Blue-emitting phosphors in white LEDs

No Pauling electronegativity is listed in the standard tables for europium; scales that estimate one put it near 1.2.

Neighbours in the table