Europium
[Xe] 4f⁷ 6s² · 2 · 8 · 18 · 25 · 8 · 2
The softest and most reactive lanthanide, and the world's best red phosphor. Europium is the only lanthanide with a stable +2 state, and the security of euro banknotes rests on the switch between +2 and +3.
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
- 63
- Atomic mass
- 151.964 а.е.м.
- Electron configuration
- [Xe] 4f⁷ 6s²
- Electrons per shell
- 2 · 8 · 18 · 25 · 8 · 2
- Block
- f-block
- Group
- no data
- Period
- 6
- Electronegativity (Pauling)
- 1.2
- Electronegativity (Allen)
- 1.01
- Atomic radius
- 233 pm
- Covalent radius
- 198 pm
- Van der Waals radius
- 233 pm
- Ionisation energy 1
- 547.1 kJ/mol
- Ionisation energy 2
- 1 085 kJ/mol
- Ionisation energy 3
- 2 404 kJ/mol
- Ionisation energy 4
- 4 120 kJ/mol
- Electron affinity
- 50 kJ/mol
- Common oxidation states
- +2, +3
- Oxidation states
- +2, +3
Physical properties
- State at 25 °C
- solid
- Density
- 5.264 g/cm³
- Melting point
- 1 099 K · 825.9 °C
- Boiling point
- 1 802 K · 1 528.9 °C
- Speed of sound
- no data
Thermal properties
- Heat of fusion
- 9.21 kJ/mol
- Heat of vaporisation
- 176 kJ/mol
- Specific heat capacity
- 0.182 J/(g·K)
- Thermal conductivity
- 13.9 W/(m·K)
Mechanical properties
- Young's modulus
- 18.2 GPa
- Shear modulus
- 7.9 GPa
- Bulk modulus
- 8.3 GPa
- Poisson ratio
- 0.15
- Mohs hardness
- no data
- Brinell hardness
- 167 MPa
Electrical and magnetic properties
- Electrical resistivity
- 900 nΩ·m
- Magnetic ordering
- paramagnetic
- Curie point
- no data
- Néel point
- no data
- Superconducting point
- no data
Crystal structure
- Crystal structure
- body-centred cubic (bcc)
- Lattice constants
- a = 458.1 pm
Abundance
- In the crust
- 2 mg/kg
- In the ocean
- 1.3·10⁻⁷ mg/L
- In the universe
- 0.05 mg/kg
- In the human body
- 0 mg/kg
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 151Eu | 47.81 % | 4.595·10⁹ Gyr | α |
| 153Eu | 52.19 % | stable | — |
Europium-151 is formally radioactive with a 5·10¹⁸-year alpha half-life — the decay was only detected in 2007.
Discovery
- Year of discovery
- 1901
- Discovered by
- Eugène-Anatole Demarçay
- Where
- France
- Origin of the name
- named after Europe
History
Eugène Demarçay isolated europium in 1901 from samarium samples after noticing spectral lines belonging to no known element. It was named after the continent.
Where it occurs
2 mg/kg of the crust — one of the rarest lanthanides. Its anomalous depletion or enrichment in a rock, the europium anomaly, is an important geochemical marker.
How it is produced
Separation is easier than for its neighbours because europium is readily reduced to +2 and precipitated as the sulfate, leaving the rest behind.
Role in living things
No biological role.
Safety
Of low toxicity. The metal oxidises readily and ignites in air.
Uses
- Red phosphor in picture tubes, fluorescent lamps and white LEDs
- Security marks on euro banknotes: under ultraviolet they glow red and green
- Reactor control rods
- Medical immunoassays using long-lived europium labels
Curiosities
- The glow of a euro banknote under ultraviolet is europium complexes at work.
- The europium anomaly in lunar rocks helped reconstruct the Moon's magma ocean.
- Europium is the only lanthanide soft enough to cut with a knife.
- The red of every colour television in the second half of the twentieth century came from europium.