Europium
Europium is a chemical element with symbol Eu and atomic number 63. It was isolated in 1901 and is named after the continent of Europe. It is a moderately hard, silvery metal which readily oxidizes in air and water.
Identity
- Atomic mass
- 151.964 u
- Category
- Lanthanides
- Group
- 3
- Period
- 6
- Block
- f
- Oxidation States
- +2, +3
- Phase (25 °C)
- Solid
Electronic Structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f7
- Short configuration
- [Xe] 4f7 6s2
- Electrons per shell
- 2, 8, 18, 25, 8, 2
- Electronegativity (Pauling)
- 1.20
- Electron affinity
- 11.2 kJ/mol
- 1st ionization energy
- 547 kJ/mol
- Ionization energies
- 547 · 1085 · 2404 · 4120 kJ/mol
Physical properties
- Melting point
- 825.9 °C (1099 K)
- Boiling point
- 1528.8 °C (1802 K)
- Density
- 5.264 g/cm³
- Molar heat capacity
- 27.7 J/(mol·K)
Chemical behavior of europium
Europium has seven outer electrons ([Xe] 4f⁷ 6s²) and is the most singular lanthanide: alongside the usual +3 it presents a very stable +2 due to its half-filled 4f shell. Its electronegativity is low (1.20) and it is the most reactive of the series, soft as lead. Its Eu²⁺ (blue) and Eu³⁺ (red) ions emit the light that tints screens and LEDs.
Reactivity
4 Eu + 3 O₂ → 2 Eu₂O₃
It oxidizes extremely rapidly in air, even at room temperature, becoming covered with oxide. It must be stored in mineral oil or an inert atmosphere.
2 Eu + 6 H₂O → 2 Eu(OH)₃ + 3 H₂
It is the lanthanide that reacts most vigorously with water, releasing hydrogen with effervescence. The reaction resembles that of calcium.
2 Eu + 6 HCl → 2 EuCl₃ + 3 H₂
It dissolves readily in acids giving colorless europium(III) salts, which glow bright red under ultraviolet light.
2 EuCl₃ + Zn → 2 EuCl₂ + ZnCl₂
With mild reducing agents it goes to europium(II), which precipitates and allows it to be separated from the rest of the lanthanides: the classic trick of its purification.
Notable compounds
| Compound | Formula | Use or importance |
|---|---|---|
| Europium oxide | Eu₂O₃ | Red phosphor for screens and LEDs |
| Doped yttrium orthoborate | YBO₃:Eu | Red for televisions and lamps |
| Europium(II) sulfide | EuS | Magnetic and optical material |
| Europium chloride | EuCl₃ | Purification and phosphors |
| Beta-diketonate complexes | Eu(tta)₃ | Security inks for banknotes |
Electron shell distribution
View in the atom builderIsotopes
Natural europium combines europium-151 (¹⁵¹Eu, ~47.8%) and europium-153 (¹⁵³Eu, ~52.2%), both with 63 protons. 151Eu is a primordial radionuclide with a very long half-life and decays so slowly that it is considered stable in practice. 153Eu, stable, is used as a target to produce medical samarium-153.
Occurrence and production
It is one of the scarcest lanthanides, at about 2 ppm, in bastnasite and monazite. Its separation takes advantage of its +2 state: it is reduced and precipitated while the others remain as +3. The main deposits are in China and the United States. The metal is obtained by electrolysis or reduction with lanthanum in tantalum crucibles.
History and origin of the name
Eugène-Anatole Demarçay separated it in 1901 by fractional crystallization from samarium and named it europium, after Europe: continental pride in the middle of the rare-earth race. Its purity was achieved thanks to Urbain and Jantsch. For decades it was a laboratory curiosity until color televisions turned it into the red of every home.
Applications and relevance of europium
Uses of the element
As a metal it is barely used free because of its reactivity; its value lies in doping matrices. Small amounts in alloys and nuclear targets absorb neutrons and serve as a burnable poison in reactors.
Uses of its compounds
The oxide and the doped orthoborates produce the red of LEDs, fluorescent lamps and screens, and the blue of some phosphors. Europium complexes tint the security inks of euro banknotes, which glow under ultraviolet light.
Health, safety and environment
Biological role
It has no biological function and is poorly absorbed. The phosphors in screens and lamps are vitrified and pose no exposure. Only industrial dust requires control like any mineral dust.
Safety
The metal can ignite in air and release hydrogen with water, so it is handled dry and under argon. The phosphor compounds are stable in the final product and do not release europium with use.
Environment
Its mining shares the impacts of the rare earths, worsened by its low grade: more rock per kilo. In return, every gram in LEDs saves energy for years. Recycling lamp phosphors recovers europium and yttrium.
Frequently asked questions about Europium
Why is europium important in LED lights?
Europium is essential in many phosphors that convert the blue light of an LED into white light. Some europium compounds emit red light and others blue light, and their combination with other emitters allows the tone, color temperature and color rendering of the lighting to be tuned. Thanks to this, LED bulbs can offer warm, neutral or cool light with low energy consumption.
Is europium dangerous?
Metallic europium is reactive: it can ignite on contact with air and release flammable hydrogen when it reacts with water, so its handling requires controlled industrial conditions. In contrast, the europium compounds used in phosphors and electronic devices are built into solid materials and do not represent a habitual exposure for the user. The relevant risks are associated with the pure metal, fine powders or specific chemical compounds.
What does europium have to do with euro banknotes?
Some europium compounds have fluorescence properties under ultraviolet light, so they have been used in document security systems. In certain banknotes and documents, these materials can emit visible colors when exposed to UV radiation, making counterfeiting harder. Europium is not visible to the naked eye on the banknote, but its compounds can be part of inks or security marks designed to respond to a specific light source.
Why does europium emit red or blue light?
The emission depends on the oxidation state and the chemical environment of europium. In some compounds the europium ion emits its characteristic red light; in others it can produce bluish emissions. This capacity is due to electronic transitions within the ion, which release energy as visible light when returning to a lower-energy state. For this reason, europium is a very versatile material for designing phosphors with precise colors.
What is europium used for in screens and televisions?
Europium compounds are used as red phosphors in screens, televisions and display devices. When they receive energy, these materials emit intense, stable red light, a component needed to reproduce realistic colors. Although screen technologies have evolved, europium remains relevant in phosphors and specialized luminescent materials. Its role is to convert invisible energy or energy of another wavelength into visible light of a concrete color.
Why is europium considered a rare earth?
Europium belongs to the rare earths because it shares geological origin, chemical properties and production methods with other lanthanides. It is not necessarily scarce in absolute terms, but it appears in low concentrations within minerals such as bastnasite and monazite, mixed with very similar elements. Separating it requires sophisticated purification processes. That difficulty of extraction and separation, more than its total abundance, explains its strategic value.
Where does europium come from?
Europium is obtained from rare-earth minerals, mainly bastnasite and monazite, where it appears alongside lanthanum, cerium, neodymium and other lanthanides. After chemical treatment of the ore, solvent extraction and ion exchange techniques are applied to isolate it with high purity. It can then be transformed into europium oxide, the usual form for manufacturing phosphors and luminescent materials.
Main sources consulted: PubChem, Royal Society of Chemistry, NIST, IUPAC. Last revision: November 2026.