Chemical element · reference page

63Eu

Europium

Europium is element 63 (Eu), located in period 6, group — and the f block. At room temperature its reference phase is solid. Its electron configuration is [Xe] 4f7 6s2.

Atomic number63

Standard atomic weight151.964(1)

Group—

Period6

Blockf

Electron configuration[Xe] 4f7 6s2

Electronic structure

What controls its chemistry

The lanthanides are characterised by filling of the 4f subshell. Their chemistry is often dominated by the +3 oxidation state, while partially filled f orbitals give many members useful magnetic and optical properties.

Because the 4f electrons are relatively shielded, neighbouring lanthanides have very similar chemical behaviour. Separating them from one another is therefore much harder than separating elements from different main groups.

Chemical forms

Compounds, ions and materials

Lanthanides are commonly encountered as +3 ions in oxides, halides and coordination compounds. Their compounds often have closely related chemistry, while differences in f-electron structure create distinctive magnetic and luminescent behaviour.

Physical behaviour

State and phase changes

The reference phase at room temperature is solid. The listed density is 5.244g/cm³. The melting point is 1 095 K (821.9 °C). The boiling point is 1 802 K (1 529 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where europium is found and used

In practice, europium is encountered in phosphors, security inks and lasers.

In practice

Examples of real uses

Phosphors

Europium is used in luminescent materials that absorb energy and emit visible light at characteristic wavelengths.

Security inks

Luminescent europium compounds provide distinctive optical signatures for anti-counterfeiting features.

Lasers

Europium is used in laser media, optical components or wavelength-specific light generation.

Periodic position

What its neighbours tell us

Europium is in period 6. In the f-block sequence shown here, it appears between samarium and gadolinium. This sequence allows a direct comparison with the neighbouring f-block elements.

Reference data

Physical and atomic properties

Classificationlanthanide

Phase at room temperatureSolid

Electron shells2 · 8 · 18 · 25 · 8 · 2

Density5.244g/cm³

Melting point1 095 K (821.9 °C)

Boiling point1 802 K (1 529 °C)

Pauling electronegativity—

First ionisation energy547.1 kJ/mol

Electron affinity11.2 kJ/mol

Values describe the element or neutral atom where applicable. Physical data can depend on allotrope, pressure and measurement conditions.

History

Discovery and identification

The discovery of europium is associated with Eugène-Anatole Demarçay. Recognition of the element, isolation of a pure sample and assignment of its modern atomic number did not necessarily occur at the same time.

Isotopes and atomic weight

How isotope composition changes the numbers

The standard atomic weight is 151.964(1). This value refers to the isotopic composition of natural terrestrial material, not to the mass of one specific atom.

Europium has at least one stable isotope. Different isotopes have the same number of protons and therefore the same element identity, but different neutron numbers and atomic masses.

Safety

Handling and exposure

The hazards associated with europium depend on chemical form, dose and route of exposure. Pure europium, its ions and its compounds can have very different biological and environmental effects, so safety data should be checked for the actual substance being handled.