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Element Fact
Iridium is the most corrosion-resistant metal known. Together with platinum, it is used to make the international prototype of the kilogram, which is the standard definition for the unit of mass.

Europium, Eu

europium sample

Atomic number: 63
Atomic mass: 151.964(1)
Natural abundance: 2.1 ppm
151Eu (150.919846) - 47.8%
153Eu (152.921226) - 52.2%

History and Production

Derived from the word Europe. First identified from a mixture of samarium and gadolinium sample by P.- Lecoq de Boisbaudran in 1890. However, it was first isolated in rather pure form by E.-A. Demarcay in 1901. The metal can now be isolated by electrolysis of fused halides and by reduction of its oxide by lanthanum metal. It is a good neutron absorber and has potential use as nuclear reactor control rods. It is used as a red phospher activator in color TV tubes. It is also used as an agent for the manufacture of fluorescent glass.

Physical Data

It is silvery-white that quickly reacts in air and in water. Earth's crust contains about 2.1 ppm of europium which is often associated with other rare earth metals in nature in monazite, bastnaesite, gadolinite etc.

Interatomic distance: 399 pm
Melting point: 822C
Boiling point: 1596C
Thermal conductivity/Wm-1K-1: 13.9 (27C)
Density/kgm-3: 5243 (20C)

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: 175.3 kJ/mol
Gibbs free energy of formation: 142.2 kJ/mol
Entropy: 188.8 J/mol K
Heat capacity: 20.8 J/mol K

Electronic data

Electronic configuration: [Xe] 4f7 6s2
Term symbol: 8S7/2
Electron affinity: -   Electronegativity (Pauline): -
Ionization energy (first, second, third): 547.111, 1084.59, 2404.42 kJ/mol

Chemical properties

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