Europium

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The chemical element europium is classed as a lanthanide and rare earth metal. It was discovered in 1901 by Eugène-Antole Demarçay.

Data Zone

Classification:	Europium is a lanthanide and rare earth metal
Color:	silvery-white
Atomic weight:	151.96
State:	solid
Melting point:	822 ^oC, 1095 K
Boiling point:	1600 ^oC, 1873 K
Electrons:	63
Protons:	63
Neutrons in most abundant isotope:	90
Electron shells:	2,8,18,25,8,2
Electron configuration:	[Xe] 4f⁷ 6s²
Density @ 20^oC:	5.248 g/cm³

Show more, including: Heats, Energies, Oxidation,
Reactions, Compounds, Radii, Conductivities

Atomic volume:	20.8 cm³/mol
Structure:	bcc: body-centered cubic
Hardness:
Specific heat capacity	0.18 J g^-1 K^-1
Heat of fusion	9.210 kJ mol^-1
Heat of atomization	178 kJ mol^-1
Heat of vaporization	175.73 kJ mol^-1
1^st ionization energy	546.7 kJ mol^-1
2^nd ionization energy	1085 kJ mol^-1
3^rd ionization energy	2405 kJ mol^-1
Electron affinity	–
Minimum oxidation number	0
Min. common oxidation no.	0
Maximum oxidation number	3
Max. common oxidation no.	3
Electronegativity (Pauling Scale)	1.12
Polarizability volume	27.7 Å³
Reaction with air	vigorous, ⇒ Eu₂O₃
Reaction with 15 M HNO₃	mild, ⇒ Eu(NO₃)₃
Reaction with 6 M HCl	mild, ⇒ H₂, EuCl₃
Reaction with 6 M NaOH	–
Oxide(s)	Eu₂O₃ (Europia)
Hydride(s)	EuH₂
Chloride(s)	EuCl₃
Atomic radius	185 pm
Ionic radius (1+ ion)	–
Ionic radius (2+ ion)	131 pm
Ionic radius (3+ ion)	108.7 pm
Ionic radius (1- ion)	–
Ionic radius (2- ion)	–
Ionic radius (3- ion)	–
Thermal conductivity	13.9 W m^-1 K^-1
Electrical conductivity	1.1 x 10⁶ S m^-1
Freezing/Melting point:	822 ^oC, 1095 K

Fittingly, europium is used in the euro currency as an anti-forgery measure. Shining UV light on a euro results in red fluorescence from europium Eu³⁺, blue from thulium Tm³⁺ and green from terbium Tb³⁺.

Discovery of Europium

Dr. Doug Stewart

The story of Europium’s discovery begins with the discovery of another element – samarium.

French chemist Paul-Émile Lecoq de Boisbaudran claimed to have isolated samarium in 1879; others believed that one or more other new rare earth elements were present in Boisbaudran’s sample.

In 1886, French chemist Eugène-Antole Demarçay identified spectroscopic lines in ‘samarium’ caused by the element we now know as europium. ⁽¹⁾

He achieved this using a new spectroscope he had developed to study the rare earths.

Demarçay’s spectroscope had a special induction coil which produced a very high spark temperature and used platinum electrodes to remove all other spectral lines. ⁽²⁾

Demarçay’s spectral results were disputed and he realized that he needed further proof.

He obtained this in 1901, when he successfully isolated europium using repeated crystallizations of samarium magnesium nitrate. ^(1),(3)

He named the new element after the continent of Europe.

In 1904 europium was separated from impure gadolinium by French chemist Georges Urbain using bismuth magnesium nitrate. Urbain discovered that bismuth nitrate will often crystallize between two fractions of rare earth elements making it easier to separate them. ⁽¹⁾

Europium is used to produce blue, red and white radiances in computer monitors and television screens. It is also used in energy efficient light bulbs.

A brief introduction to the lanthanides.

Appearance and Characteristics

Harmful effects:

Europium is considered to be mildly toxic. The metal dust is considered to be a fire and explosion hazard.

Characteristics:

Europium is a soft, ductile, silvery-white metal that instantly oxidizes in air.

It is the most reactive of the rare earth metals and ignites in air at temperatures in excess of 150 ^oC to 180 ^oC.

In water it reacts in a similar way to calcium, producing europium hydroxide and hydrogen gas.

Unlike most other rare earth metals, europium can form stable compounds in the divalent state, Eu²⁺ (europous) as well as the usual trivalent state, Eu³⁺ (europic).

Uses of Europium

Europium oxide (europia) is widely used as a doping agent in phosphors in television sets and computer monitors: valency three europium produces a red radiance and valency two europium produces a blue radiance. When both valencies are combined a white light is produced which is used in compact fluorescent bulbs.

Europium is also used in phosphors in anti-forgery marks on Euro bank notes.

Europium isotopes are good neutron absorbers and are used in nuclear reactor control rods.

Abundance and Isotopes

Abundance earth’s crust: 1.8 parts per million by weight, 0.2 parts per million by moles

Abundance solar system: 0.5 part per billion by weight, 4 parts per trillion by moles

Cost, pure: $1350 per g

Cost, bulk: $20,000 per 100g

Source: Europium is not found free in nature but is found in a number of minerals mainly monazite, bastnaesite and xenotime. Commercially, europium is isolated by ion exchange and solvent extraction. The pure metal can be produced by the electrolysis of the molten chloride with sodium chloride.

Isotopes: Europium has 30 isotopes whose half-lives are known, with mass numbers 131 to 162. Naturally occurring europium is a mixture of its two stable isotopes, ¹⁵¹Eu and ¹⁵³Eu with natural abundances of 47.8% and 52.2% respectively.

References

Ferenc Szabadváry, Handbook of the Chemistry and Physics of the Rare Earths Vol. 11., Elsevier Science Publishers., 1998, p65.
Per Enghag, Encyclopedia of the elements: technical data, history, processing, applications., John Wiley and Sons, 2004, page 450.
John Emsley, Nature’s building blocks: an A-Z guide to the elements., Oxford University Press, 2003, p140.

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