Europium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements

63 samarium ← europium → gadolinium - ↑ Eu ↓ Am Periodic Table - Extended Periodic Table
General
Name, Symbol, Number	europium, Eu, 63
Chemical series	lanthanides
Group, Period, Block	n/a, 6, f
Appearance	silvery white
Atomic mass	151.964 (1) g/mol
Electron configuration	[Xe] 4f7 6s2
Electrons per shell	2, 8, 18, 25, 8, 2
Physical properties
Phase	solid
Density (near r.t.)	5.264 g·cm−3
Liquid density at m.p.	5.13 g·cm−3
Melting point	1099  K (826 ° C, 1519 ° F)
Boiling point	1802 K (1529 ° C, 2784 ° F)
Heat of fusion	9.21 kJ·mol−1
Heat of vaporization	176 kJ·mol−1
Heat capacity	(25 °C) 27.66 J·mol−1·K−1
Vapor pressure P/Pa 1 10 100 1 k 10 k 100 k at T/K 863 957 1072 1234 1452 1796
Atomic properties
Crystal structure	cubic body centered
Oxidation states	3,2 (mildly basic oxide)
Electronegativity	? 1.2 (Pauling scale)
Ionization energies ( more)	1st: 547.1 kJ·mol−1
	2nd: 1085 kJ·mol−1
	3rd: 2404 kJ·mol−1
Atomic radius	185 pm
Atomic radius (calc.)	231 pm
Miscellaneous
Magnetic ordering	no data
Electrical resistivity	( r.t.) (poly) 0.900 µΩ·m
Thermal conductivity	(300 K) est. 13.9 W·m−1·K−1
Thermal expansion	( r.t.) (poly) 35.0 µm/(m·K)
Young's modulus	18.2 GPa
Shear modulus	7.9 GPa
Bulk modulus	8.3 GPa
Poisson ratio	0.152
Vickers hardness	167 MPa
CAS registry number	7440-53-1
Selected isotopes
Main article: Isotopes of europium iso NA half-life DM DE ( MeV) DP 150Eu syn 36.9 y ε 2.261 150Sm 151Eu 47.8% Eu is stable with 88 neutrons 152Eu syn 13.516 y ε 1.874 152Sm β- 1.819 152Gd 153Eu 52.2% Eu is stable with 90 neutrons
References

Europium ( IPA: /jʊˈrəʊpiəm/) is a chemical element in the periodic table that has the symbol Eu and atomic number 63. It was named after the continent Europe.

Notable characteristics

Europium is the most reactive of the rare earth elements; it instantly oxidizes in air, and resembles calcium in its reaction with water; deliveries of the metal element in solid form even under mineral oil are rarely shiny. Europium ignites in air at about 150 °C to 180 °C. It is about as hard as lead and quite ductile.

Applications

There are few commercial applications for europium metal, although it has been used to dope some types of glass to make lasers, as well as being used for screening for Down syndrome and some other genetic diseases. Due to its ability to absorb neutrons, it is also being studied for use in nuclear reactors. Europium oxide (Eu₂O₃) is widely used as a red phosphor in television sets and fluorescent lamps, and as an activator for yttrium-based phosphors. It is also being used as an agent for the manufacture of fluorescent glass. Europium fluorescence is used to interogate biomolecular interactions in drug-discovery screens. It is also used in the anti-counterfeiting phosphors in Euro banknotes.

Europium is commonly included in trace element studies in geochemistry and petrology to understand the processes that form igneous rocks (rocks that cooled from magma or lava). The nature of the europium anomaly found is used to help reconstruct the relationships within a suite of igneous rocks.

History

Europium was first found by Paul Émile Lecoq de Boisbaudran in 1890, who obtained basic fraction from samarium-gadolinium concentrates which had spectral lines not accounted for by samarium or gadolinium; however, the discovery of europium is generally credited to French chemist Eugène-Antole Demarçay, who suspected samples of the recently discovered element samarium were contaminated with an unknown element in 1896 and who was able to isolate europium in 1901.

Occurrence

Europium is never found in nature as the free element; however, there are many minerals containing europium, with the most important sources being bastnasite and monazite. Europium has also been identified in the spectra of the sun and certain stars.

Compounds

Europium compounds include:

• Fluorides
  • EuF₂
  • EuF₃
• Chlorides
  • EuCl₂
  • EuCl₃
• Bromides
  • EuBr₂
  • EuBr₃
• Iodides
  • EuI₂
  • EuI₃
• Oxides
  • Eu₂O₃
  • Eu₃O₄
• Sulfides
  • EuS
• Selenides
  • EuSe
• Tellurides
  • EuTe
• Nitrides
  • EuN

Europium(II) compounds tend to predominate, which is a slight exception as most lanthanides form compounds with an oxidation state of +3. Europium(II) chemistry is very similar to barium(II) chemistry, as they have similar ionic radii. See also europium compounds.

Isotopes

Naturally occurring europium is composed of 2 stable isotopes, 151-Eu and 153-Eu, with 153-Eu being the most abundant (52.2% natural abundance). 35 radioisotopes have been characterized, with the most stable being 150-Eu with a half-life of 36.9 years, 152-Eu with a half-life of 13.516 years, and 154-Eu with a half-life of 8.593 years. All of the remaining radioactive isotopes have half-lifes that are less than 4.7612 years, and the majority of these have half lifes that are less than 12.2 seconds. This element also has 8 meta states, with the most stable being 150m-Eu (t_½ 12.8 hours), 152m1-Eu (t_½ 9.3116 hours) and 152m2-Eu (t_½ 96 minutes).

The primary decay mode before the most abundant stable isotope, 153-Eu, is electron capture, and the primary mode after is beta minus decay. The primary decay products before 153-Eu are element Sm (samarium) isotopes and the primary products after are element Gd (gadolinium) isotopes.

Precautions

The toxicity of europium compounds has not been fully investigated, but there are no clear indications that europium is highly toxic compared to other heavy metals. The metal dust presents a fire and explosion hazard. Europium has no known biological role.