Europium

63 samariumeuropiumgadolinium
-

Eu

Am
Eu-TableImage.png
General
Name, Symbol, Number europium, Eu, 63
Chemical series lanthanides
Group, Period, Block n/a, 6, f
Appearance silvery white
Eu,63.jpg
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/cm³
Liquid density at m.p. 5.13 g/cm³
Melting point 1099 K
(826 °C, 1519 °F)
Boiling point 1802 K
(1529 °C, 2784 °F)
Heat of fusion 9.21 kJ/mol
Heat of vaporization 176 kJ/mol
Heat capacity (25 °C) 27.66 J/(mol·K)
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 simple cubic (body centered)
Oxidation states 3,2
(mildly basic oxide)
Electronegativity  ? 1.2 (Pauling scale)
Ionization energies
(more)
1st: 547.1 kJ/mol
2nd: 1085 kJ/mol
3rd: 2404 kJ/mol
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·K)
Thermal expansion (r.t.) (poly)
35.0 µm/(m·K)
Speed of sound (thin rod) (r.t.) 18.2 m/s
Shear modulus 7.9 GPa
Bulk modulus 8.3 GPa
Poisson ratio 0.152
Vickers hardness 167 MPa
CAS registry number 7440-53-1
Notable 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

Europium (chemical symbol Eu, atomic number 63) is the most reactive of the rare earth elements.[1] It was named after the continent Europe.

Contents

Occurrence

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

History

Europium was first found by Paul Émile Lecoq de Boisbaudran in 1890, who obtained basic fractions 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.

Notable characteristics

Europium is an inner transition metal (or lanthanide) that lies in period six of the periodic table, between samarium and gadolinium. 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.

Isotopes

Naturally occurring europium is composed of two stable isotopes, 151-Eu and 153-Eu, with 153-Eu being the most abundant (52.2 percent 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-lives that are less than 4.7612 years, and the majority of these have half lives that are less than 12.2 seconds. This element also has eight meta states, with the most stable being 150m-Eu (t½ 12.8 hours), 152m1-Eu (t½ 9.3116 hours) and 152m2-Eu (t½ 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.

Compounds

Europium compounds include:

Europium(II) compounds tend to predominate, in contrast to most lanthanides (which generally form compounds with an oxidation state of +3). Europium(II) chemistry is very similar to barium(II) chemistry, as they have similar ionic radii.

Applications

There are few commercial applications for europium metal. It has been used to dope some types of glass to make lasers, and 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 interrogate biomolecular interactions in drug-discovery screens. It is also used in the anti-counterfeiting phosphors in Euro banknotes.[2]

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.

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.

See also

Notes

  1. The term "rare earth elements" (or "rare earth metals") is a trivial name applied to 16 chemical elements: scandium, yttrium, and 14 of the 15 lanthanides (excluding promethium), which occur naturally on Earth. Some definitions also include the actinides. The word "earth" is an obsolete term for oxide. The term "rare earth" is discouraged by the International Union of Pure and Applied Chemistry (IUPAC), as these elements are relatively abundant in the Earth's crust.
  2. "Articles and gems - Europium in Euros" SmarterScience. Retrieved October 8, 2007.

References

  • Chang, Raymond. 2006. Chemistry. 9th ed. New York: McGraw-Hill Science/Engineering/Math. ISBN 0073221031
  • Cotton, F. Albert, and Geoffrey Wilkinson. 1980. Advanced Inorganic Chemistry. 4th ed. New York: Wiley. ISBN 0-471-02775-8
  • "Europium" Los Alamos National Laboratory, Chemistry Division. Retrieved October 8, 2007.
  • Greenwood, N.N. and A. Earnshaw. 1998. Chemistry of the Elements. 2nd ed. Oxford, U.K.; Burlington, MA: Butterworth-Heinemann, Elsevier Science. ISBN 0750633654 Online version Retrieved October 8, 2007.
  • Jones, Adrian P., Frances Wall, and C. Terry Williams, eds. 1996. Rare Earth Minerals: Chemistry, Origin and Ore Deposits. The Mineralogical Society Series. London, UK: Chapman and Hall. ISBN 0412610302
  • Stwertka, Albert. 1998. Guide to the Elements. Rev. ed. Oxford, UK: Oxford University Press. ISBN 0-19-508083-1

External links

All links retrieved August 10, 2017.

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