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History

Europium was first found by Paul Emile 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 Eugene-Antole Demarcay, 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.

Named for the continent of Europe, the element ranks thirteenth in abundance among the rare earth metals, but there is more of it than silver and gold combined.

Characteristics

The pure metal was not isolated until recent years.  Europium is now prepared by, mixing Eu₂O₃ with a 10%-excess of lanthanum metal and heating the mixture in a tantalum crucible under high vacuum.  The element is collected as silvery-white metallic deposit on the walls of the crucible.  Europium is about as hard as lead and is quite ductile.  It is the most reactive of the rare-earth metals, quickly oxidizing in air.  Bastnasite and monazite are the principal ores containing europium.  Europium has been identified spectroscopically in the sun and certain stars.  Europium isotopes are good neutron absorbers and are being studied for use in nuclear control applications. 

Generally refined from monazite sand, the pure metal has few applications, but you would find it less interesting to read this without some of its compounds which are used as activators and red phosphors in color CRT screens for television and computers.

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.

Occurrence

Europium is never found in nature as a 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.

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 Snydrome 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.

Compounds

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.

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).  36 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 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.