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Europium

physical science Maturity 7-9 Next article →

Europium is a chemical element with the symbol Eu and atomic number 63. It is a silvery-white metal belonging to the lanthanide series.

Eu-Block
Eu-Block

This metal is unique among its group because it is the most chemically reactive, the least dense, and the softest of the lanthanides. It is so soft that it can be cut with a knife. Because it reacts so readily with air, it quickly forms a dark oxide coating.

Europium on air oxidized
Europium on air oxidized

While it is a metal, it is also one of the rarest of the rare-earth elements found on Earth.

The chemical behavior of europium is driven by its oxidation states. Most lanthanides almost exclusively form compounds with an oxidation state of +3. However, europium can readily form divalent compounds, meaning it has an oxidation state of +2. This happens because the +2 state provides a half-filled f-shell electron configuration, which offers extra stability.

Eu-sulfate-luminescence
Eu-sulfate-luminescence

In this +2 state, europium acts as a mild reducing agent. This means it can donate electrons to other substances, causing them to oxidize. In certain anaerobic or geothermal conditions, this divalent form is stable enough to be incorporated into minerals containing calcium.

Europium's reactivity leads to many different types of chemical compounds. When it reacts with halogens, it can form various halides. For example, it creates white europium(III) fluoride and yellow europium(III) chloride. It can also form dihalides, such as yellow-green europium(II) fluoride.

Eu-sulfate-luminescence
Eu-sulfate-luminescence

Europium also forms stable compounds with chalcogens like sulfur, selenium, and tellurium. It can exist in multiple oxide forms, including europium(II) oxide and europium(III) oxide. Some specific compounds, like europium(III) sulfate, are soluble in water or polar organic solvents.

Scientists first discovered europium in 1896. The researcher who found it was Eugène-Anatole Demarçay. He chose to name the element after the continent of Europe.

Monazit - Mosambik, O-Afrika
Monazit - Mosambik, O-Afrika

Since that discovery, researchers have identified many different versions of the element called isotopes. Naturally occurring europium consists of two isotopes: 151Eu and 153Eu. These exist in almost equal proportions, though 153Eu is slightly more abundant at 52.2%. While 153Eu is stable, 151Eu is unstable and undergoes alpha decay. Scientists have also characterized 39 artificial radioisotopes in laboratory settings.

Finding europium requires mining specific minerals because it is never found as a free element in nature. The most important sources are minerals like bastnäsite, monazite, xenotime, and loparite-(Ce).

Monazit - Mosambik, O-Afrika
Monazit - Mosambik, O-Afrika

The Bayan Obo deposit in Inner Mongolia is the largest known deposit of rare-earth elements. It contains an estimated 36 million tonnes of rare-earth element oxides. However, europium is only 0.2% of the rare-earth content in that deposit. Another major source was the Mountain Pass mine in California, though its bastnäsite contains only 0.1% europium. To isolate the metal, scientists often use electrolysis on a mixture of molten europium(III) chloride and sodium chloride.

Europium has significant scientific value in several different fields. In geochemistry, researchers study the "negative europium anomaly." This occurs when certain minerals, like monazite, have low europium content compared to other lanthanides. This process helps scientists reconstruct how igneous rocks formed from magma. In astrophysics, astronomers look for the signature of europium in stellar spectra. By measuring the levels of europium relative to iron, they can propose theories about how specific stars were born.

Aperture Grille
Aperture Grille

This helps classify stars and understand the history of the universe.

One of the most famous uses of europium involves its unique optical properties. Many applications exploit the phosphorescence of europium compounds. For instance, some europium(III) compounds fluoresce a bright red under ultraviolet light.

Eu-sulfate-luminescence
Eu-sulfate-luminescence

This property was historically used in cathode ray tube televisions to help produce color.

Aperture Grille
Aperture Grille

Additionally, divalent europium can act as an activator for the bright blue fluorescence seen in some fluorite samples. This connection between europium and light has made it an essential tool in both technology and mineralogy.

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🖼️ Images & Media (6)
File:Eu-Block.jpg
Eu-Block.jpg
File:Europium on air oxidized.jpg
Europium on air oxidized.jpg
File:Eu-sulfate.jpg
Eu-sulfate.jpg
File:Eu-sulfate-luminescence.jpg
Eu-sulfate-luminescence.jpg
File:Monazit - Mosambik, O-Afrika.jpg
Monazit - Mosambik, O-Afrika.jpg
File:Aperture Grille.jpg
Aperture Grille.jpg
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