- Europium (Eu) is a soft, silvery metal with atomic number 63, belonging to the lanthanide series of the periodic table.
- It has an electron configuration of [Xe] 4f⁷ 6s², giving it a half-filled 4f subshell, which contributes to its distinctive chemical behavior.
- Europium most commonly forms the Eu³⁺ ion, though the Eu²⁺ oxidation state is unusually stable for a lanthanide and is important in several of its compounds. The atomic structure contains sixty-three protons, typically eighty-nine or ninety neutrons, and sixty-three electrons arranged in six shells.
- Naturally occurring europium is composed of two stable isotopes: europium-151 (¹⁵¹Eu, about 47.8%) and europium-153 (¹⁵³Eu, about 52.2%).
- Europium is never found as a pure metal in nature but occurs in rare earth minerals such as monazite ((Ce,La,Nd,Th)PO₄) and bastnäsite ((Ce,La)(CO₃)F), often in very low concentrations. Major sources are mined in China, with smaller deposits in the USA, Brazil, India, and Australia. Extraction involves separation from other lanthanides through ion-exchange and solvent extraction processes.
- The element was discovered in 1901 by French chemist Eugène-Anatole Demarçay, who isolated it from samarium-containing materials after noting unexplained spectral lines in earlier studies. Europium was named after the continent of Europe, marking it as one of the few elements named for a geographical region.
- Europium is best known for its remarkable luminescent properties. Compounds such as europium(III) oxide (Eu₂O₃) and europium-doped phosphors are used extensively in the red and blue components of fluorescent and LED lighting, television screens, and computer monitors. In particular, europium-doped yttrium oxide (Y₂O₃:Eu³⁺) produces the bright red phosphor essential in cathode-ray tubes and plasma displays. Europium(II)-doped phosphors are also critical in producing the blue light in modern high-brightness LEDs. Because of its strong ability to absorb neutrons, europium-151 is used as a control material in nuclear reactors. Europium-based compounds are also employed in anti-counterfeiting measures, including banknotes and passports, where they provide unique spectral signatures under UV light.
- Chemically, europium is one of the most reactive rare earth metals. It oxidizes rapidly in air, forming a dull oxide layer, and reacts quickly with water, producing europium hydroxide and hydrogen gas. In its +2 oxidation state, europium forms salts such as europium(II) chloride (EuCl₂) that are pale yellow and strongly reducing. The +3 state, by contrast, forms colorless to pale pink compounds that are relatively stable.
- Biologically, europium has no known essential role in living organisms. Its compounds are generally of low toxicity, but as with all fine powders and soluble salts, ingestion or inhalation should be avoided.
- From an environmental perspective, europium in mineral form is stable and poses little direct hazard, but its extraction from rare earth ores involves chemical processes that can produce environmentally harmful waste, particularly if radioactive by-products from thorium- or uranium-containing minerals are not properly managed.
