Europium

Uncommon card · No. 167677

Europium is a chemical element; it has symbol Eu and atomic number 63. It is a soft, silvery-white lanthanide metal that tarnishes rapidly in air and is the most chemically reactive of the lanthanides. Europium has an unusually low density and large atomic volume for a lanthanide because the metal is effectively divalent, unlike the predominantly trivalent neighbouring elements. Its half-filled 4f7 electron configuration also gives elemental europium distinctive magnetic properties; it is paramagnetic at room temperature and becomes antiferromagnetic below about 91 K. In compounds, the +3 oxidation state is generally the most stable, but europium has the most readily accessible +2 state of any lanthanide. Europium does not occur naturally as the free metal and is found only as a minor component of rare-earth minerals such as bastnäsite, monazite and xenotime. Its ability to form Eu(II) gives it unusual geochemical behaviour: europium can be preferentially incorporated into feldspar, producing...

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