These elements are vanadium, rubidium, indium, lanthanum, europium, rhenium and lutetium. These elements are vanadium, rubidium, indium, lanthanum, europium, lutetium, and rhenium. The metals that can be extracted from it include&colon; cerium, lanthanum, neodymium, and europium. Samarium purification follows the removal of the europium. Gadolinium-153 is produced in a nuclear reactor from elemental europium or enriched gadolinium targets. This isotope is produced in a nuclear reactor from europium or enriched gadolinium. Europium compounds tend to exist trivalent oxidation state under most conditions. Europium and ytterbium form salt-like monoxides, EuO and YbO, which have a rock salt structure. The fractional crystallization of the oxides then yielded "europium" in 1901. Most applications of europium exploit the phosphorescence of europium compounds. Europium fluorescence is used to interrogate biomolecular interactions in drug-discovery screens. In Europe, Europium and fluorescing dye are combined on Euros. However, a package duly arrived in the mail, containing several pounds of genuine europium oxide. All europium compounds with oxidation state +2 are slightly reducing. Some properties of europium are strongly influenced by its half-filled electron shell.