 = Europium = 
 
 Europium is a chemical element with symbol Eu and atomic number 63 . It was isolated in 1901 and is named after the continent of Europe . It is a moderately hard , silvery metal which readily oxidizes in air and water . Being a typical member of the lanthanide series , europium usually assumes the oxidation state + 3 , but the oxidation state + 2 is also common : all europium compounds with oxidation state + 2 are slightly reducing . Europium has no significant biological role and is relatively non @-@ toxic compared to other heavy metals . Most applications of europium exploit the phosphorescence of europium compounds . Europium is one of the least abundant elements in the universe ; only about 5 × 10 − 8 % of all matter in the universe is europium . 
 
 = = Characteristics = = 
 
 
 = = = Physical properties = = = 
 
 Europium is a ductile metal with a hardness similar to that of lead . It crystallizes in a body @-@ centered cubic lattice . Some properties of europium are strongly influenced by its half @-@ filled electron shell . Europium has the second lowest melting point and the lowest density of all lanthanides . 
 Europium becomes a superconductor when it is cooled below 1 @.@ 8 K and compressed to above 80 GPa . This is because europium is divalent in the metallic state , and is converted into the trivalent state by the applied pressure . In the divalent state , the strong local magnetic moment ( J 