 Europium is the most reactive rare earth element . It rapidly oxidizes in air , so that bulk oxidation of a centimeter @-@ sized sample occurs within several days . Its reactivity with water is comparable to that of calcium , and the reaction is 
 Europium <a href='drop_aux' title='1'><mark>is</mark></a>the most reactive rare earth element . It rapidly <a href='uninflect' title='2'><mark>oxidizes</mark></a> in air , so that bulk oxidation of a centimeter @-@ sized sample <a href='uninflect' title='3'><mark>occurs</mark></a> within several days . Its reactivity with water <a href='drop_aux' title='4'><mark>is</mark></a>comparable to that of calcium , and the reaction is 
Europium da most reactive rare earth element . It rapidly oxidize in air , so dat bulk oxidation of a centimeter @-@ sized sample occur within several days . Its reactivity w water comparable to that of calcium , and tdareaction is