Europium is a Lanthanide or a rare earth metal. Its silvery white
The element shows an interesting nuclear feature. Eu 147 and Eu 148 both show weak alpha decay branches. This is a consequence of their having 2 and 3 more neutrons than the closed-shell number of N = 82. (This alpha-instability above a closed neutron shell is what makes Po through At so unstable.) In addition, Eu 151 emits alpha particles, another consequence of its position slightly above a closed neutron shell.