Praseodymium (Pr)

Praseodymium ([Xe]5f³6s²) (CAS 7440-10-0) is a soft, silvery-yellow, malleable, ductile metal. Praseodymium is never found free in nature, appearing only in combined form with other rare earths in various minerals. More resistant to corrosion in air than some other rare earths, it develops a green oxide coating that spalls off when exposed to air. It should be stored under mineral oil or in an inert atmosphere. Similar to other rare earths, praseodymium forms brightly colored compounds.