Answer: praseodymium

AnswerCrossword Clue
praseodymiuma chemical element, a metal with green salts, isolated from the once-supposed element didymium
praseodymiumrare-earth, metallic, trivalent element, named from its green salts. Symbol: Pr; at. wt.: 140.91; at. no.: 59; sp. gr.: 6.77 at 20┬░C