Soft Metal, Symbol La, Used as a Catalyst
Puzzle 14 of Periodic Table Medium Pack
Question is: Soft Metal, Symbol La, Used as a Catalyst
and the answer is: LANTHANUM
Word Meaning:
LANTHANUM — (uncountable) A chemical element (symbol La) with an atomic number of 57: a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air.
Definitions from Wiktionary.