Quick Quiz: Nouns Score: Change category, Flip order Reset Correct! Noun: atomic number 100 Your choice? a radioactive transuranic metallic element produced by bombarding plutonium with neutrons a white trivalent metallic element; sometimes classified in the rare earth group; occurs in the Scandinavian mineral thortveitite a rare heavy polyvalent metallic element that resembles manganese chemically and is used in some alloys; is obtained as a by-product in refining molybdenum a small conical pouch projecting from the upper anterior part of each atrium of the heart