Why promethium is radioactive?
Score: 4.7/5 (30 votes) Promethium is the only rare earth, radioactive metal on the periodic table, according to Chemicool. ... It can be produced by bombarding neodymium-146 with neutrons to become neodymium-147, which beta decays over its 11-day half-life into promethium-147, according to the Jeff...