a radioactive metallic element that is similar to tellurium and bismuth; occurs in uranium ores but can be produced by bombarding bismuth with neutrons in a nuclear reactor
A radioactive element that occurs in pitchblende and other uranium containing ores
A radioactive isotope of polonium, 21084Po, having a half-life of 140 days; it as used as a reference alpha emitter in the calibration of radiation counters