phosphorus 32

noun

-ˌthərt-ē-ˈtü 

: a heavy radioactive isotope of phosphorus having a mass number of 32 and a half-life of 14.3 days that is produced in nuclear reactors and used chiefly in tracer studies (as in biology and in chemical analysis) and in medical diagnosis (as in location of tumors)

—symbol P³² or ³²P