Not until an hour after the patients arrived was it established that they had come into contact with the radioactive isotope caesium-137.

Scientists have found traces of the radioactive isotope polonium-210 in his body and possessions.

I will take a capsule of a highly radioactive isotope of iodine, 131, that will destroy any thyroid tissue remaining.

Upon collision with a neutrino, a chlorine atom transforms into a radioactive isotope of argon, which can then be extracted and counted.

Among elements with a known stable isotope, only tellurium and rhenium similarly occur with a stable isotope in lower abundance than the long-lived radioactive isotope.