Definition that contains mass number
- radiothorium radioactive isotope of thorium with mass number 228
- uranium 235 a uranium isotope with mass number 235; capable of sustaining chain reactions
- cobalt 60 a radioactive isotope of cobalt with mass number 60; a source of exceptionally intense gamma rays; used in radiation therapy
- strontium 90 a radioactive isotope of strontium (with the mass number 90) that is present in the fallout from nuclear explosions; can be assimilated like calcium into bones
- boson any particle that obeys Bose-Einstein statistics but not the Pauli exclusion principle; all nuclei with an even mass number are bosons
- thorium-228 radioactive isotope of thorium with mass number 228