| Term | Definition |
| a word which describes an isotope that undergoes fission | unstable |
| a nuclear reaction that involves splitting a heavy nucleus into a lighter nucleus | fission |
| the part of an atom that contains protons and neutrons | nucleus, nucleon |
| two neutrons and two protons are released in this type of decay | alpha decay |
| the type of nuclear reaction taking place on the sun | fusion |
| the form of electromagnetic radiation released during radioactive decay | gamma rays |
| the average time for half the amount of a radioactive element to decay | half-life |
| what is nuclear power | fission |