| Alpha emission | emission of an alpha particle, from an unstable nucleus |
| Atomic number (Z) | the number of protons in the nucleus |
| Beta emission | the emission of a high-speed electron from an unstable nucleus |
| Electron capture | the decay of an unstable nucleus by capturing, or picking up, an electron from an inner orbital of an atom |
| Gamma emission | emission from an excited nucleus of a gamma photon |
| Half-life | the time it takes for the reactant concentration to decrease by one-half of its initial value in a reaction. The time it takes for one-half of the nuclei in a sample to decay |
| Isotopes | atoms whose nuclei have the same atomic number but different mass numbers |
| Mass number (A) | the total number of protons and neutrons in the nucleus |
| Nuclear bombardment reaction | a nuclear reaction in which a nucleus is bombarded, or struck, by another nucleus or by a nuclear particle |
| Nuclear equation | a symbolic representation of a nuclear reaction |
| Nucleus | the central core of an atom; it has most of the mass of the atom and one or more units of positive charge |
| Particle accelerator | device used to accelerate electrons, protons, and alpha particles and other ions to very high speeds |
| Positron emission | emission of a positron from an unstable nucleus |
| Radioactive decay | the process in which a nucleus spontaneously disintegrates, giving off radiation |
| Radioactivity | spontaneous radiation from unstable elements |