| Radioactivity | The process whereby unstable atomic nuclei break down and emit radiation |
| Alpha Particle | The nucleus of a helium atom which consists of 2 neutrons and 2 protons, ejected by certain radioactive elements |
| Beta Particles | An electron (or positron) emitted during the radioactive decay of certain nuclei |
| Gamma Ray | High-frequency electromagnetic radiation emitted by the nuclei of radioactive atoms |
| Nucleon | A nuclear proton or neutron |
| Half-life | The time required for half the atoms in a sample of a radioactive isotope to decay |
| Transmutation | The conversion of an atomic nucleus of one element into an atomic nucleus of another element through a loss or gain in the number of protons |
| Nuclear fission | The splitting of the nucleus of a heavy atom, such as uranium-235, into 2 main parts, accompanied by the release of much energy |
| Chain reaction | a self-sustaining reaction in which the products of one reaction event stimulate further reaction events |
| Critical Mass | The minimum mass of fissionable material in a reactor or nuclear bomb that will sustain a chain reaction |
| Nuclear fusion | the combining of nuclei of light atoms to form heavier nuclei, with the release of much energy |
| thermonuclear fusion | nuclear fusion produced by high temperature |
| Where does most of the radiation you encounter originate | Natural background radiation that originates in the earth and in space and was present long before we humans arrived |
| What are cosmic rays and where do they originate | They originate in teh sun and other stars and make up background radiation in space; high-energy particles or high-frequency electromagnetic radiation |
| How do the electric charges of alpha, beta, and gamma rays differ | Alpha: positive charge; Beta: negative charge; Gamma: no charge |