Alpha decay is a variant of radioactive decay whereby an atomic nucleus emits an alpha particle and becomes a nucleus with four units fewer mass number and two units fewer atomic number.
Beta decay or beta emission is a process by which an unstable nucleus emits a beta particle (an electron or positron) to compensate for the ratio of neutrons to protons in the atomic nucleus. This disintegration violates parity.
Nuclear fission is the splitting of a nucleus into lighter nuclei, plus some by-products such as free neutrons, photons (usually gamma rays) and other fragments of the nucleus such as alpha (helium nuclei) and beta (high-energy electrons and positrons) particles plus a large amount of energy.
This simulation is intended to show the principle of a nuclear fusion reaction. See what happens when bombarding uranium atoms, depending on the concentration. When considering this simulation, note that the proportions of the model presented may not match reality, that the nucleus has been exaggerated and drawn large, and that the electrons around the nucleus are not shown.