Nuclear Fission: A nuclear reaction in which the nucleus of an atom splits into smaller parts, often producing freeneutrons, lighter nuclei and photons (in the form of gamma rays). The process releases large amounts of energy, both as electromagnetic radiation and as kinetic energy of the resulting fragments.
Nuclear Fusion:
The welding together of two light nuclei to make a heaviernucleus, resulting in the liberation of nuclear energy. An example of this kind of nuclear reaction is the binding together of hydrogen nuclei in the core of the Sun to make helium. In larger, hotter stars, helium itself may fuse to produce heavierelements, a process which continues up the periodic table ofelements as far as iron. The fusion of ultra-stable iron nucleiactually absorbs energy rather than releasing it, and so iron does not easily fuse to create heavierelements.
