Nuclear Fission

The breakup of large nuclei into two nearly equal fragments is called nuclear fission.

It sometimes produces neutrons, protons or other nuclei. This is important in nuclear reactor and bombs, where neutrons emitted from one fission event cause other nuclei to fission, releasing more neutrons and so causing chain reaction. If this chain is controlled then you have a nuclear reactor whose heat can be used to boil water and generate electricity. If the chain is uncontrolled it causes a nuclear explosion.

Nuclear fission is a type of radioactivity.

During world war 2, a group under the leadership of Italian physicist Enrico Fermi showed that enough free neutrons are produced during the fission process to maintain a chain reaction. This development led to the construction of the atomic bomb. Later work resulted in the production of electric power from nuclear reactors.