Nuclear Fission:

Splitting the Atom You know  that atoms are made up of a nucleus and electrons moving around the nucleus, and the nucleus  is made up of protons and neutrons. The principal  actor in  the fission drama is the uranium atom. The nucleus of  the Uranium 238 atom has 92 protons and  146 neutrons. About one atom  in  140 atoms of uranium has  143 neutrons in  its nucleus. lt  is called Uranium 235. It  is the Uranium 235 that  is mostly used  to provide fuel for nuclear furneces. Before the Second World War, two German scientists discovered that if  neutrons were shot at the nuclei of Uranium 235, the nuclei split into two and produced other neutrons to repeat the process. This is called nuclear fission.