Nuclear Fusion & Fission
In 1938 two german chemists,Otto Hahn and Fritz Strassman were bombarding a sample of pure uranium (z=235) with nuetrons. they found in the sample, traces of barium and krypton as well as some other elements of medium mass. They and others realized that they had split the atom.
nuetron + Uranium(z=235) -> Barium(z=141) + Kryptonium(z=92)
Today we call this nuclear fission. If you add up the mass numbers of the particles involved in this reaction you will find that something is missing. Three nuetrons are olso given out.
nuetron + Uranium(z=235)->Barium(z=141) + Kryptonium(z=92)+ 3 nuetrons
Now not only is a tremedous amount of energy released during this process(1 000 000 times more per atom than in a chemical reaction)but if the three nuetrons were able to split three more atoms and produce more energy and nine nuetrons a chain reaction might begin. If the uranium sample were too small most nuetrons would escape but if it were big enough(greater than the critical mass the nuetrons would undergo futher collusions. In each fission a little mass is changed to energy in accordance with Einstein's fomula: E = mc2.