Discuss what determines the atomic number of an atom and the atomic mass. Introduce what an isotope is. Examine the isotope of uranium, U-235 and U-236. Analyze why 236 is not stable. Outline the fission reaction which spilts U-235 into a barium atom and a krypton atom, with the release of tremendous energy. Show how 3 neutrons are released for each U-225 split, causing a chain reaction.. Describe and examine an image of a nuclear reactor. Discuss the pros and cons of nuclear energy.