Outline why certain nuclei are stable. Define and discuss radioactivity as the decay of unstable nuclei. Introduce natural and induced radioactivity. List and discuss alpha and beta particles along with gamma rays. Discuss the nuclear strong force which prevents the nucleus from breaking apart due to electromagnetic repulsion. Elicit binding energy calculated by the difference between the energy of the assembled nucleus and the energy of the individual nucleons which comprise the nucleus. Discuss that it is always a negative number and is expressed by E=mc^2,