1. High School Physical Science Week 11 Radioactivity

2. Discovery Henri Becquerel discovered radioactivity while trying to study X rays. Radioactivity is the process by which a nucleus gives off nuclear radiation.

3. Chemical Rxns vs. Nuclear Rxns Chemical Reactions: Atoms never change identity. Electrons are involved in bonds forming and breaking. Small changes in energy. No measureable change in mass. Rate of the reaction dependent on temperature, concentration, catalysts, and nature of the substance. Nuclear Reactions Atoms of one element change into atoms of another. Protons and neutrons are involved. Large changes of energy. Measureable changes in mass. Reaction rates are affected by the number of nuclei ( + and n)

4. Particles and Rays An alpha particle is composed of two protons and two neutrons. A beta particle can be an electron or a positron. Gamma rays are a form of light with very high energy. Gamma rays penetrate matter better than alpha or beta particles do. Beta particles penetrate matter better than alpha particles do.

5. Half Life and Uses Nuclear radiation can damage living and nonliving matter. Half-life is the amount of time it takes for one- half of the nuclei of a radioactive isotope to decay. The age of some objects can be determined using half-lives. Uses of radioactive materials include detecting defects in materials, sterilizing products, diagnosing illness, and generating electrical energy.

6. Fusion In nuclear fusion, two or more nuclei combine to form a larger nucleus. Nuclear fusion cannot yet be used as an energy source, but plentiful fuel and little waste are advantages of fusion.

7. Fission In nuclear fission, a massive nucleus breaks into two nuclei. Nuclear fission is used in power plants to generate electrical energy. A limited fuel supply and radioactive waste products are disadvantages of fission.

8. Fusion vs Fission Fusion 2 nuclei combine to produce a nucleus of heavier mass Releases more energy than required to initiate the rxn. Advantages Fuel is inexpensive, readily available Products of fusion are not radioactive Releases more energy than fission Disadvantages High temps required No container available to maintain reactants at this temp Fission The splitting of a nucleus into smaller fragments Reactions have to be slow so the chain reaction will continue. Must have critical mass( Amount to start the reaction)