9-12

E7: Describe nuclear reactions, including fusion, fission, and decay, their occurrences in nature, and how they can be used by humans.

Curriculum Organizing Questions	What is a nuclear reaction? What is radioactive decay? Describe examples of natural radioactivity. Describe the different types of radioactive decay. What is the difference between nuclear fusion and fission? What are some positive and negative aspects of human use of radioactivity.
Elaboration	The nuclear forces that hold the nulceus of an atom together, at nuclear distances, are usually stronger than the electric forces that would make it fly apart. Nulcear reactions convert a fraction of the mass of interacting particles into energy, and they can release much greater amounts of energy than atomic interactions. Fission is the splitting of a large nucleus into smaller pieces. Fusion is the joining of two nuclei at extremely high temperatures and pressures, and is the process responsible for the energy of the sun and other stars. NSES p. 178 Radioactive istopes are unstable and undergo spontaneous nuclear reactions, emitting particles and/or wavelike radiation. The decay oif any one nucleus cannot be predicted, but a large numbber of identical nuclei decay at a predictable rate. This predictability can be used to estimate the age of materials that conrtain radioactive isotopes.NSES p. 178 Radioactivity has many uses other than generating energy, including in medicine, industry, and scientific research in many different fields.
Specific Ideas
Developmental & Instructional Implications	The focus of the "splitting-the-atom" story should be on the discovery of nuclear fission and its impact on world affairs. It is important not to overlook the science in this episode when considering the ethical and national-security considerati)ons associated with fission and fusion. Benchmarks p. 253
Examples

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