As we have progressed through this text, our focus has been on chemical reactions, specifically reactions in which electrons play a dominant role. In this chapter we consider nuclear reactions, changes in matter originating in the nucleus of an atom. When nuclei change spontaneously, emitting radiation, they are said to be radioactive. As we will see, there are other kinds of nuclear reactions as well. Nuclear chemistry is the study of nuclear reactions and their uses in chemistry.
Nuclear chemistry affects our lives in a variety of ways. Radioactive elements are widely used in medicine as diagnostic tools and as a means of treatment, especially for cancer (Figure 21.1). They are also used to help determine the mechanisms of chemical reactions, to trace the movement of atoms in biological systems, and to date important historical artifacts. Nuclear reactions are used both to generate electricity and to create weapons of massive destruction.
Although the growth of commercial nuclear power has slowed in the United States, it still accounts for about 20% of the total electricity generated. The use of nuclear energy and the disposal of nuclear wastes, however, are extremely controversial social and political issues. Because these topics evoke such a strong emotional reaction, it is often difficult to sift fact from opinion to make rational decisions. It is imperative, therefore, that we have some understanding of nuclear reactions and the uses of radioactive substances.