Most chemists pay little attention to the nucleus of an atom except to consider the number of protons it contains because that determines an element’s identity. However, in nuclear chemistry, the composition of the nucleus and the changes that occur there are very important. Applications of nuclear chemistry may be more widespread than you realize. Many people are aware of nuclear power plants and nuclear bombs, but nuclear chemistry also has applications ranging from smoke detectors to medicine, from the sterilization of food to the analysis of ancient artifacts. In this chapter, we will examine some of the basic concepts of nuclear chemistry and some of the nuclear reactions that are important in our everyday lives. 3.0: Prelude to Nuclear Chemistry A typical smoke detector contains an electric circuit that includes two metal plates about 1 cm apart. A battery in the circuit creates a voltage between the plates. Next to the plates is a small disk containing a tiny amount (∼0.0002 g) of the radioactive element americium (Am). The radioactivity of the americium ionizes the air between the plates, causing a tiny current to constantly flow between them. 3.1: Radioactivity Atoms are composed of subatomic particles—protons, neutrons, and electrons. Protons and neutrons are located in the nucleus and provide most of the mass of the atom, while electrons circle the nucleus in shells and subshells and account for an atom’s size. There are three main forms of radioactive emissions and are alpha particles, beta particles, and gamma rays. 3.2: Half-Life Natural radioactive processes are characterized by a half-life, the time it takes for half of the material to decay radioactively. The amount of material left over after a certain number of half-lives can be easily calculated. 3.3: Units of Radioactivity Radioactivity can be expressed in a variety of units, including rems, rads, and curies. 3.4: Uses of Radioactive Isotopes Radioactivity has several practical applications, including tracers, medical applications, dating once-living objects, and the preservation of food. 3.5: Nuclear Energy Nuclear energy comes from tiny mass changes in nuclei as radioactive processes occur. In fission, large nuclei break apart and release energy; in fusion, small nuclei merge together and release energy. 3.E: Nuclear Chemistry (Exercises) Select problems and solutions. 3.S: Nuclear Chemistry (Summary) Chapter summary