Chapter 29: Nuclear Physics

Nuclear equations describe decay events through conservation laws, where both mass number and proton number remain constant across all transformations. Alpha decay reduces both nucleon count and atomic number, beta-minus decay increases proton number while preserving mass number, beta-plus decay decreases proton number, and gamma decay produces no change in nuclear composition. The mass-energy relationship established by Einstein reveals that the mass of any nucleus is less than the sum of its constituent nucleons, a difference called mass defect that converts to binding energy holding the nucleus together. Binding energy per nucleon serves as a quantitative measure of nuclear stability, with iron-56 representing the peak of this stability curve. Energy release in both fission and fusion processes results from differences in binding energy per nucleon between reactants and products. Radioactive decay exhibits two defining characteristics: it occurs spontaneously regardless of external conditions, and it proceeds randomly at the individual nucleus level, though statistical patterns emerge across large populations. The decay constant represents the probability of decay per unit time for any given nucleus, while activity quantifies the macroscopic decay rate measured in becquerels. Half-life provides an intuitive measure of decay timescale, inversely related to decay constant through logarithmic proportionality. The exponential decay formula describes how populations of unstable nuclei, their associated activities, and measured count rates all diminish over time according to predictable mathematical relationships. These interconnected concepts provide the framework for understanding nuclear phenomena from subatomic processes to practical applications in radiometric dating and nuclear energy production.