Radioactivity Study Guide

Nuclear fission is a process where a large unstable nucleus splits into two or more smaller nuclei, often after absorbing a neutron. This splitting also releases additional neutrons, gamma radiation, and a significant amount of energy. The smaller nuclei formed during this process are known as fission products. Crucially, these fission products are almost always radioactive, meaning they are unstable and will undergo further radioactive decay. This radioactivity is a major concern in the management of nuclear waste, as these products remain hazardous for thousands of years, emitting radiation as they transform into more stable isotopes.

Nuclear fusion is a fundamental process in astrophysics and a potential future energy source. It involves the combining of two light atomic nuclei to form a single, heavier nucleus. During this process, a small amount of mass is converted into a considerable amount of energy. This mass-energy conversion aligns with Einstein's famous equation, E=mc². The total mass of the products after fusion is slightly less than the total mass of the original nuclei. This 'missing' mass is released as energy. Fusion reactions require extremely high temperatures and pressures to overcome the electrostatic repulsion between the positively charged nuclei, allowing them to get close enough for the strong nuclear force to bind them together. These conditions are naturally found in the cores of stars, such as our Sun, where fusion powers their immense energy output over billions of years, primarily by converting hydrogen into helium.