Radioactivity, or radioactive decay, is the process by which an unstable nucleus gives off energy as radiation as it seeks a more stable state. In alpha decay an alpha particle is emitted, which is a helium nucleus. In beta decay a high-energy electron, called a beta particle, is emitted from the nucleus rather than from the electron cloud. In gamma decay, a gamma ray is emitted, which is electromagnetic radiation with the shortest known wavelength. Any isotope that emits radiation is called a radioisotope. Radioisotopes each have a half-life (t1⁄2), the time it takes for half of a sample of the isotope to decay. Half-life can be used in radiometric dating, that is, determining the age of a substance based on its isotopic composition. The radiation emitted during radioactive decay can be harmful to organic tissue. The biological effects of radiation can be categorized as deterministic or stochastic, acute or latent, and somatic or genetic. Instruments used to measure radiation include Geiger counters, scintillation counters, and dosimeters. Although radiation is dangerous to living organisms, radioisotopes have many practical applications, including nuclear medicine, industrial and research uses, and the generation of electricity in nuclear power plants.
At A Glance
Radioactive decay happens when an unstable nucleus gives off energy as radiation. Alpha, beta, and gamma decay are the three main types of radioactive decay.
- Ionizing radiation, which can form ions when it strikes a molecule, can cause biological effects that are frequently harmful to organisms. Instruments to detect ionizing radiation include Geiger counters, scintillation counters, and dosimeters.
Radioisotopes have many uses, including those in nuclear medicine, as radiolabels in research and industry, in gamma radiography (testing pipelines and infrastructure), and in generating electricity in nuclear power plants.