Radioactivity

Radioactivity, also known as radioactive decay, describes the process of spontaneous breakdown of unstable (or radioactive) nuclides, with the formation of daughter nuclei and release of subatomic particles and/or gamma radiation. A single decay (a.k.a. disintegration) refers to the degradation of one nuclide into another. 

Modes of decay

• alpha decay
• beta decay
• electron capture
• spontaneous fission
• isomeric transition
  • gamma (γ) ray emission (gamma decay)
  • internal conversion

Radioactive decay is a stochastic process, i.e. it is probabilistic, and it is impossible to foresee which specific nuclei will decay. Nevertheless, it can be predicted with a high degree of confidence the proportion of any sample of radioactive atoms that will decay in a specified period of time.

History and etymology

Henri Becquerel (1852-1908) discovered radioactivity in 1896 when studying potassium uranyl sulfate ². Further early advances were made by wife and husband, Marie Skłodowska Curie (1867-1934) and Pierre Curie (1859–1906), who were co-awarded the Nobel Prize in Physics with Becquerel in 1903. It was Marie Curie who coined the term radioactivity ⁴.