Radioactive decay is a process by which an unstable atomic nucleus loses energy by radiation. This process involves alpha, beta, and gamma decay and is fundamental to nuclear physics.

Henri Becquerel discovered radioactivity in 1896 while working with phosphorescent materials. Marie and Pierre Curie's research expanded this knowledge, leading to the discovery of radium and polonium.

Radioactive decay is governed by quantum theory. It is impossible to predict when a specific atom will decay, but the decay rate can be expressed as a decay constant or half-life.

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Certain heavy nuclei decay in sequences called decay chains. Primordial radionuclides like uranium and thorium are remnants from before the formation of the Solar System.

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Most decay rates are not influenced by external conditions, but electron capture can be affected by chemical and environmental factors, with changes observed in isotopes like 7Be.

Radioactive decay is used in radiometric dating, nuclear medicine, and power generation. Isotopic labeling allows tracking chemical processes in organisms.

A common practice in nuclear medicine is the use of radioactive iodine to diagnose and treat thyroid cancer.

Ionizing radiation from decay poses health risks, including cancer. Historical use of radioactive substances in medicine led to increased safety regulations and radiation protection guidelines.