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Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha, beta, and gamma decay.
Atomic nuclei consist of protons and neutrons, ... This is the longest half-life directly measured for any unstable isotope; [4] only the half-life of tellurium-128 ...
All "stable" isotopes (stable by observation, not theory) are the ground states of nuclei, except for tantalum-180m, which is a nuclear isomer or excited state. The ground state, tantalum-180, is radioactive with half-life 8 hours; in contrast, the decay of the nuclear isomer is extremely strongly forbidden by spin-parity selection rules.
The island of stability is a hypothetical region in the top right cluster of nuclides that contains isotopes far more stable than other transuranic elements. There are no stable nuclides having an equal number of protons and neutrons in their nuclei with atomic number greater than 20 (i.e. calcium) as can be readily observed from the chart ...
Radioactive isotope table "lists ALL radioactive nuclei with a half-life greater than 1000 years", incorporated in the list above. The NUBASE2020 evaluation of nuclear physics properties F.G. Kondev et al. 2021 Chinese Phys. C 45 030001. The PDF of this article lists the half-lives of all known radioactives nuclides.
They have shorter half-lives than primordial radionuclides. They arise in the decay chain of the primordial isotopes thorium-232, uranium-238, and uranium-235. Examples include the natural isotopes of polonium and radium. Cosmogenic isotopes, such as carbon-14, are present because they are continually being formed in the atmosphere due to ...
This remarkable difference of nuclear binding energy between neighbouring nuclei, especially of odd-A isobars, has important consequences: unstable isotopes with a nonoptimal number of neutrons or protons decay by beta decay (including positron emission), electron capture, or other less common decay modes such as spontaneous fission and cluster ...
Some older sources give the final isotope as bismuth-209, but in 2003 it was discovered that it is very slightly radioactive, with a half-life of 2.01 × 10 19 years. [9] There are also non-transuranic decay chains of unstable isotopes of light elements, for example those of magnesium-28 and chlorine-39.