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This is a list of radioactive nuclides (sometimes also called isotopes), ordered by half-life from shortest to longest, in seconds, minutes, hours, days and years. Current methods make it difficult to measure half-lives between approximately 10 −19 and 10 −10 seconds.
The longest-lived radioisotope is 14 C, with a half-life of 5.70(3) × 10 3 years. This is also the only carbon radioisotope found in nature, as trace quantities are formed cosmogenically by the reaction 14 N + n → 14 C + 1 H. The most stable artificial radioisotope is 11 C, which has a half-life of 20.3402(53) min. All other radioisotopes ...
The definition of "longest-living" used in this article considers only the observed or estimated length of an individual organism's natural lifespan – that is, the duration of time between its birth or conception, or the earliest emergence of its identity as an individual organism, and its death – and does not consider other conceivable ...
Bismuth-209 was long thought to have the heaviest stable nucleus of any element, but in 2003, a research team at the Institut d’Astrophysique Spatiale in Orsay, France, discovered that 209 Bi undergoes alpha decay with a half-life of 20.1 exayears (2.01×10 19, or 20.1 quintillion years), [3] [4] over 10 9 times longer than the estimated age of the universe. [5]
There are 40 known isotopes of iodine (53 I) from 108 I to 147 I; all undergo radioactive decay except 127 I, which is stable. Iodine is thus a monoisotopic element.. Its longest-lived radioactive isotope, 129 I, has a half-life of 16.14 million years, which is far too short for it to exist as a primordial nuclide.
The next group is the primordial radioactive nuclides. These have been measured to be radioactive, or decay products have been identified in natural samples (tellurium-128, barium-130). There are 35 of these (see these nuclides), of which 25 have half-lives longer than 10 13 years. With most of these 25, decay is difficult to observe and for ...
The longest-lived of these is 133 Ba, which has a half-life of 10.51 years. All other radioisotopes have half-lives shorter than two weeks. The longest-lived isomer is 133m Ba, which has a half-life of 38.9 hours. The shorter-lived 137m Ba (half-life 2.55 minutes) arises as the decay product of the common fission product caesium-137.
The longest-lived artificial radioisotope of tellurium is 121 Te with a half-life of about 19 days. Several nuclear isomers have longer half-lives, the longest being 121m Te with a half-life of 154 days. The very-long-lived radioisotopes 128 Te and 130 Te are the two most common isotopes of tellurium.