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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 ...
However, radioactive iodine is a disproportionate biohazard because the thyroid gland concentrates iodine. 129 I has a half-life nearly a billion times as long as its more hazardous sister isotope 131 I; therefore, with a shorter half-life and a higher decay energy, 131 I is approximately a billion times more radioactive than the longer-lived ...
Bismuth-209 (209 Bi) is an isotope of bismuth, with the longest known half-life of any radioisotope that undergoes α-decay (alpha decay).It has 83 protons and a magic number [2] of 126 neutrons, [2] and an atomic mass of 208.9803987 amu (atomic mass units).
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.
The longest lived, and most common, isotope of radium is 226 Ra with a half-life of 1600 years. 226 Ra occurs in the decay chain of 238 U (often referred to as the radium series). Radium has 34 known isotopes from 201 Ra to 234 Ra.