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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 longest-lived radioisotopes are 194 Hg with a half-life of 444 years, and 203 Hg with a half-life of 46.612 days. Most of the remaining 40 radioisotopes have half-lives that are less than a day. 199 Hg and 201 Hg are the most often studied NMR-active nuclei, having spin quantum numbers of 1/2 and 3/2 respectively.
The longest-lived radioisotopes are 205 Pb with a half-life of 17.3 million years and 202 Pb with a half-life of 52,500 years. A shorter-lived naturally occurring radioisotope, 210 Pb with a half-life of 22.2 years, is useful for studying the sedimentation chronology of environmental samples on time scales shorter than 100 years. [5]
The longest-lived radioisotopes are 135 Cs with a half-life of 1.33 million years, 137 Cs with a half-life of 30.1671 years and 134 Cs with a half-life of 2.0652 years. [6] All other isotopes have half-lives less than 2 weeks, most under an hour.
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 radioisotope is 18 F; it has a half-life of 109.734(8) min. All other fluorine isotopes have half-lives of less than a minute, and most of those less than a second. The least stable known isotope is 14 F, whose half-life is 500(60) yoctoseconds, [4] corresponding to a resonance width of 910(100) keV.
It is an extremely long-lived radioisotope, with a half-life of 1.06 × 10 11 years, although measurements have ranged from 1.05 × 10 11 to 1.17 × 10 11 years. [ 2 ] [ 3 ] It is mainly used in radiometric dating.