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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. [1]
Carbon-14 (and other isotopes generated by cosmic rays) and daughters of radioactive primordial elements, such as radium, polonium, etc. 41 of these have a half life of greater than one hour. Radioactive synthetic half-life ≥ 1.0 hour). Includes most useful radiotracers. 662 989 These 989 nuclides are listed in the article List of nuclides.
Radioactive isotopes ranging from 11 O to 28 O have also been characterized, all short-lived. The longest-lived radioisotope is 15 O with a half-life of 122.266(43) s, while the shortest-lived isotope is the unbound 11 O with a half-life of 198(12) yoctoseconds, though half-lives have not been measured for the unbound heavy isotopes 27 O and 28 ...
At least 3,300 nuclides have been experimentally characterized [1] (see List of radioactive nuclides by half-life for the nuclides with decay half-lives less than one hour). A nuclide is defined conventionally as an experimentally examined bound collection of protons and neutrons that either is stable or has an observed decay mode.
Rutherford applied the principle of a radioactive element's half-life in studies of age determination of rocks by measuring the decay period of radium to lead-206. Half-life is constant over the lifetime of an exponentially decaying quantity, and it is a characteristic unit for the exponential decay equation. The accompanying table shows the ...
The molar weight is 59.93. The half life T of 5.27 year corresponds to the activity A = N [ ln(2) / T ], where N is the number of atoms per mol, and T is the half-life. Taking care of the units the radiation power for 60 Co is 17.9 W/g Radiation power in W/g for several isotopes:
There are no stable nuclides with mass numbers 5 or 8. There are stable nuclides with all other mass numbers up to 208 with the exceptions of 147 and 151, which are represented by the very long-lived samarium-147 and europium-151. (Bismuth-209 was found to be radioactive in 2003, but with a half-life of 2.01 × 10 19 years.)
Natural iron (26 Fe) consists of four stable isotopes: 5.845% 54 Fe (possibly radioactive with half-life > 4.4 × 10 20 years), [4] 91.754% 56 Fe, 2.119% 57 Fe and 0.286% 58 Fe. There are 28 known radioisotopes and 8 nuclear isomers, the most stable of which are 60 Fe (half-life 2.6 million years) and 55 Fe (half-life 2.7 years).