List of nuclides
This list of nuclides shows observed nuclides that either are stable or, if radioactive, have half-lives longer than one hour. This includes isotopes of the first 105 elements, except for 87, 102 and 104. More than 5,000 nuclides have been experimentally characterized, including isomers, of which this page presently includes 987.
Introduction
There are presently 251 known stable nuclides. Many of these in theory could decay through spontaneous fission, alpha decay, double beta decay, etc. with a very long half-life, but this has not yet been observed. Thus, the number of stable nuclides is subject to change if some of these 251 have radioactive decay observed in the future. In this article, the "stable" nuclides are divided into three tables: one for nuclides that are theoretically stable except to spontaneous fission, which is not considered plausible in this mass range; one for nuclides that can theoretically undergo forms of decay other than spontaneous fission but have no published lower bound on lifetime from experimental evaluations; and one for nuclides that can theoretically decay and have been examined without detecting any decay, allowing a lower bound to be published. In this last table, where a decay has been predicted theoretically but never observed experimentally, the theoretical decay mode is given in parentheses, and "> " is shown in the half-life column to show this lower limit in scientific notation. Such nuclides are considered to be "stable", also called "observationally stable" indicating the tentative nature of the conclusion, until some decay has been observed. For example, tellurium-123 was reported to be radioactive, but the same experimental group later retracted this report, and it is again listed as stable.The next group is the primordial radioactive nuclides. These have been measured to be radioactive, or decay products have been identified in natural samples. There are 35 of these, of which 25 have half-lives longer than years. For most of these 25, decay is difficult to observe, and for most purposes they can be regarded as effectively stable. Bismuth-209 is notable as it is the only naturally occurring isotope of an element long considered stable. The other 10, platinum-190, samarium-147, lanthanum-138, rubidium-87, rhenium-187, lutetium-176, thorium-232, uranium-238, potassium-40, and uranium-235, have half-lives between and years, which means they have undergone at least 0.5% depletion since the formation of the Solar System about years ago, but still exist on Earth in significant quantities. They are the primary source of radiogenic heating and radioactive decay products. Together, there are a total of 286 primordial nuclides.
The list then covers the other radionuclides with half-lives longer than 1 hour, split into several tables in order of successively shorter lifetimes.
Some nuclides that have half-lives too short to be primordial can be detected in nature as a result of later production by natural processes, mostly in trace amounts. These include radionuclides occurring in the decay chains of primordial uranium and thorium, such as radon-222. Others are the products of interactions with energetic cosmic rays, such as carbon-14. This gives a total of about 350 naturally occurring nuclides, some of which are difficult to detect. Other nuclides may be occasionally produced naturally by rare cosmogenic interactions or as a result of other natural nuclear reactions, and these are generally even less detectable.
Non-primordial nuclides may also be detected in the spectra of stars; technetium is well established, and others have been claimed. The remaining nuclides are known solely from artificial nuclear transmutations. Some, such as caesium-137 and krypton-85, are detected in the environment, but only from deliberate or accidental release of artificial production, as fission products, for industrial or medical uses, or otherwise.
List legend
Each group of radionuclides, starting with the longest-lived primordial radionuclides, is sorted by decreasing half-life, but the tables are sortable by other columns. All columns sort by usual lexicographical order; in the case of the nuclide column this gives order on the mass number A.----
Of the 701 non-primordial nuclides in the tables below, 101 have the label FP, 65 IM, 32 DP, 24 CG, 13 ESS, and 7 both CG and ESS.
Full list
The tables are based now on the standard reference NUBASE2020 and its companion, based on the same data, AME2020. All observational data not otherwise cited should be found in those sources, or calculated from them, and only observed data, not theoretical extrapolations, should be present in these tables.Theoretically stable nuclides
These are the theoretically stable nuclides, ordered by "energy".Observationally stable nuclides having theoretical decay modes other than spontaneous fission (no lower bounds)
Ordered by "energy".Observationally stable nuclides having theoretical decay modes other than spontaneous fission, for which those decays have experimental lower bounds
Ordered by the given lower bound on half-life. These should not be considered authoritative without consulting the original source as exactly what was measured and how are not reflected here, and some of the values may be misinterpretations. Further, in all cases, this is not an indicator of the probable half-life, which may be much longer, but only the experiment's ability to measure it.Primordial radioactive nuclides (half-life > 108 years)
Ordered by half-life.Radionuclides with half-lives of 104 years to 108 years
Ordered by half-life. Some of these are known to have been present in the early Solar System from an excess of their decay products.Radionuclides with half-lives of 10 years to 104 years
Ordered by half-life.Radionuclide with unknown half-life
No decay has been observed, but not primordial so does not qualify as "observationally stable".| No. | Nuclide | Z | N | Energy | Half-life | Half-life | Decay modes | Notes |
| 380 | 248Bk | 97 | 151 | > | > 9 y | α, β−, β+ |