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List of nuclides
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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 (francium), 102 (nobelium) and 104 (rutherfordium). At least 3,300 nuclides have been experimentally characterized[1] - this page presently includes 987.
Introduction
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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 (meaning no decay mode is possible) 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 (either directly or by finding an excess of the daughter), the theoretical decay mode is given in parentheses, and "> (lifetime in years)" 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 (tellurium-128, barium-130). There are 35 of these (see these nuclides), of which 25 have half-lives longer than 1013 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 7×108 and 5×1011 years, which means they have undergone at least 0.5% depletion since the formation of the Solar System about 4.6×109 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.[a]
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 (radiogenic nuclides), such as radon-222. Others are the products of interactions with energetic cosmic rays (the cosmogenic nuclides), 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 (nucleogenic nuclides), and these are generally even less detectable.
Non-primordial nuclides may also be detected in the spectra of stars; technetium is well established,[3] 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 (or practically only) from deliberate or accidental release of artificial production, as fission products (from nuclear weapons or nuclear reactors), for industrial or medical uses, or otherwise.
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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.
- No. (number) column
- A running positive integer for reference, equal to the position in the tables. This number may change in the future, especially for nuclides with short lives, as better half-life estimates become available.
- Nuclide column
- Nuclide identifiers are given by their atomic mass number A and the symbol for the corresponding chemical element (corresponding to the unique proton number). In the cases that this is not the ground state, this is indicated by a m for metastable appended to the mass number; the conventional numbers are further appended to distinguish multiple metastable states but '1' is omitted if the others are much less stable.
- A, Z, N columns
- The total number of protons and neutrons together (A) and the separate numbers of protons (Z) and of neutrons (N).
- Energy column
- The column labeled "energy" denotes the energy equivalent of the mass of a neutron minus the mass per nucleon of this nuclide (so all nuclides have a positive value) in MeV, formally: mn − mnuclide / A, where A = Z + N is the mass number. Note that this means that a higher "energy" value actually means that the nuclide has a lower energy. The mass of the nuclide (in daltons) is A (mn − E / k) where E is the energy, mn is 1.008664916 Da and k = 931.49410242 the conversion factor between MeV and daltons.
- Half-life column
- The first column shows times in seconds; the second column in the more usual units (years, days, hours). As the first column is converted from the second, it is given enough digits to ensure consistent sorting.
- Entries starting with a ">" indicates that no decay has ever been observed, with experiments having established lower limits on the half-life. Such elements are considered stable unless decay is observed (establishing an actual estimate for the half-life). Half-lives are imprecise estimates and may be subject to significant revision. When shown to a smaller than usual number of significant figures, it is not known accurately enough to justify more.
- Decay mode column
α α decay β− β− decay β−β− double β− decay ε electron capture β+ β+ decay β+β+ double β+ decay SF spontaneous fission IT isomeric transition - Decay modes in parentheses are given for observationally stable nuclides (these and these); they are then those allowed to occur by energy (in the next column), but spontaneous fission (and cluster decay, which is never shown in this table) are neglected as they should never be observed for any of those. Nuclides with multiple significant decay modes have the probability of each decay mode in percent given, in small figures, in parentheses; those less than 0.05% are rounded to zero and omitted, and 100 (>99.5% of observed decays) is not used but replaced by bold unless the only other decays are SF or double beta, assumed to be minority decays if not listed first. If more than one of α, β−, β+/ε, IT is given without numbers or bold, one can assume no experimental data is available. Note that, by widely used convention, β+ (technically positron emission) includes ε, and conversely, if positron emission is energetically possible; the two are never separated on this page.
- Decay energy column
- Multiple values for (maximal) decay energy for each given decay mode, in respective order. The decay energy listed is for the specific nuclide only, not for the whole decay chain. It includes energy lost to neutrinos.
- Notes column
-
- CG
- Cosmogenic nuclide.
- DP
- Naturally occurring decay product (of thorium-232, uranium-238, or uranium-235), including products of neutron reactions other than fission.
- ESS
- Present in the early Solar System (first few million years), but extinct now as a primordial nuclide. Inherently overlaps with cosmogenic nuclides.
- FP
- Nuclear fission product [b] - may occur naturally from spontaneous fission.
- IM
- Industry or medically used radionuclide.[4]
Of the 701 non-primordial nuclides in the tables below, 101 have the label FP (99 true fission products), 65 IM, 32 DP, 24 CG, 13 ESS, and 7 both CG and ESS.
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Full list
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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. This should not be considered authoriative without consulting the original source (footnote) 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 (especially for alpha decay), but only the experiment's ability to measure it.
Primordial radioactive nuclides (half-life > 108 years)
Ordered by half-life, data selected from
- Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
Radionuclides with half-lives of 10,000 years to 108 years
Ordered by half-life. Some of these are known to have been present in the early Solar System (marked "ESS", meaning the first few million years of the Solar System's history) from an excess of their decay products.[29]
Radionuclides with half-lives of 10 years to 10,000 years
Ordered by half-life.
- Nubase value. However, a recent direct study: P. Adhikari; et al. (2025). "Direct Measurement of the Half-Life of 39Ar from 3.4 Years of Data with the DEAP-3600 Detector". The European Physical Journal C. 85 (7): 728. doi:10.1140/epjc/s10052-025-14289-5. found 302 years, a statistically significant discrepancy to be explained.
Radionuclide with unknown half-life
No decay has been observed, but not primordial so does not qualify as "observationally stable".
Radionuclides with half-lives of 1 day to 10 years
Ordered by half-life. The second half-life column in this table has been made unsortable, as the mixture of days and years will not sort properly. Resorting by half-life may be done no less by using the number or the half-life in seconds columns.
Radionuclides with half-lives of 1 hour to 1 day
Ordered by half-life.
- These superheavy isotopes have large statistical uncertainties in their half-lives because only a small number of atoms have been counted one at a time. They are given in their originally reported form with two significant figures, but would not deserve it by the standards applied to other isotopes. The actual uncertainty can be found through the isotope link.
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Radionuclides with half-lives less than 1 hour
The following is incomplete and out of date, but is the only such list we have.
See also
- Isotope geochemistry
- List of elements by stability of isotopes
- List of radioactive nuclides by half-life
- Monoisotopic element
- Mononuclidic element
- Primordial nuclide
- Radionuclide
- Stable nuclide
- Table of nuclides
Sources
List was begun from reference [41] and most more recent updates are reflected in reference.[42] These sources do not indicate whether some heavy isotopes were produced and observed, or only predicted from estimated data. None of the latter should appear here.
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Notes
- Two further nuclides, plutonium-244 and samarium-146, have half-lives just long enough (8.13×107 and 9.20×107 years[2]) that they could have survived from the formation of the Solar System and be present on Earth in trace quantities (having survived 56 and 50 half-lives). They might therefore be considered primordial, but fall short of the detection threshold in studies so far.[citation needed]
- Note that NUBASE2020 uses the tropical year to convert between years and other units of time, not the Gregorian year. The relationship between years and other time units in NUBASE2020 is as follows: 1 y = 365.2422 d = 31 556 926 s
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References
External links
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