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{{more citations needed|date=December 2018}}
{{more citations needed|date=December 2018}}
[[File:Table isotopes en.svg|upright=1.4|thumb|Graph of nuclides (isotopes) by type of decay. Orange and blue nuclides are unstable, with the black squares between these regions representing stable nuclides. The continuous line passing below most of the nuclides comprises the positions on the graph of the (mostly hypothetical) nuclides for which proton number would be the same as neutron number. The graph reflects the fact that elements with more than 20 protons either have more neutrons than protons or are unstable.]]
[[File:Table isotopes en.svg|upright=1.4|thumb|Graph of nuclides (isotopes) by type of decay. Orange and blue nuclides are unstable, with the black squares between these regions representing stable nuclides. The continuous line passing below most of the nuclides comprises the positions on the graph of the (mostly hypothetical) nuclides for which proton number would be the same as neutron number. The graph reflects the fact that elements with more than 20 protons either have more neutrons than protons or are unstable.]]
'''Stable nuclides''' are [[nuclide]]s that are not radioactive and so (unlike [[radionuclide]]s) do not spontaneously undergo [[radioactive decay]].<ref>{{cite web |title=DOE explains ... Isotopes |url=https://www.energy.gov/science/doe-explainsisotopes |publisher=Department of Energy, United States |access-date=11 January 2023 |archive-url=https://web.archive.org/web/20220414025223/https://www.energy.gov/science/doe-explainsisotopes |archive-date=14 April 2022}}</ref> When such nuclides are referred to in relation to specific elements, they are usually termed '''stable isotopes'''.
'''Stable nuclides''' are [[Isotope|isotopes]] of a [[chemical element]] whose [[Nucleon|nucleons]] are in a configuration that does not permit them the surplus energy required to produce a radioactive emission. The [[Atomic nucleus|nuclei]] of such isotopes are not radioactive and unlike [[radionuclide]]s do not spontaneously undergo [[radioactive decay]].<ref>{{cite web |title=DOE explains ... Isotopes |url=https://www.energy.gov/science/doe-explainsisotopes |publisher=Department of Energy, United States |access-date=11 January 2023 |archive-url=https://web.archive.org/web/20220414025223/https://www.energy.gov/science/doe-explainsisotopes |archive-date=14 April 2022}}</ref> When these nuclides are referred to in relation to specific elements they are usually called that element's '''stable isotopes'''.


The 80 elements with one or more stable isotopes comprise a total of 251 nuclides that have not been known to decay using current equipment (see list at the end of this article). Of these 80 elements, 26 have only one stable isotope; they are thus termed [[monoisotopic element|monoisotopic]]. The rest have more than one stable isotope. [[Tin]] has ten stable isotopes, the largest number of stable isotopes known for an element.
The 80 elements with one or more stable isotopes comprise a total of 251 nuclides that have not been shown to decay using current equipment. Of these 80 elements, 26 have only one stable isotope and are called [[monoisotopic element|monoisotopic]]. The other 56 have more than one stable isotope. [[Tin]] has ten stable isotopes, the largest number of any element.


== Definition of stability, and naturally occurring nuclides ==
== Definition of stability, and naturally occurring nuclides ==


Most naturally occurring [[nuclide]]s are stable (about 251; see list at the end of this article), and about 35 more (total of 286) are known to be radioactive with sufficiently long half-lives (also known) to occur primordially. If the half-life of a [[nuclide]] is comparable to, or greater than, the Earth's age (4.5 billion years), a significant amount will have survived since the [[Formation and evolution of the Solar System|formation of the Solar System]], and then is said to be [[Primordial nuclide|primordial]]. It will then contribute in that way to the natural isotopic composition of a chemical element. Primordially present radioisotopes are easily detected with half-lives as short as 700 million years (e.g., [[uranium-235|<sup>235</sup>U]]). This is the present limit of detection,{{citation needed|date=February 2021}} as shorter-lived nuclides have not yet been detected undisputedly in nature except when recently produced, such as decay products or cosmic ray spallation.
Most naturally occurring [[nuclide]]s are stable (about 251; see list at the end of this article), and about 35 more (total of 286) are known to be radioactive with long enough half-lives (also known) to occur primordially. If the half-life of a [[nuclide]] is comparable to, or greater than, the Earth's age (4.5 billion years), a significant amount will have survived since the [[Formation and evolution of the Solar System|formation of the Solar System]], and then is said to be [[Primordial nuclide|primordial]]. It will then contribute in that way to the natural isotopic composition of a chemical element. Primordial radioisotopes are easily detected with half-lives as short as 700 million years (e.g., [[uranium-235|{{sup|235}}U]]). This is the present limit of detection,{{citation needed|date=February 2021}} as shorter-lived nuclides have not yet been detected undisputedly in nature except when recently produced, such as decay products or cosmic ray spallation.


Many naturally occurring radioisotopes (another 53 or so, for a total of about 339) exhibit still shorter half-lives than 700 million years, but they are made freshly, as daughter products of decay processes of primordial nuclides (for example, radium from uranium) or from ongoing energetic reactions, such as [[cosmogenic nuclide]]s produced by present bombardment of Earth by [[cosmic rays]] (for example, <sup>14</sup>C made from nitrogen).
Many naturally occurring radioisotopes (another 53 or so, for a total of about 339) exhibit still shorter half-lives than 700 million years, but they are made freshly, as daughter products of decay processes of primordial nuclides (for example, radium from uranium), or from ongoing energetic reactions, such as [[cosmogenic nuclide]]s produced by present bombardment of Earth by [[cosmic rays]] (for example, {{sup|14}}C made from nitrogen).


Some isotopes that are classed as stable (i.e. no radioactivity has been observed for them) are predicted to have extremely long half-lives (sometimes as high as 10<sup>18</sup> years or more).<ref name="bellidecay">{{cite journal |last1=Belli |first1=P. |last2=Bernabei |first2=R. |last3=Danevich |first3=F. A. |last4=Incicchitti |first4=A. |last5=Tretyak |first5=V. I. |display-authors=3 |title=Experimental searches for rare alpha and beta decays |journal=European Physical Journal A |date=2019 |volume=55 |issue=8 |pages=140–1–140–7 |doi=10.1140/epja/i2019-12823-2 |issn=1434-601X |arxiv=1908.11458|bibcode=2019EPJA...55..140B |s2cid=201664098 }}</ref> If the predicted half-life falls into an experimentally accessible range, such isotopes have a chance to move from the list of stable nuclides to the radioactive category, once their activity is observed. For example, <sup>209</sup>Bi and <sup>180</sup>W were formerly classed as stable, but were found to be [[alpha particle|alpha]]-active in 2003. However, such nuclides do not change their status as primordial when they are found to be radioactive.
Some isotopes that are classed as stable (i.e. no radioactivity has been observed for them) are predicted to have extremely long half-lives (sometimes 10{{sup|18}} years or more).<ref name="bellidecay">{{cite journal |last1=Belli |first1=P. |last2=Bernabei |first2=R. |last3=Danevich |first3=F. A. |last4=Incicchitti |first4=A. |last5=Tretyak |first5=V. I. |display-authors=3 |title=Experimental searches for rare alpha and beta decays |journal=European Physical Journal A |date=2019 |volume=55 |issue=8 |pages=140–1–140–7 |doi=10.1140/epja/i2019-12823-2 |issn=1434-601X |arxiv=1908.11458|bibcode=2019EPJA...55..140B |s2cid=201664098 }}</ref> If the predicted half-life falls into an experimentally accessible range, such isotopes have a chance to move from the list of stable nuclides to the radioactive category, once their activity is observed. For example, {{sup|209}}Bi and {{sup|180}}W were formerly classed as stable, but were found to be [[alpha particle|alpha]]-active in 2003. However, such nuclides do not change their status as primordial when they are found to be radioactive.


Most stable isotopes on Earth are believed to have been formed in processes of [[nucleosynthesis]], either in the [[Big Bang]], or in generations of stars that preceded the [[formation of the Solar System]]. However, some stable isotopes also show abundance variations in the earth as a result of decay from long-lived radioactive nuclides. These decay-products are termed [[radiogenic]] isotopes, in order to distinguish them from the much larger group of 'non-radiogenic' isotopes.
Most stable isotopes on Earth are believed to have been formed in processes of [[nucleosynthesis]], either in the [[Big Bang]], or in generations of stars that preceded the [[formation of the Solar System]]. However, some stable isotopes also show abundance variations in the earth as a result of decay from long-lived radioactive nuclides. These decay-products are termed [[radiogenic]] isotopes, in order to distinguish them from the much larger group of 'non-radiogenic' isotopes.
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{{see also|List of elements by stability of isotopes|List of nuclides|Beta-decay stable isobars}}
{{see also|List of elements by stability of isotopes|List of nuclides|Beta-decay stable isobars}}


Of the known chemical elements, 80 elements have at least one stable nuclide. These comprise the first 82 elements from [[hydrogen]] to [[lead]], with the two exceptions, [[technetium]] (element 43) and [[promethium]] (element 61), that do not have any stable nuclides. As of 2023, there were a total of 251 known "stable" nuclides. In this definition, "stable" means a nuclide that has never been observed to decay against the natural background. Thus, these elements have half-lives too long to be measured by any means, direct or indirect.
Of the known chemical elements, 80 elements have at least one stable nuclide. These comprise the first 82 elements from [[hydrogen]] to [[lead]], with the two exceptions, [[technetium]] (element 43) and [[promethium]] (element 61), that do not have any stable nuclides. As of 2024, there are total of 251 known "stable" nuclides. In this definition, "stable" means a nuclide that has never been observed to decay against the natural background. Thus, these elements have half-lives too long to be measured by any means, direct or indirect.


Stable isotopes:
Stable isotopes:
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These last 26 are thus called ''[[monoisotopic element]]s''.<ref name=nuclidetable>{{cite web|url=http://www.nndc.bnl.gov/chart/|title=Interactive Chart of Nuclides|publisher=Brook haven National Laboratory|author=Sonzogni, Alejandro|location=National Nuclear Data Center|access-date=2008-06-06|archive-date=2018-10-10|archive-url=https://web.archive.org/web/20181010070007/http://www.nndc.bnl.gov/chart/|url-status=dead}}</ref> The mean number of stable isotopes for elements which have at least one stable isotope is 251/80 = 3.1375.
These last 26 are thus called ''[[monoisotopic element]]s''.<ref name=nuclidetable>{{cite web|url=http://www.nndc.bnl.gov/chart/|title=Interactive Chart of Nuclides|publisher=Brook haven National Laboratory|author=Sonzogni, Alejandro|location=National Nuclear Data Center|access-date=2008-06-06|archive-date=2018-10-10|archive-url=https://web.archive.org/web/20181010070007/http://www.nndc.bnl.gov/chart/|url-status=dead}}</ref> The mean number of stable isotopes for elements which have at least one stable isotope is 251/80 = 3.1375.


=== Physical magic numbers and odd and even proton and neutron count {{anchor|Proton and neutron count parity|Odd and even proton and neutron count}}===
=== Physical magic numbers and odd and even proton and neutron count<span class="anchor" id="Proton and neutron count parity"></span><span class="anchor" id="Odd and even proton and neutron count"></span> ===
<!-- No article links to this anchor. -->
{{See also|Even and odd atomic nuclei}}
{{See also|Even and odd atomic nuclei}}


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Just as in the case of electrons, which have the lowest energy state when they occur in pairs in a given orbital, nucleons (both protons and neutrons) exhibit a lower energy state when their number is even, rather than odd. This stability tends to prevent beta decay (in two steps) of many even–even nuclides into another even–even nuclide of the same mass number but lower energy (and of course with two more protons and two fewer neutrons), because decay proceeding one step at a time would have to pass through an odd–odd nuclide of higher energy. Such nuclei thus instead undergo [[double beta decay]] (or are theorized to do so) with half-lives several orders of magnitude larger than the [[age of the universe]]. This makes for a larger number of stable even–even nuclides, which account for 150 of the 251 total. Stable even–even nuclides number as many as three [[isobar (nuclide)|isobars]] for some mass numbers, and up to seven isotopes for some atomic numbers.
Just as in the case of electrons, which have the lowest energy state when they occur in pairs in a given orbital, nucleons (both protons and neutrons) exhibit a lower energy state when their number is even, rather than odd. This stability tends to prevent beta decay (in two steps) of many even–even nuclides into another even–even nuclide of the same mass number but lower energy (and of course with two more protons and two fewer neutrons), because decay proceeding one step at a time would have to pass through an odd–odd nuclide of higher energy. Such nuclei thus instead undergo [[double beta decay]] (or are theorized to do so) with half-lives several orders of magnitude larger than the [[age of the universe]]. This makes for a larger number of stable even–even nuclides, which account for 150 of the 251 total. Stable even–even nuclides number as many as three [[isobar (nuclide)|isobars]] for some mass numbers, and up to seven isotopes for some atomic numbers.


Conversely, of the 251 known stable nuclides, only five have both an odd number of protons ''and'' odd number of neutrons: hydrogen-2 ([[deuterium]]), [[lithium-6]], [[boron-10]], [[nitrogen-14]], and [[tantalum-180m]]. Also, only four naturally occurring, radioactive odd–odd nuclides have a half-life over a billion years: [[potassium-40]], [[vanadium-50]], [[lanthanum-138]], and [[lutetium-176]]. Odd–odd [[primordial nuclide]]s are rare because most odd–odd nuclei are unstable with respect to [[beta decay]], because the decay products are even–even, and are therefore more strongly bound, due to [[Semi-empirical mass formula#Pairing term|nuclear pairing effects]].<ref>{{cite book| last=Various| editor=Lide, David R.| year=2002| title=Handbook of Chemistry & Physics| edition=88th| publisher=CRC| url=http://www.hbcpnetbase.com/| access-date=2008-05-23| isbn=978-0-8493-0486-6| oclc=179976746| archive-date=2017-07-24| archive-url=https://web.archive.org/web/20170724011402/http://www.hbcpnetbase.com/| url-status=dead}}</ref>
Conversely, of the 251 known stable nuclides, only five have both an odd number of protons ''and'' odd number of neutrons: hydrogen-2 ([[deuterium]]), [[lithium-6]], [[boron-10]], [[nitrogen-14]], and [[tantalum-180m]]. Also, only four naturally occurring, radioactive odd–odd nuclides have a half-life >10{{sup|9}} years: [[potassium-40]], [[vanadium-50]], [[lanthanum-138]], and [[lutetium-176]]. Odd–odd [[primordial nuclide]]s are rare because most odd–odd nuclei [[beta-decay]], because the decay products are even–even, and are therefore more strongly bound, due to [[Semi-empirical mass formula#Pairing term|nuclear pairing effects]].<ref>{{cite book| last=Various| editor=Lide, David R.| year=2002| title=Handbook of Chemistry & Physics| edition=88th| publisher=CRC| url=http://www.hbcpnetbase.com/| access-date=2008-05-23| isbn=978-0-8493-0486-6| oclc=179976746| archive-date=2017-07-24| archive-url=https://web.archive.org/web/20170724011402/http://www.hbcpnetbase.com/| url-status=dead}}</ref>


Yet another effect of the instability of an odd number of either type of nucleons is that odd-numbered elements tend to have fewer stable isotopes. Of the 26 [[monoisotopic element]]s (those with only a single stable isotope), all but one have an odd atomic number, and all but one has an even number of neutrons—the single exception to both rules being beryllium.
Yet another effect of the instability of an odd number of either type of nucleon is that odd-numbered elements tend to have fewer stable isotopes. Of the 26 [[monoisotopic element]]s (those with only one stable isotope), all but one have an odd atomic number, and all but one has an even number of neutrons: the single exception to both rules is [[beryllium]].


The end of the stable elements in the periodic table occurs after [[lead]], largely due to the fact that nuclei with 128 neutrons—two neutrons above the [[magic number (physics)|magic number]] 126—are extraordinarily unstable and almost immediately shed alpha particles.<ref name=n126sig>{{cite journal |last=Kelkar |first=N. G. |last2=Nowakowski |first2=M. |date=2016 |title=Signature of the ''N''&nbsp;{{=}}&nbsp;126 shell closure in dwell times of alpha-particle tunneling |journal=Journal of Physics G: Nuclear and Particle Physics |volume=43 |number=105102 |doi=10.1088/0954-3899/43/10/105102 |arxiv=1610.02069}}</ref> This also contributes to the very short half-lives of [[astatine]], [[radon]], and [[francium]] relative to heavier elements. A similar phenomenon occurs to a much lesser extent with 84 neutrons—two neutrons above the magic number 82—where various isotopes of elements in the [[lanthanide series]] exhibit alpha decay.
The end of the stable elements occurs after [[lead]], largely because nuclei with 128 neutrons—two neutrons above the [[magic number (physics)|magic number]] 126—are extraordinarily unstable and almost immediately alpha-decay.<ref name=n126sig>{{cite journal |last1=Kelkar |first1=N. G. |last2=Nowakowski |first2=M. |date=2016 |title=Signature of the ''N''&nbsp;{{=}}&nbsp;126 shell closure in dwell times of alpha-particle tunneling |journal=Journal of Physics G: Nuclear and Particle Physics |volume=43 |number=105102 |doi=10.1088/0954-3899/43/10/105102 |arxiv=1610.02069|bibcode=2016JPhG...43j5102K }}</ref> This contributes to the very short half-lives of [[astatine]], [[radon]], and [[francium]]. A similar phenomenon occurs to a much lesser extent with 84 neutrons—two neutrons above the magic number 82—where various isotopes of [[lanthanide]] elements alpha-decay.


=== Nuclear isomers, including a "stable" one ===
=== Nuclear isomers, including a "stable" one ===
The count of 251 known stable nuclides includes tantalum-180m, since even though its decay and instability is automatically implied by its notation of "metastable", this has still not yet been observed. All "stable" isotopes (stable by observation, not theory) are the ground states of nuclei, with the exception of tantalum-180m, which is a [[nuclear isomer]] or excited state. The ground state of this particular nucleus, tantalum-180, is radioactive with a comparatively short half-life of 8 hours; in contrast, the decay of the excited nuclear isomer is extremely strongly forbidden by spin-parity selection rules. It has been reported experimentally by direct observation that the half-life of <sup>180m</sup>Ta to gamma decay must be more than 10<sup>15</sup> years. Other possible modes of <sup>180m</sup>Ta decay (beta decay, electron capture, and alpha decay) have also never been observed.
The 251 known stable nuclides include tantalum-180m, since even though its decay is automatically implied by its being "metastable", this has not been observed. All "stable" isotopes (stable by observation, not theory) are the ground states of nuclei, except for tantalum-180m, which is a [[nuclear isomer]] or excited state. The ground state, tantalum-180, is radioactive with half-life 8 hours; in contrast, the decay of the nuclear isomer is extremely strongly forbidden by spin-parity selection rules. It has been reported by direct observation that the half-life of {{sup|180m}}Ta to gamma decay must be >10{{sup|15}} years. Other possible modes of {{sup|180m}}Ta decay (beta decay, electron capture, and alpha decay) have also never been observed.


[[File:Binding energy curve - common isotopes.svg|thumb|upright=1.2|Binding energy per nucleon of common isotopes.]]
[[File:Binding energy curve - common isotopes.svg|thumb|upright=1.2|Binding energy per nucleon of common isotopes.]]
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{{further|List of nuclides}}
{{further|List of nuclides}}


It is expected that some continual improvement of experimental sensitivity will allow discovery of very mild radioactivity (instability) of some isotopes that are considered to be stable today. For example, in 2003 it was reported that [[bismuth-209]] (the only primordial isotope of bismuth) is very mildly radioactive, with the half-life time of (1.9 ± 0.2) × 10<sup>19</sup> yr,<ref>{{Cite web|url=http://nucleardata.nuclear.lu.se/nucleardata/toi/listnuc.asp?sql=&HlifeMin=1e30&tMinStr=1e30+s&HlifeMax=1e40&tMaxStr=1e+40+s|title=WWW Table of Radioactive Isotopes}} {{dead link|date=May 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref>{{cite journal |last = Marcillac |first = Pierre de |author2 = Noël Coron |author3 = Gérard Dambier |author4 = Jacques Leblanc |author5 = Jean-Pierre Moalic |name-list-style = amp |date=2003 |title = Experimental detection of α-particles from the radioactive decay of natural bismuth |journal = Nature |volume = 422 |pages = 876–878 |pmid=12712201 |doi = 10.1038/nature01541 |issue = 6934 |bibcode= 2003Natur.422..876D|s2cid = 4415582 }}</ref> confirming earlier theoretical predictions<ref>{{cite journal |author= de Carvalho H. G., de Araújo Penna M.|title = Alpha-activity of <sup>209</sup>Bi |journal = Lett. Nuovo Cimento |date=1972 |volume = 3 |issue = 18 |pages = 720–722 |doi = 10.1007/BF02824346 |url=https://link.springer.com/article/10.1007/BF02824346}}</ref> from [[nuclear physics]] that bismuth-209 would decay very slowly by [[alpha emission]].
It is expected that improvement of experimental sensitivity will allow discovery of very mild radioactivity of some isotopes now considered stable. For example, in 2003 it was reported that [[bismuth-209]] (the only primordial isotope of bismuth) is very mildly radioactive, with half-life (1.9 ± 0.2) × 10{{sup|19}} yr,<ref>{{Cite web|url=http://nucleardata.nuclear.lu.se/nucleardata/toi/listnuc.asp?sql=&HlifeMin=1e30&tMinStr=1e30+s&HlifeMax=1e40&tMaxStr=1e+40+s|title=WWW Table of Radioactive Isotopes}} {{dead link|date=May 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref>{{cite journal |last = Marcillac |first = Pierre de |author2 = Noël Coron |author3 = Gérard Dambier |author4 = Jacques Leblanc |author5 = Jean-Pierre Moalic |name-list-style = amp |date=2003 |title = Experimental detection of α-particles from the radioactive decay of natural bismuth |journal = Nature |volume = 422 |pages = 876–878 |pmid=12712201 |doi = 10.1038/nature01541 |issue = 6934 |bibcode= 2003Natur.422..876D|s2cid = 4415582 }}</ref> confirming earlier theoretical predictions<ref>{{cite journal |author= de Carvalho H. G., de Araújo Penna M.|title = Alpha-activity of {{sup|209}}Bi |journal = Lett. Nuovo Cimento |date=1972 |volume = 3 |issue = 18 |pages = 720–722 |doi = 10.1007/BF02824346 |url=https://link.springer.com/article/10.1007/BF02824346}}</ref> from [[nuclear physics]] that bismuth-209 would very slowly [[alpha decay]].


Isotopes that are theoretically believed to be unstable but have not been observed to decay are termed as '''observationally stable'''. Currently there are 105 "stable" isotopes which are theoretically unstable, 40 of which have been observed in detail with no sign of decay, the lightest in any case being <sup>36</sup>Ar. Many "stable" nuclides are "[[metastable]]" inasmuch as they would release energy if a radioactive decay were to occur,<ref>{{cite web|url=http://www.nndc.bnl.gov/masses/|title=NNDC – Atomic Masses|website=www.nndc.bnl.gov|access-date=2009-01-17|archive-date=2019-01-11|archive-url=https://web.archive.org/web/20190111232533/http://www.nndc.bnl.gov/masses/|url-status=dead}}</ref> and are, in fact, expected to undergo very rare kinds of [[radioactive decay]], including [[double beta decay|double-beta emission]].
Isotopes that are theoretically believed to be unstable but have not been observed to decay are termed '''observationally stable'''. Currently there are 105 "stable" isotopes which are theoretically unstable, 40 of which have been observed in detail with no sign of decay, the lightest in any case being {{sup|36}}Ar. Many "stable" nuclides are "[[metastable]]" in that they would release energy if they were to decay,<ref>{{cite web|url=http://www.nndc.bnl.gov/masses/|title=NNDC – Atomic Masses|website=www.nndc.bnl.gov|access-date=2009-01-17|archive-date=2019-01-11|archive-url=https://web.archive.org/web/20190111232533/http://www.nndc.bnl.gov/masses/|url-status=dead}}</ref> and are expected to undergo very rare kinds of [[radioactive decay]], including [[double beta decay]].


146 nuclides from 62 elements with [[atomic number]]s from 1 ([[hydrogen]]) through 66 ([[dysprosium]]) except 43 ([[technetium]]), 61 ([[promethium]]), 62 ([[samarium]]), and 63 ([[europium]]) are theoretically stable to any kind of nuclear decay—except for the theoretical possibility of [[proton decay]], which has never been observed despite extensive searches for it—and [[spontaneous fission]], which is theoretically possible for the nuclides with [[atomic mass number]]s ≥ 93.<ref name=nucleonica/>
146 nuclides from 62 elements with [[atomic number]]s from 1 ([[hydrogen]]) through 66 ([[dysprosium]]) except 43 ([[technetium]]), 61 ([[promethium]]), 62 ([[samarium]]), and 63 ([[europium]]) are theoretically stable to any kind of nuclear decay — except for the theoretical possibility of [[proton decay]], which has never been observed despite extensive searches for it; and [[spontaneous fission]] (SF), which is theoretically possible for the nuclides with [[atomic mass number]]s ≥ 93.<ref name=nucleonica/>


For processes other than spontaneous fission, other theoretical decay routes for heavier elements include:<ref name=nucleonica>[http://www.nucleonica.net/unc.aspx Nucleonica website]</ref>
Besides SF, other theoretical decay routes for heavier elements include:<ref name=nucleonica>[http://www.nucleonica.net/unc.aspx Nucleonica website]</ref>
* [[alpha decay]] – 70 heavy [[nuclide]]s (the lightest two are [[cerium]]-142 and [[neodymium]]-143)
* [[alpha decay]] – 70 heavy [[nuclide]]s (the lightest two are [[cerium]]-142 and [[neodymium]]-143)
* [[double beta decay]] – 55 nuclides
* [[double beta decay]] – 55 nuclides
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* [[isomeric transition]] – tantalum-180m
* [[isomeric transition]] – tantalum-180m


These include all nuclides of mass 165 and greater. [[Argon-36]] is presently the lightest known "stable" nuclide which is theoretically unstable.<ref name=nucleonica/>
These include all nuclides of mass 165 and greater. [[Argon-36]] is the lightest known "stable" nuclide which is theoretically unstable.<ref name=nucleonica/>


The positivity of energy release in these processes means that they are allowed kinematically (they do not violate the conservation of energy) and, thus, in principle, can occur.<ref name=nucleonica/> They are not observed due to strong but not absolute suppression, by spin-parity selection rules (for beta decays and isomeric transitions) or by the thickness of the potential barrier (for alpha and cluster decays and spontaneous fission).
The positivity of energy release in these processes means they are allowed kinematically (they do not violate conservation of energy) and, thus, in principle, can occur.<ref name=nucleonica/> They are not observed due to strong but not absolute suppression, by spin-parity selection rules (for beta decays and isomeric transitions) or by the thickness of the potential barrier (for alpha and cluster decays and spontaneous fission).


== Summary table for numbers of each class of nuclides ==
== Summary table for numbers of each class of nuclides ==


This is a summary table from [[List of nuclides]]. Note that numbers are not exact and may change slightly in the future, as nuclides are observed to be radioactive, or new half-lives are determined to some precision.
This is a summary table from [[List of nuclides]]. Numbers are not exact and may change slightly in the future, as nuclides are observed to be radioactive, or new half-lives are determined to some precision.


{| class="wikitable sortable" style="max-width:1120px;" |
{| class="wikitable sortable" style="max-width:1120px;" |
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| style="text-align:right;" | 146
| style="text-align:right;" | 146
| style="text-align:right;" | 146
| style="text-align:right;" | 146
|Contains the first 66 elements, except 43, 61, 62, and 63. If [[spontaneous fission]] is possible for the nuclides with [[mass number]]s ≥ 93, then all such nuclides are unstable (which is made irrelevant by the fact that all elements heavier than [[Lead]] are radioactive); also, if [[Proton decay|protons decay]], then there are no stable nuclides.
|All the first 66 elements, except 43, 61, 62, and 63. If [[spontaneous fission]] is possible for the nuclides with [[mass number]]s ≥ 93, then all such nuclides are unstable, so that only the first 40 elements would be stable. If [[Proton decay|protons decay]], then there are no stable nuclides.
|-
|-
| Energetically unstable to one or more known decay modes, but no decay yet seen. Considered stable until radioactivity confirmed.
| Energetically unstable to one or more known decay modes, but no decay yet seen. Considered stable until radioactivity confirmed.
| style="text-align:right;" | 105<ref name="bellidecay"/><ref name="Tretyak2002"/>
| style="text-align:right;" | 105<ref name="bellidecay"/><ref name="Tretyak2002"/>
| style="text-align:right;" | 251
| style="text-align:right;" | 251
| Total is the observationally stable nuclides. All elements lighter than [[Lead]] (Except [[Technetium]] and [[Promethium]]) are included.
| Total is the observationally stable nuclides. All elements up to [[lead]] (except [[technetium]] and [[promethium]]) are included.
|-
|-
| Radioactive [[primordial nuclide]]s.
| Radioactive [[primordial nuclide]]s.
| style="text-align:right;" | 35
| style="text-align:right;" | 35
| style="text-align:right;" | 286
| style="text-align:right;" | 286
| Includes Bi, Th, U
| Includes [[bismuth]], [[thorium]], and [[uranium]]
|-
|-
| Radioactive nonprimordial, but naturally occurring on Earth.
| Radioactive nonprimordial, but occur naturally on Earth.
| style="text-align:right;" | ~61 significant
| style="text-align:right;" | ~61 significant
| style="text-align:right;" | ~347 significant
| style="text-align:right;" | ~347 significant
Line 105: Line 106:


== List of stable nuclides ==
== List of stable nuclides ==
The primordial radionuclides have been included for comparison; they are italicised and offset from the list of stable nuclides proper.
The primordial radionuclides are included for comparison; they are italicized and offset from the list of stable nuclides proper.
{{div col|colwidth=19em}}
{{div col|colwidth=19em}}
{{ordered list|list-style-type=decimal
{{ordered list
| list-style-type = decimal|[[Hydrogen-1]]|Hydrogen-2 ([[deuterium]])|[[Helium-4]]
| [[Hydrogen-1]]
: ''no mass number 5''|[[Lithium-6]]|[[Lithium-7]]
| [[Hydrogen-2]]
: ''no mass number 8''|[[Beryllium-9]]|[[Boron-10]]|[[Boron-11]]|[[Carbon-12]]|[[Carbon-13]]|[[Nitrogen-14]]|[[Nitrogen-15]]|[[Oxygen-16]]|[[Oxygen-17]]|[[Oxygen-18]]|[[Fluorine-19]]|[[Neon-20]]|[[Neon-21]]|[[Neon-22]]|[[Sodium-23]]|[[Magnesium-24]]|[[Magnesium-25]]|[[Magnesium-26]]|[[Aluminium-27]]|[[Silicon-28]]|[[Silicon-29]]|[[Silicon-30]]|[[Phosphorus-31]]|[[Sulfur-32]]|[[Sulfur-33]]|[[Sulfur-34]]|[[Sulfur-36]]|[[Chlorine-35]]|[[Chlorine-37]]|[[Argon-36]] (2E)|[[Argon-38]]|[[Argon-40]]|[[Potassium-39]]
| [[Helium-3]]
: ''[[Potassium-40]]'' (B, E) – long-lived primordial radionuclide|[[Potassium-41]]|[[Calcium-40]] (2E)*|[[Calcium-42]]|[[Calcium-43]]|[[Calcium-44]]|[[Calcium-46]] (2B)*
| [[Helium-4]]
: ''[[Calcium-48]]'' (2B) – long-lived primordial radionuclide (B also predicted possible)|[[Scandium-45]]|[[Titanium-46]]|[[Titanium-47]]|[[Titanium-48]]|[[Titanium-49]]|[[Titanium-50]]
: ''no mass number 5''
: ''[[Vanadium-50]]'' (B, E) – long-lived primordial radionuclide|[[Vanadium-51]]|[[Chromium-50]] (2E)*|[[Chromium-52]]|[[Chromium-53]]|[[Chromium-54]]|[[Manganese-55]]|[[Iron-54]] (2E)*|[[Iron-56]]|[[Iron-57]]|[[Iron-58]]|[[Cobalt-59]]|[[Nickel-58]] (2E)*|[[Nickel-60]]|[[Nickel-61]]|[[Nickel-62]]|[[Nickel-64]]|[[Copper-63]]|[[Copper-65]]|[[Zinc-64]] (2E)*|[[Zinc-66]]|[[Zinc-67]]|[[Zinc-68]]|[[Zinc-70]] (2B)*|[[Gallium-69]]|[[Gallium-71]]|[[Germanium-70]]|[[Germanium-72]]|[[Germanium-73]]|[[Germanium-74]]
| [[Lithium-6]]
: ''[[Germanium-76]]'' (2B) – long-lived primordial radionuclide|[[Arsenic-75]]|[[Selenium-74]] (2E)|[[Selenium-76]]|[[Selenium-77]]|[[Selenium-78]]|[[Selenium-80]] (2B)
| [[Lithium-7]]
: ''[[Selenium-82]]'' (2B) – long-lived primordial radionuclide|[[Bromine-79]]|[[Bromine-81]]
: ''no mass number 8''
: ''[[Krypton-78]]'' (2E) – long-lived primordial radionuclide|[[Krypton-80]]|[[Krypton-82]]|[[Krypton-83]]|[[Krypton-84]]|[[Krypton-86]] (2B)|[[Rubidium-85]]
| [[Beryllium-9]]
: ''[[Rubidium-87]]'' (B) – long-lived primordial radionuclide|[[Strontium-84]] (2E)*|[[Strontium-86]]|[[Strontium-87]]|[[Strontium-88]]|[[Yttrium-89]]|[[Zirconium-90]]|[[Zirconium-91]]|[[Zirconium-92]]|[[Zirconium-94]] (2B)*
| [[Boron-10]]
: ''[[Zirconium-96]]'' (2B) – long-lived primordial radionuclide (B also predicted possible)|[[Niobium-93]]|[[Molybdenum-92]] (2E)*|[[Molybdenum-94]]|[[Molybdenum-95]]|[[Molybdenum-96]]|[[Molybdenum-97]]|[[Molybdenum-98]] (2B)*
| [[Boron-11]]
| [[Carbon-12]]
| [[Carbon-13]]
| [[Nitrogen-14]]
| [[Nitrogen-15]]
| [[Oxygen-16]]
| [[Oxygen-17]]
| [[Oxygen-18]]
| [[Fluorine-19]]
| [[Neon-20]]
| [[Neon-21]]
| [[Neon-22]]
| [[Sodium-23]]
| [[Magnesium-24]]
| [[Magnesium-25]]
| [[Magnesium-26]]
| [[Aluminium-27]]
| [[Silicon-28]]
| [[Silicon-29]]
| [[Silicon-30]]
| [[Phosphorus-31]]
| [[Sulfur-32]]
| [[Sulfur-33]]
| [[Sulfur-34]]
| [[Sulfur-36]]
| [[Chlorine-35]]
| [[Chlorine-37]]
| [[Argon-36]] (2E)
| [[Argon-38]]
| [[Argon-40]]
| [[Potassium-39]]
: ''[[Potassium-40]]'' (B, E) – long-lived primordial radionuclide
| [[Potassium-41]]
| [[Calcium-40]] (2E)*
| [[Calcium-42]]
| [[Calcium-43]]
| [[Calcium-44]]
| [[Calcium-46]] (2B)*
: ''[[Calcium-48]]'' (2B) – long-lived primordial radionuclide (B also predicted possible)
| [[Scandium-45]]
| [[Titanium-46]]
| [[Titanium-47]]
| [[Titanium-48]]
| [[Titanium-49]]
| [[Titanium-50]]
: ''[[Vanadium-50]]'' (B, E) – long-lived primordial radionuclide
| [[Vanadium-51]]
| [[Chromium-50]] (2E)*
| [[Chromium-52]]
| [[Chromium-53]]
| [[Chromium-54]]
| [[Manganese-55]]
| [[Iron-54]] (2E)*
| [[Iron-56]]
| [[Iron-57]]
| [[Iron-58]]
| [[Cobalt-59]]
| [[Nickel-58]] (2E)*
| [[Nickel-60]]
| [[Nickel-61]]
| [[Nickel-62]]
| [[Nickel-64]]
| [[Copper-63]]
| [[Copper-65]]
| [[Zinc-64]] (2E)*
| [[Zinc-66]]
| [[Zinc-67]]
| [[Zinc-68]]
| [[Zinc-70]] (2B)*
| [[Gallium-69]]
| [[Gallium-71]]
| [[Germanium-70]]
| [[Germanium-72]]
| [[Germanium-73]]
| [[Germanium-74]]
: ''[[Germanium-76]]'' (2B) – long-lived primordial radionuclide
| [[Arsenic-75]]
| [[Selenium-74]] (2E)
| [[Selenium-76]]
| [[Selenium-77]]
| [[Selenium-78]]
| [[Selenium-80]] (2B)
: ''[[Selenium-82]]'' (2B) – long-lived primordial radionuclide
| [[Bromine-79]]
| [[Bromine-81]]
: ''[[Krypton-78]]'' (2E) – long-lived primordial radionuclide
| [[Krypton-80]]
| [[Krypton-82]]
| [[Krypton-83]]
| [[Krypton-84]]
| [[Krypton-86]] (2B)
| [[Rubidium-85]]
: ''[[Rubidium-87]]'' (B) – long-lived primordial radionuclide
| [[Strontium-84]] (2E)*
| [[Strontium-86]]
| [[Strontium-87]]
| [[Strontium-88]]
| [[Yttrium-89]]
| [[Zirconium-90]]
| [[Zirconium-91]]
| [[Zirconium-92]]
| [[Zirconium-94]] (2B)*
: ''[[Zirconium-96]]'' (2B) – long-lived primordial radionuclide (B also predicted possible)
| [[Niobium-93]]
| [[Molybdenum-92]] (2E)*
| [[Molybdenum-94]]
| [[Molybdenum-95]]
| [[Molybdenum-96]]
| [[Molybdenum-97]]
| [[Molybdenum-98]] (2B)*
: ''[[Molybdenum-100]]'' (2B) – long-lived primordial radionuclide
: ''[[Molybdenum-100]]'' (2B) – long-lived primordial radionuclide
: [[Isotopes of technetium|Technetium]] – ''no stable isotopes''|[[Ruthenium-96]] (2E)*|[[Ruthenium-98]]|[[Ruthenium-99]]|[[Ruthenium-100]]|[[Ruthenium-101]]|[[Ruthenium-102]]|[[Ruthenium-104]] (2B)|[[Rhodium-103]]|[[Palladium-102]] (2E)|[[Palladium-104]]|[[Palladium-105]]|[[Palladium-106]]|[[Palladium-108]]|[[Palladium-110]] (2B)*|[[Silver-107]]|[[Silver-109]]|[[Cadmium-106]] (2E)*|[[Cadmium-108]] (2E)*|[[Cadmium-110]]|[[Cadmium-111]]|[[Cadmium-112]]
: [[Isotopes of technetium|Technetium]] – ''no stable isotopes''
: ''[[Cadmium-113]]'' (B) – long-lived primordial radionuclide|[[Cadmium-114]] (2B)*
| [[Ruthenium-96]] (2E)*
: ''[[Cadmium-116]]'' (2B) – long-lived primordial radionuclide|[[Indium-113]]
| [[Ruthenium-98]]
: ''[[Indium-115]]'' (B) – long-lived primordial radionuclide|[[Tin-112]] (2E)*|[[Tin-114]]|[[Tin-115]]|[[Tin-116]]|[[Tin-117]]|[[Tin-118]]|[[Tin-119]]|[[Tin-120]]|[[Tin-122]] (2B)*|[[Tin-124]] (2B)*|[[Antimony-121]]|[[Antimony-123]]|[[Tellurium-120]] (2E)*|[[Tellurium-122]]|[[Tellurium-123]] (E)*|[[Tellurium-124]]|[[Tellurium-125]]|[[Tellurium-126]]
| [[Ruthenium-99]]
| [[Ruthenium-100]]
| [[Ruthenium-101]]
| [[Ruthenium-102]]
| [[Ruthenium-104]] (2B)
| [[Rhodium-103]]
| [[Palladium-102]] (2E)
| [[Palladium-104]]
| [[Palladium-105]]
| [[Palladium-106]]
| [[Palladium-108]]
| [[Palladium-110]] (2B)*
| [[Silver-107]]
| [[Silver-109]]
| [[Cadmium-106]] (2E)*
| [[Cadmium-108]] (2E)*
| [[Cadmium-110]]
| [[Cadmium-111]]
| [[Cadmium-112]]
: ''[[Cadmium-113]]'' (B) – long-lived primordial radionuclide
| [[Cadmium-114]] (2B)*
: ''[[Cadmium-116]]'' (2B) – long-lived primordial radionuclide
| [[Indium-113]]
: ''[[Indium-115]]'' (B) – long-lived primordial radionuclide
| [[Tin-112]] (2E)*
| [[Tin-114]]
| [[Tin-115]]
| [[Tin-116]]
| [[Tin-117]]
| [[Tin-118]]
| [[Tin-119]]
| [[Tin-120]]
| [[Tin-122]] (2B)*
| [[Tin-124]] (2B)*
| [[Antimony-121]]
| [[Antimony-123]]
| [[Tellurium-120]] (2E)*
| [[Tellurium-122]]
| [[Tellurium-123]] (E)*
| [[Tellurium-124]]
| [[Tellurium-125]]
| [[Tellurium-126]]
: ''[[Tellurium-128]]'' (2B) – long-lived primordial radionuclide
: ''[[Tellurium-128]]'' (2B) – long-lived primordial radionuclide
: ''[[Tellurium-130]]'' (2B) – long-lived primordial radionuclide
: ''[[Tellurium-130]]'' (2B) – long-lived primordial radionuclide|[[Iodine-127]]
: ''[[Xenon-124]]'' (2E) – long-lived primordial radionuclide|[[Xenon-126]] (2E)|[[Xenon-128]]|[[Xenon-129]]|[[Xenon-130]]|[[Xenon-131]]|[[Xenon-132]]|[[Xenon-134]] (2B)*
| [[Iodine-127]]
: ''[[Xenon-124]]'' (2E) – long-lived primordial radionuclide
: ''[[Xenon-136]]'' (2B) – long-lived primordial radionuclide|[[Caesium-133]]
: ''[[Barium-130]]'' (2E) – long-lived primordial radionuclide|[[Barium-132]] (2E)*|[[Barium-134]]|[[Barium-135]]|[[Barium-136]]|[[Barium-137]]|[[Barium-138]]
| [[Xenon-126]] (2E)
: ''[[Lanthanum-138]]'' (B, E) – long-lived primordial radionuclide|[[Lanthanum-139]]|[[Cerium-136]] (2E)*|[[Cerium-138]] (2E)*|[[Cerium-140]]|[[Cerium-142]] (α, 2B)*|[[Praseodymium-141]]|[[Neodymium-142]]|[[Neodymium-143]] (α)
| [[Xenon-128]]
: ''[[Neodymium-144]]'' (α) – long-lived primordial radionuclide|[[Neodymium-145]] (α)*|[[Neodymium-146]] (α, 2B)*
| [[Xenon-129]]
: ''no mass number 147<sup>§</sup>''|[[Neodymium-148]] (α, 2B)*
| [[Xenon-130]]
| [[Xenon-131]]
| [[Xenon-132]]
| [[Xenon-134]] (2B)*
: ''[[Xenon-136]]'' (2B) – long-lived primordial radionuclide
| [[Caesium-133]]
: ''[[Barium-130]]'' (2E) – long-lived primordial radionuclide
| [[Barium-132]] (2E)*
| [[Barium-134]]
| [[Barium-135]]
| [[Barium-136]]
| [[Barium-137]]
| [[Barium-138]]
: ''[[Lanthanum-138]]'' (B, E) – long-lived primordial radionuclide
| [[Lanthanum-139]]
| [[Cerium-136]] (2E)*
| [[Cerium-138]] (2E)*
| [[Cerium-140]]
| [[Cerium-142]] (A, 2B)*
| [[Praseodymium-141]]
| [[Neodymium-142]]
| [[Neodymium-143]] (A)
: ''[[Neodymium-144]]'' (A) – long-lived primordial radionuclide
| [[Neodymium-145]] (A)*
| [[Neodymium-146]] (A, 2B)*
: ''no mass number 147<sup>§</sup>''
| [[Neodymium-148]] (A, 2B)*
: ''[[Neodymium-150]]'' (2B) – long-lived primordial radionuclide
: ''[[Neodymium-150]]'' (2B) – long-lived primordial radionuclide
: [[Isotopes of promethium|Promethium]] - ''no stable isotopes''
: [[Isotopes of promethium|Promethium]] - ''no stable isotopes''|[[Samarium-144]] (2E)
| [[Samarium-144]] (2E)
: ''[[Samarium-146]]'' (α) – probable long-lived primordial radionuclide
: ''[[Samarium-146]]'' (A) – probable long-lived primordial radionuclide
: ''[[Samarium-147]]'' (α) – long-lived primordial radionuclide
: ''[[Samarium-147]]'' (A) – long-lived primordial radionuclide
: ''[[Samarium-148]]'' (α) – long-lived primordial radionuclide|[[Samarium-149]] (α)*|[[Samarium-150]] (α)
: ''[[Samarium-148]]'' (A) – long-lived primordial radionuclide
: ''no mass number 151<sup>§</sup>''|[[Samarium-152]] (α)|[[Samarium-154]] (2B)*
: ''[[Europium-151]]'' (α) – long-lived primordial radionuclide|[[Europium-153]] (α)*
| [[Samarium-149]] (A)*
: ''[[Gadolinium-152]]'' (α) – long-lived primordial radionuclide (2E also predicted possible)|[[Gadolinium-154]] (α)|[[Gadolinium-155]] (α)|[[Gadolinium-156]]|[[Gadolinium-157]]|[[Gadolinium-158]]|[[Gadolinium-160]] (2B)*|[[Terbium-159]]|[[Dysprosium-156]] (α, 2E)*|[[Dysprosium-158]] (α)|[[Dysprosium-160]] (α)|[[Dysprosium-161]] (α)|[[Dysprosium-162]] (α)|[[Dysprosium-163]]|[[Dysprosium-164]]|[[Holmium-165]] (α)|[[Erbium-162]] (α, 2E)*|[[Erbium-164]] (α, 2E)|[[Erbium-166]] (α)|[[Erbium-167]] (α)|[[Erbium-168]] (α)|[[Erbium-170]] (α, 2B)*|[[Thulium-169]] (α)|[[Ytterbium-168]] (α, 2E)*|[[Ytterbium-170]] (α)|[[Ytterbium-171]] (α)|[[Ytterbium-172]] (α)|[[Ytterbium-173]] (α)|[[Ytterbium-174]] (α)|[[Ytterbium-176]] (α, 2B)*|[[Lutetium-175]] (α)
| [[Samarium-150]] (A)
: ''[[Lutetium-176]]'' (B) – long-lived primordial radionuclide (α, E also predicted possible)
: ''no mass number 151<sup>§</sup>''
: ''[[Hafnium-174]]'' (α) – long-lived primordial radionuclide (2E also predicted possible)|[[Hafnium-176]] (α)|[[Hafnium-177]] (α)|[[Hafnium-178]] (α)|[[Hafnium-179]] (α)|[[Hafnium-180]] (α)|[[Tantalum-180m]] (α, B, E, IT)* '''^'''|[[Tantalum-181]] (α)
| [[Samarium-152]] (A)
: ''[[Tungsten-180]]'' (α) – long-lived primordial radionuclide (2E also predicted possible)|[[Tungsten-182]] (α)*|[[Tungsten-183]] (α)*|[[Tungsten-184]] (α)*|[[Tungsten-186]] (α, 2B)*|[[Rhenium-185]] (α)
| [[Samarium-154]] (2B)*
: ''[[Europium-151]]'' (A) – long-lived primordial radionuclide
| [[Europium-153]] (A)*
: ''[[Gadolinium-152]]'' (A) – long-lived primordial radionuclide (2E also predicted possible)
| [[Gadolinium-154]] (A)
| [[Gadolinium-155]] (A)
| [[Gadolinium-156]]
| [[Gadolinium-157]]
| [[Gadolinium-158]]
| [[Gadolinium-160]] (2B)*
| [[Terbium-159]]
| [[Dysprosium-156]] (A, 2E)*
| [[Dysprosium-158]] (A)
| [[Dysprosium-160]] (A)
| [[Dysprosium-161]] (A)
| [[Dysprosium-162]] (A)
| [[Dysprosium-163]]
| [[Dysprosium-164]]
| [[Holmium-165]] (A)
| [[Erbium-162]] (A, 2E)*
| [[Erbium-164]] (A, 2E)
| [[Erbium-166]] (A)
| [[Erbium-167]] (A)
| [[Erbium-168]] (A)
| [[Erbium-170]] (A, 2B)*
| [[Thulium-169]] (A)
| [[Ytterbium-168]] (A, 2E)*
| [[Ytterbium-170]] (A)
| [[Ytterbium-171]] (A)
| [[Ytterbium-172]] (A)
| [[Ytterbium-173]] (A)
| [[Ytterbium-174]] (A)
| [[Ytterbium-176]] (A, 2B)*
| [[Lutetium-175]] (A)
: ''[[Lutetium-176]]'' (B) – long-lived primordial radionuclide (A, E also predicted possible)
: ''[[Hafnium-174]]'' (A) – long-lived primordial radionuclide (2E also predicted possible)
| [[Hafnium-176]] (A)
| [[Hafnium-177]] (A)
| [[Hafnium-178]] (A)
| [[Hafnium-179]] (A)
| [[Hafnium-180]] (A)
| [[Tantalum-180m]] (A, B, E, IT)* '''^'''
| [[Tantalum-181]] (A)
: ''[[Tungsten-180]]'' (A) – long-lived primordial radionuclide (2E also predicted possible)
| [[Tungsten-182]] (A)*
| [[Tungsten-183]] (A)*
| [[Tungsten-184]] (A)*
| [[Tungsten-186]] (A, 2B)*
| [[Rhenium-185]] (A)
: ''[[Rhenium-187]]'' (B) – long-lived primordial radionuclide (A also predicted possible)
: ''[[Rhenium-187]]'' (B) – long-lived primordial radionuclide (A also predicted possible)
: ''[[Osmium-184]]'' (A) – long-lived primordial radionuclide (2E also predicted possible)
: ''[[Osmium-184]]'' (α) – long-lived primordial radionuclide (2E also predicted possible)
: ''[[Osmium-186]]'' (A) – long-lived primordial radionuclide
: ''[[Osmium-186]]'' (α) – long-lived primordial radionuclide|[[Osmium-187]] (α)|[[Osmium-188]] (α)|[[Osmium-189]] (α)|[[Osmium-190]] (α)|[[Osmium-192]] (α, 2B)*|[[Iridium-191]] (α)|[[Iridium-193]] (α)
: ''[[Platinum-190]]'' (α) – long-lived primordial radionuclide (2E also predicted possible)|[[Platinum-192]] (α)*|[[Platinum-194]] (α)|[[Platinum-195]] (α)*|[[Platinum-196]] (α)|[[Platinum-198]] (α, 2B)*|[[Gold-197]] (α)|[[Mercury-196]] (α, 2E)*|[[Mercury-198]] (α)|[[Mercury-199]] (α)|[[Mercury-200]] (α)|[[Mercury-201]] (α)|[[Mercury-202]] (α)|[[Mercury-204]] (2B)|[[Thallium-203]] (α)|[[Thallium-205]] (α)|[[Lead-204]] (α)*|[[Lead-206]] (α)*|[[Lead-207]] (α)*|[[Lead-208]] (α)*
| [[Osmium-187]] (A)
| [[Osmium-188]] (A)
| [[Osmium-189]] (A)
| [[Osmium-190]] (A)
| [[Osmium-192]] (A, 2B)*
| [[Iridium-191]] (A)
| [[Iridium-193]] (A)
: ''[[Platinum-190]]'' (A) – long-lived primordial radionuclide (2E also predicted possible)
| [[Platinum-192]] (A)*
| [[Platinum-194]] (A)
| [[Platinum-195]] (A)*
| [[Platinum-196]] (A)
| [[Platinum-198]] (A, 2B)*
| [[Gold-197]] (A)
| [[Mercury-196]] (A, 2E)*
| [[Mercury-198]] (A)
| [[Mercury-199]] (A)
| [[Mercury-200]] (A)
| [[Mercury-201]] (A)
| [[Mercury-202]] (A)
| [[Mercury-204]] (2B)
| [[Thallium-203]] (A)
| [[Thallium-205]] (A)
| [[Lead-204]] (A)*
| [[Lead-206]] (A)*
| [[Lead-207]] (A)*
| [[Lead-208]] (A)*
: [[Isotopes of bismuth|Bismuth]] '''^^''' and above –
: [[Isotopes of bismuth|Bismuth]] '''^^''' and above –
:: ''no stable isotopes''
:: ''no stable isotopes''
: ''no mass number 209 and above''
: ''no mass number 209 and above''
: ''[[Bismuth-209]]'' (A) – long-lived primordial radionuclide
: ''[[Bismuth-209]]'' (α) – long-lived primordial radionuclide
: ''[[Thorium-232]]'' (A, SF) – long-lived primordial radionuclide (2B also predicted possible)
: ''[[Thorium-232]]'' (α, SF) – long-lived primordial radionuclide (2B also predicted possible)
: ''[[Uranium-235]]'' (A, SF) – long-lived primordial radionuclide
: ''[[Uranium-235]]'' (α, SF) – long-lived primordial radionuclide
: ''[[Uranium-238]]'' (A, 2B, SF) – long-lived primordial radionuclide
: ''[[Uranium-238]]'' (α, 2B, SF) – long-lived primordial radionuclide
: ''[[Plutonium-244]]'' (A, SF) – probable long-lived primordial radionuclide (2B also predicted possible)
: ''[[Plutonium-244]]'' (α, SF) – probable long-lived primordial radionuclide (2B also predicted possible)
}}
}}
{{div col end}}
{{div col end}}
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|bibcode=2002ADNDT..80...83T }}</ref>
|bibcode=2002ADNDT..80...83T }}</ref>


'''A''' for alpha decay, '''B''' for beta decay, '''2B''' for double beta decay, '''E''' for electron capture, '''2E''' for double electron capture, '''IT''' for isomeric transition, '''SF''' for spontaneous fission, '''*''' for the nuclides whose half-lives have lower bound. Double beta decay has only been listed when beta decay is not also possible.
'''α''' for alpha decay, '''B''' for beta decay, '''2B''' for double beta decay, '''E''' for electron capture, '''2E''' for double electron capture, '''IT''' for isomeric transition, '''SF''' for spontaneous fission, '''*''' for the nuclides whose half-lives have lower bound. Double beta decay has only been listed when beta decay is not also possible.


'''^''' Tantalum-180m is a "metastable isotope" meaning that it is an excited [[nuclear isomer]] of tantalum-180. See [[isotopes of tantalum]]. However, the half-life of this nuclear isomer is so long that it has never been observed to decay, and it thus occurs as an "observationally nonradioactive" [[primordial nuclide]], as a minor isotope of tantalum. This is the only case of a nuclear isomer which has a half-life so long that it has never been observed to decay. It is thus included in this list.
'''^''' Tantalum-180m is a "metastable isotope", meaning it is an excited [[nuclear isomer]] of tantalum-180. See [[isotopes of tantalum]]. However, the half-life of this nuclear isomer is so long that it has never been observed to decay, and it thus is an "observationally stable" [[primordial nuclide]], a rare isotope of tantalum. This is the only nuclear isomer with a half-life so long that it has never been observed to decay. It is thus included in this list.


'''^^''' [[Bismuth-209]] had long been believed to be stable, due to its unusually long half-life of 2.01&nbsp;·&nbsp;10<sup>19</sup> years, which is more than a billion times the age of the universe.
'''^^''' [[Bismuth-209]] was long believed to be stable, due to its half-life of 2.01×10{{sup|19}} years, which is more than a billion times the age of the universe.


'''§''' [[Europium-151]] and [[samarium-147]] are [[primordial nuclide]]s with very long half-lives of 5.004&nbsp;·&nbsp;10<sup>18</sup> years and 1.061&nbsp;·&nbsp;10<sup>11</sup> years, respectively.
'''§''' [[Europium-151]] and [[samarium-147]] are [[primordial nuclide]]s with very long half-lives of 4.62×10{{sup|18}} years and 1.066×10{{sup|11}} years, respectively.


==See also==
==See also==

Latest revision as of 18:41, 22 November 2024

Graph of nuclides (isotopes) by type of decay. Orange and blue nuclides are unstable, with the black squares between these regions representing stable nuclides. The continuous line passing below most of the nuclides comprises the positions on the graph of the (mostly hypothetical) nuclides for which proton number would be the same as neutron number. The graph reflects the fact that elements with more than 20 protons either have more neutrons than protons or are unstable.

Stable nuclides are isotopes of a chemical element whose nucleons are in a configuration that does not permit them the surplus energy required to produce a radioactive emission. The nuclei of such isotopes are not radioactive and unlike radionuclides do not spontaneously undergo radioactive decay.[1] When these nuclides are referred to in relation to specific elements they are usually called that element's stable isotopes.

The 80 elements with one or more stable isotopes comprise a total of 251 nuclides that have not been shown to decay using current equipment. Of these 80 elements, 26 have only one stable isotope and are called monoisotopic. The other 56 have more than one stable isotope. Tin has ten stable isotopes, the largest number of any element.

Definition of stability, and naturally occurring nuclides

[edit]

Most naturally occurring nuclides are stable (about 251; see list at the end of this article), and about 35 more (total of 286) are known to be radioactive with long enough half-lives (also known) to occur primordially. If the half-life of a nuclide is comparable to, or greater than, the Earth's age (4.5 billion years), a significant amount will have survived since the formation of the Solar System, and then is said to be primordial. It will then contribute in that way to the natural isotopic composition of a chemical element. Primordial radioisotopes are easily detected with half-lives as short as 700 million years (e.g., 235U). This is the present limit of detection,[citation needed] as shorter-lived nuclides have not yet been detected undisputedly in nature except when recently produced, such as decay products or cosmic ray spallation.

Many naturally occurring radioisotopes (another 53 or so, for a total of about 339) exhibit still shorter half-lives than 700 million years, but they are made freshly, as daughter products of decay processes of primordial nuclides (for example, radium from uranium), or from ongoing energetic reactions, such as cosmogenic nuclides produced by present bombardment of Earth by cosmic rays (for example, 14C made from nitrogen).

Some isotopes that are classed as stable (i.e. no radioactivity has been observed for them) are predicted to have extremely long half-lives (sometimes 1018 years or more).[2] If the predicted half-life falls into an experimentally accessible range, such isotopes have a chance to move from the list of stable nuclides to the radioactive category, once their activity is observed. For example, 209Bi and 180W were formerly classed as stable, but were found to be alpha-active in 2003. However, such nuclides do not change their status as primordial when they are found to be radioactive.

Most stable isotopes on Earth are believed to have been formed in processes of nucleosynthesis, either in the Big Bang, or in generations of stars that preceded the formation of the Solar System. However, some stable isotopes also show abundance variations in the earth as a result of decay from long-lived radioactive nuclides. These decay-products are termed radiogenic isotopes, in order to distinguish them from the much larger group of 'non-radiogenic' isotopes.

Isotopes per element

[edit]
See also: List of elements by stability of isotopes, List of nuclides, and Beta-decay stable isobars

Of the known chemical elements, 80 elements have at least one stable nuclide. These comprise the first 82 elements from hydrogen to lead, with the two exceptions, technetium (element 43) and promethium (element 61), that do not have any stable nuclides. As of 2024, there are total of 251 known "stable" nuclides. In this definition, "stable" means a nuclide that has never been observed to decay against the natural background. Thus, these elements have half-lives too long to be measured by any means, direct or indirect.

Stable isotopes:

  • 1 element (tin) has 10 stable isotopes
  • 5 elements have 7 stable isotopes apiece
  • 7 elements have 6 stable isotopes apiece
  • 11 elements have 5 stable isotopes apiece
  • 9 elements have 4 stable isotopes apiece
  • 5 elements have 3 stable isotopes apiece
  • 16 elements have 2 stable isotopes apiece
  • 26 elements have 1 single stable isotope.

These last 26 are thus called monoisotopic elements.[3] The mean number of stable isotopes for elements which have at least one stable isotope is 251/80 = 3.1375.

Physical magic numbers and odd and even proton and neutron count

[edit]
See also: Even and odd atomic nuclei

Stability of isotopes is affected by the ratio of protons to neutrons, and also by presence of certain magic numbers of neutrons or protons which represent closed and filled quantum shells. These quantum shells correspond to a set of energy levels within the shell model of the nucleus; filled shells, such as the filled shell of 50 protons for tin, confers unusual stability on the nuclide. As in the case of tin, a magic number for Z, the atomic number, tends to increase the number of stable isotopes for the element.

Just as in the case of electrons, which have the lowest energy state when they occur in pairs in a given orbital, nucleons (both protons and neutrons) exhibit a lower energy state when their number is even, rather than odd. This stability tends to prevent beta decay (in two steps) of many even–even nuclides into another even–even nuclide of the same mass number but lower energy (and of course with two more protons and two fewer neutrons), because decay proceeding one step at a time would have to pass through an odd–odd nuclide of higher energy. Such nuclei thus instead undergo double beta decay (or are theorized to do so) with half-lives several orders of magnitude larger than the age of the universe. This makes for a larger number of stable even–even nuclides, which account for 150 of the 251 total. Stable even–even nuclides number as many as three isobars for some mass numbers, and up to seven isotopes for some atomic numbers.

Conversely, of the 251 known stable nuclides, only five have both an odd number of protons and odd number of neutrons: hydrogen-2 (deuterium), lithium-6, boron-10, nitrogen-14, and tantalum-180m. Also, only four naturally occurring, radioactive odd–odd nuclides have a half-life >109 years: potassium-40, vanadium-50, lanthanum-138, and lutetium-176. Odd–odd primordial nuclides are rare because most odd–odd nuclei beta-decay, because the decay products are even–even, and are therefore more strongly bound, due to nuclear pairing effects.[4]

Yet another effect of the instability of an odd number of either type of nucleon is that odd-numbered elements tend to have fewer stable isotopes. Of the 26 monoisotopic elements (those with only one stable isotope), all but one have an odd atomic number, and all but one has an even number of neutrons: the single exception to both rules is beryllium.

The end of the stable elements occurs after lead, largely because nuclei with 128 neutrons—two neutrons above the magic number 126—are extraordinarily unstable and almost immediately alpha-decay.[5] This contributes to the very short half-lives of astatine, radon, and francium. A similar phenomenon occurs to a much lesser extent with 84 neutrons—two neutrons above the magic number 82—where various isotopes of lanthanide elements alpha-decay.

Nuclear isomers, including a "stable" one

[edit]

The 251 known stable nuclides include tantalum-180m, since even though its decay is automatically implied by its being "metastable", this has not been observed. All "stable" isotopes (stable by observation, not theory) are the ground states of nuclei, except for tantalum-180m, which is a nuclear isomer or excited state. The ground state, tantalum-180, is radioactive with half-life 8 hours; in contrast, the decay of the nuclear isomer is extremely strongly forbidden by spin-parity selection rules. It has been reported by direct observation that the half-life of 180mTa to gamma decay must be >1015 years. Other possible modes of 180mTa decay (beta decay, electron capture, and alpha decay) have also never been observed.

Binding energy per nucleon of common isotopes.

Still-unobserved decay

[edit]
Further information: List of nuclides

It is expected that improvement of experimental sensitivity will allow discovery of very mild radioactivity of some isotopes now considered stable. For example, in 2003 it was reported that bismuth-209 (the only primordial isotope of bismuth) is very mildly radioactive, with half-life (1.9 ± 0.2) × 1019 yr,[6][7] confirming earlier theoretical predictions[8] from nuclear physics that bismuth-209 would very slowly alpha decay.

Isotopes that are theoretically believed to be unstable but have not been observed to decay are termed observationally stable. Currently there are 105 "stable" isotopes which are theoretically unstable, 40 of which have been observed in detail with no sign of decay, the lightest in any case being 36Ar. Many "stable" nuclides are "metastable" in that they would release energy if they were to decay,[9] and are expected to undergo very rare kinds of radioactive decay, including double beta decay.

146 nuclides from 62 elements with atomic numbers from 1 (hydrogen) through 66 (dysprosium) except 43 (technetium), 61 (promethium), 62 (samarium), and 63 (europium) are theoretically stable to any kind of nuclear decay — except for the theoretical possibility of proton decay, which has never been observed despite extensive searches for it; and spontaneous fission (SF), which is theoretically possible for the nuclides with atomic mass numbers ≥ 93.[10]

Besides SF, other theoretical decay routes for heavier elements include:[10]

These include all nuclides of mass 165 and greater. Argon-36 is the lightest known "stable" nuclide which is theoretically unstable.[10]

The positivity of energy release in these processes means they are allowed kinematically (they do not violate conservation of energy) and, thus, in principle, can occur.[10] They are not observed due to strong but not absolute suppression, by spin-parity selection rules (for beta decays and isomeric transitions) or by the thickness of the potential barrier (for alpha and cluster decays and spontaneous fission).

Summary table for numbers of each class of nuclides

[edit]

This is a summary table from List of nuclides. Numbers are not exact and may change slightly in the future, as nuclides are observed to be radioactive, or new half-lives are determined to some precision.

Type of nuclide by stability class Number of nuclides in class Running total of nuclides in all classes to this point Notes
Theoretically stable according to known decay modes, including alpha decay, beta decay, isomeric transition, and double beta decay 146 146 All the first 66 elements, except 43, 61, 62, and 63. If spontaneous fission is possible for the nuclides with mass numbers ≥ 93, then all such nuclides are unstable, so that only the first 40 elements would be stable. If protons decay, then there are no stable nuclides.
Energetically unstable to one or more known decay modes, but no decay yet seen. Considered stable until radioactivity confirmed. 105[2][11] 251 Total is the observationally stable nuclides. All elements up to lead (except technetium and promethium) are included.
Radioactive primordial nuclides. 35 286 Includes bismuth, thorium, and uranium
Radioactive nonprimordial, but occur naturally on Earth. ~61 significant ~347 significant Cosmogenic nuclides from cosmic rays; daughters of radioactive primordials such as francium, etc.

List of stable nuclides

[edit]

The primordial radionuclides are included for comparison; they are italicized and offset from the list of stable nuclides proper.

  1. Hydrogen-1
  2. Hydrogen-2 (deuterium)
  3. Helium-4
    no mass number 5
  4. Lithium-6
  5. Lithium-7
    no mass number 8
  6. Beryllium-9
  7. Boron-10
  8. Boron-11
  9. Carbon-12
  10. Carbon-13
  11. Nitrogen-14
  12. Nitrogen-15
  13. Oxygen-16
  14. Oxygen-17
  15. Oxygen-18
  16. Fluorine-19
  17. Neon-20
  18. Neon-21
  19. Neon-22
  20. Sodium-23
  21. Magnesium-24
  22. Magnesium-25
  23. Magnesium-26
  24. Aluminium-27
  25. Silicon-28
  26. Silicon-29
  27. Silicon-30
  28. Phosphorus-31
  29. Sulfur-32
  30. Sulfur-33
  31. Sulfur-34
  32. Sulfur-36
  33. Chlorine-35
  34. Chlorine-37
  35. Argon-36 (2E)
  36. Argon-38
  37. Argon-40
  38. Potassium-39
    Potassium-40 (B, E) – long-lived primordial radionuclide
  39. Potassium-41
  40. Calcium-40 (2E)*
  41. Calcium-42
  42. Calcium-43
  43. Calcium-44
  44. Calcium-46 (2B)*
    Calcium-48 (2B) – long-lived primordial radionuclide (B also predicted possible)
  45. Scandium-45
  46. Titanium-46
  47. Titanium-47
  48. Titanium-48
  49. Titanium-49
  50. Titanium-50
    Vanadium-50 (B, E) – long-lived primordial radionuclide
  51. Vanadium-51
  52. Chromium-50 (2E)*
  53. Chromium-52
  54. Chromium-53
  55. Chromium-54
  56. Manganese-55
  57. Iron-54 (2E)*
  58. Iron-56
  59. Iron-57
  60. Iron-58
  61. Cobalt-59
  62. Nickel-58 (2E)*
  63. Nickel-60
  64. Nickel-61
  65. Nickel-62
  66. Nickel-64
  67. Copper-63
  68. Copper-65
  69. Zinc-64 (2E)*
  70. Zinc-66
  71. Zinc-67
  72. Zinc-68
  73. Zinc-70 (2B)*
  74. Gallium-69
  75. Gallium-71
  76. Germanium-70
  77. Germanium-72
  78. Germanium-73
  79. Germanium-74
    Germanium-76 (2B) – long-lived primordial radionuclide
  80. Arsenic-75
  81. Selenium-74 (2E)
  82. Selenium-76
  83. Selenium-77
  84. Selenium-78
  85. Selenium-80 (2B)
    Selenium-82 (2B) – long-lived primordial radionuclide
  86. Bromine-79
  87. Bromine-81
    Krypton-78 (2E) – long-lived primordial radionuclide
  88. Krypton-80
  89. Krypton-82
  90. Krypton-83
  91. Krypton-84
  92. Krypton-86 (2B)
  93. Rubidium-85
    Rubidium-87 (B) – long-lived primordial radionuclide
  94. Strontium-84 (2E)*
  95. Strontium-86
  96. Strontium-87
  97. Strontium-88
  98. Yttrium-89
  99. Zirconium-90
  100. Zirconium-91
  101. Zirconium-92
  102. Zirconium-94 (2B)*
    Zirconium-96 (2B) – long-lived primordial radionuclide (B also predicted possible)
  103. Niobium-93
  104. Molybdenum-92 (2E)*
  105. Molybdenum-94
  106. Molybdenum-95
  107. Molybdenum-96
  108. Molybdenum-97
  109. Molybdenum-98 (2B)*
    Molybdenum-100 (2B) – long-lived primordial radionuclide
    Technetium – no stable isotopes
  110. Ruthenium-96 (2E)*
  111. Ruthenium-98
  112. Ruthenium-99
  113. Ruthenium-100
  114. Ruthenium-101
  115. Ruthenium-102
  116. Ruthenium-104 (2B)
  117. Rhodium-103
  118. Palladium-102 (2E)
  119. Palladium-104
  120. Palladium-105
  121. Palladium-106
  122. Palladium-108
  123. Palladium-110 (2B)*
  124. Silver-107
  125. Silver-109
  126. Cadmium-106 (2E)*
  127. Cadmium-108 (2E)*
  128. Cadmium-110
  129. Cadmium-111
  130. Cadmium-112
    Cadmium-113 (B) – long-lived primordial radionuclide
  131. Cadmium-114 (2B)*
    Cadmium-116 (2B) – long-lived primordial radionuclide
  132. Indium-113
    Indium-115 (B) – long-lived primordial radionuclide
  133. Tin-112 (2E)*
  134. Tin-114
  135. Tin-115
  136. Tin-116
  137. Tin-117
  138. Tin-118
  139. Tin-119
  140. Tin-120
  141. Tin-122 (2B)*
  142. Tin-124 (2B)*
  143. Antimony-121
  144. Antimony-123
  145. Tellurium-120 (2E)*
  146. Tellurium-122
  147. Tellurium-123 (E)*
  148. Tellurium-124
  149. Tellurium-125
  150. Tellurium-126
    Tellurium-128 (2B) – long-lived primordial radionuclide
    Tellurium-130 (2B) – long-lived primordial radionuclide
  151. Iodine-127
    Xenon-124 (2E) – long-lived primordial radionuclide
  152. Xenon-126 (2E)
  153. Xenon-128
  154. Xenon-129
  155. Xenon-130
  156. Xenon-131
  157. Xenon-132
  158. Xenon-134 (2B)*
    Xenon-136 (2B) – long-lived primordial radionuclide
  159. Caesium-133
    Barium-130 (2E) – long-lived primordial radionuclide
  160. Barium-132 (2E)*
  161. Barium-134
  162. Barium-135
  163. Barium-136
  164. Barium-137
  165. Barium-138
    Lanthanum-138 (B, E) – long-lived primordial radionuclide
  166. Lanthanum-139
  167. Cerium-136 (2E)*
  168. Cerium-138 (2E)*
  169. Cerium-140
  170. Cerium-142 (α, 2B)*
  171. Praseodymium-141
  172. Neodymium-142
  173. Neodymium-143 (α)
    Neodymium-144 (α) – long-lived primordial radionuclide
  174. Neodymium-145 (α)*
  175. Neodymium-146 (α, 2B)*
    no mass number 147§
  176. Neodymium-148 (α, 2B)*
    Neodymium-150 (2B) – long-lived primordial radionuclide
    Promethium - no stable isotopes
  177. Samarium-144 (2E)
    Samarium-146 (α) – probable long-lived primordial radionuclide
    Samarium-147 (α) – long-lived primordial radionuclide
    Samarium-148 (α) – long-lived primordial radionuclide
  178. Samarium-149 (α)*
  179. Samarium-150 (α)
    no mass number 151§
  180. Samarium-152 (α)
  181. Samarium-154 (2B)*
    Europium-151 (α) – long-lived primordial radionuclide
  182. Europium-153 (α)*
    Gadolinium-152 (α) – long-lived primordial radionuclide (2E also predicted possible)
  183. Gadolinium-154 (α)
  184. Gadolinium-155 (α)
  185. Gadolinium-156
  186. Gadolinium-157
  187. Gadolinium-158
  188. Gadolinium-160 (2B)*
  189. Terbium-159
  190. Dysprosium-156 (α, 2E)*
  191. Dysprosium-158 (α)
  192. Dysprosium-160 (α)
  193. Dysprosium-161 (α)
  194. Dysprosium-162 (α)
  195. Dysprosium-163
  196. Dysprosium-164
  197. Holmium-165 (α)
  198. Erbium-162 (α, 2E)*
  199. Erbium-164 (α, 2E)
  200. Erbium-166 (α)
  201. Erbium-167 (α)
  202. Erbium-168 (α)
  203. Erbium-170 (α, 2B)*
  204. Thulium-169 (α)
  205. Ytterbium-168 (α, 2E)*
  206. Ytterbium-170 (α)
  207. Ytterbium-171 (α)
  208. Ytterbium-172 (α)
  209. Ytterbium-173 (α)
  210. Ytterbium-174 (α)
  211. Ytterbium-176 (α, 2B)*
  212. Lutetium-175 (α)
    Lutetium-176 (B) – long-lived primordial radionuclide (α, E also predicted possible)
    Hafnium-174 (α) – long-lived primordial radionuclide (2E also predicted possible)
  213. Hafnium-176 (α)
  214. Hafnium-177 (α)
  215. Hafnium-178 (α)
  216. Hafnium-179 (α)
  217. Hafnium-180 (α)
  218. Tantalum-180m (α, B, E, IT)* ^
  219. Tantalum-181 (α)
    Tungsten-180 (α) – long-lived primordial radionuclide (2E also predicted possible)
  220. Tungsten-182 (α)*
  221. Tungsten-183 (α)*
  222. Tungsten-184 (α)*
  223. Tungsten-186 (α, 2B)*
  224. Rhenium-185 (α)
    Rhenium-187 (B) – long-lived primordial radionuclide (A also predicted possible)
    Osmium-184 (α) – long-lived primordial radionuclide (2E also predicted possible)
    Osmium-186 (α) – long-lived primordial radionuclide
  225. Osmium-187 (α)
  226. Osmium-188 (α)
  227. Osmium-189 (α)
  228. Osmium-190 (α)
  229. Osmium-192 (α, 2B)*
  230. Iridium-191 (α)
  231. Iridium-193 (α)
    Platinum-190 (α) – long-lived primordial radionuclide (2E also predicted possible)
  232. Platinum-192 (α)*
  233. Platinum-194 (α)
  234. Platinum-195 (α)*
  235. Platinum-196 (α)
  236. Platinum-198 (α, 2B)*
  237. Gold-197 (α)
  238. Mercury-196 (α, 2E)*
  239. Mercury-198 (α)
  240. Mercury-199 (α)
  241. Mercury-200 (α)
  242. Mercury-201 (α)
  243. Mercury-202 (α)
  244. Mercury-204 (2B)
  245. Thallium-203 (α)
  246. Thallium-205 (α)
  247. Lead-204 (α)*
  248. Lead-206 (α)*
  249. Lead-207 (α)*
  250. Lead-208 (α)*
    Bismuth ^^ and above –
    no stable isotopes
    no mass number 209 and above
    Bismuth-209 (α) – long-lived primordial radionuclide
    Thorium-232 (α, SF) – long-lived primordial radionuclide (2B also predicted possible)
    Uranium-235 (α, SF) – long-lived primordial radionuclide
    Uranium-238 (α, 2B, SF) – long-lived primordial radionuclide
    Plutonium-244 (α, SF) – probable long-lived primordial radionuclide (2B also predicted possible)

Abbreviations for predicted unobserved decay:[12][2][11]

α for alpha decay, B for beta decay, 2B for double beta decay, E for electron capture, 2E for double electron capture, IT for isomeric transition, SF for spontaneous fission, * for the nuclides whose half-lives have lower bound. Double beta decay has only been listed when beta decay is not also possible.

^ Tantalum-180m is a "metastable isotope", meaning it is an excited nuclear isomer of tantalum-180. See isotopes of tantalum. However, the half-life of this nuclear isomer is so long that it has never been observed to decay, and it thus is an "observationally stable" primordial nuclide, a rare isotope of tantalum. This is the only nuclear isomer with a half-life so long that it has never been observed to decay. It is thus included in this list.

^^ Bismuth-209 was long believed to be stable, due to its half-life of 2.01×1019 years, which is more than a billion times the age of the universe.

§ Europium-151 and samarium-147 are primordial nuclides with very long half-lives of 4.62×1018 years and 1.066×1011 years, respectively.

See also

[edit]

References

[edit]
  1. ^ "DOE explains ... Isotopes". Department of Energy, United States. Archived from the original on 14 April 2022. Retrieved 11 January 2023.
  2. ^ a b c Belli, P.; Bernabei, R.; Danevich, F. A.; et al. (2019). "Experimental searches for rare alpha and beta decays". European Physical Journal A. 55 (8): 140–1–140–7. arXiv:1908.11458. Bibcode:2019EPJA...55..140B. doi:10.1140/epja/i2019-12823-2. ISSN 1434-601X. S2CID 201664098.
  3. ^ Sonzogni, Alejandro. "Interactive Chart of Nuclides". National Nuclear Data Center: Brook haven National Laboratory. Archived from the original on 2018-10-10. Retrieved 2008-06-06.
  4. ^ Various (2002). Lide, David R. (ed.). Handbook of Chemistry & Physics (88th ed.). CRC. ISBN 978-0-8493-0486-6. OCLC 179976746. Archived from the original on 2017-07-24. Retrieved 2008-05-23.
  5. ^ Kelkar, N. G.; Nowakowski, M. (2016). "Signature of the N = 126 shell closure in dwell times of alpha-particle tunneling". Journal of Physics G: Nuclear and Particle Physics. 43 (105102). arXiv:1610.02069. Bibcode:2016JPhG...43j5102K. doi:10.1088/0954-3899/43/10/105102.
  6. ^ "WWW Table of Radioactive Isotopes". [permanent dead link‍]
  7. ^ Marcillac, Pierre de; Noël Coron; Gérard Dambier; Jacques Leblanc & Jean-Pierre Moalic (2003). "Experimental detection of α-particles from the radioactive decay of natural bismuth". Nature. 422 (6934): 876–878. Bibcode:2003Natur.422..876D. doi:10.1038/nature01541. PMID 12712201. S2CID 4415582.
  8. ^ de Carvalho H. G., de Araújo Penna M. (1972). "Alpha-activity of 209Bi". Lett. Nuovo Cimento. 3 (18): 720–722. doi:10.1007/BF02824346.
  9. ^ "NNDC – Atomic Masses". www.nndc.bnl.gov. Archived from the original on 2019-01-11. Retrieved 2009-01-17.
  10. ^ a b c d Nucleonica website
  11. ^ a b Tretyak, V.I.; Zdesenko, Yu.G. (2002). "Tables of Double Beta Decay Data — An Update". At. Data Nucl. Data Tables. 80 (1): 83–116. Bibcode:2002ADNDT..80...83T. doi:10.1006/adnd.2001.0873.
  12. ^ "Nucleonica :: Web driven nuclear science".

Book references

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