Editing Radionuclide (section)

==Summary table for classes of nuclides, stable and radioactive==
Following is a summary table for the [[list of nuclides|list of 989 nuclides]] with half-lives greater than one hour. A total of 251 nuclides have never been observed to decay, and are classically considered stable. Of these, 90 are believed to be absolutely stable except to [[proton decay]] (which has never been observed), while the rest are "[[observationally stable]]" and theoretically can undergo radioactive decay with extremely long half-lives.

The remaining tabulated radionuclides have half-lives longer than 1 hour, and are well-characterized (see [[list of nuclides]] for a complete tabulation). They include 30 nuclides with measured half-lives longer than the estimated age of the universe (13.8&nbsp;billion years<ref>{{cite web |title = Cosmic Detectives |url=http://www.esa.int/Our_Activities/Space_Science/Cosmic_detectives
|publisher = The European Space Agency (ESA) |date = 2013-04-02 |access-date = 2013-04-15}}</ref>), and another four nuclides with half-lives long enough (>&nbsp;100&nbsp;million years) that they are radioactive [[primordial nuclide]]s, and may be detected on Earth, having survived from their presence in interstellar dust since before the formation of the [[Solar System]], about 4.6 billion years ago. Another 60+ short-lived nuclides can be detected naturally as daughters of longer-lived nuclides or cosmic-ray products. The remaining known nuclides are known solely from artificial [[nuclear transmutation]].

Numbers are not exact, and may change slightly in the future, as "stable nuclides" are observed to be radioactive with very long half-lives.

This is a summary table<ref>Table data is derived by counting members of the list; see [[WP:CALC]]. References for the list data itself are given below in the reference section in [[list of nuclides]]</ref> for the 989 nuclides with half-lives longer than one hour (including those that are stable), given in [[list of nuclides]].
{| class="wikitable sortable" width="100%"
! width="300" |Stability class
! Number of nuclides
! [[Running total]]
! Notes on running total
|-
| align="left"| Theoretically stable to all but [[proton decay]]
| align="center"| 90
| align="center"| 90
| Includes first 40 elements. Proton decay yet to be observed.
|-
| Theoretically stable to [[alpha decay]], [[beta decay]], [[isomeric transition]], and [[double beta decay]] but not [[spontaneous fission]], which is possible for "stable" nuclides ≥ [[niobium-93]]
| align="center"| 56
| align="center"| 146
| All nuclides that are ''possibly'' completely stable (spontaneous fission has never been observed for nuclides with mass number < 232).
|-
| Energetically unstable to one or more known decay modes, but no decay yet seen. All considered "stable" until decay detected.
| align="center"| 105
| align="center"| 251
| Total of classically [[stable nuclide]]s.
|-
| Radioactive [[primordial nuclide]]s.
| align="center"| 35
| align="center"| 286
| Total primordial elements include [[uranium]], [[thorium]], [[bismuth]], [[rubidium-87]], [[potassium-40]], [[tellurium-128]] plus all stable nuclides.
|-
| Radioactive nonprimordial, but naturally occurring on Earth.
| align="center"| 61
| align="center"| 347
| [[Carbon-14]] (and other isotopes generated by [[cosmic rays]]) and daughters of radioactive primordial elements, such as [[radium]], [[polonium]], etc. 41 of these have a half life of greater than one hour.
|-
| Radioactive synthetic half-life ≥ 1.0 hour). Includes most useful [[radiotracer]]s.
| align="center"| 662
| align="center"| 989
| These 989 nuclides are listed in the article [[List of nuclides]].
|-
| Radioactive synthetic (half-life < 1.0 hour).
| align="center"| >2400
| align="center"| >3300
| Includes all well-characterized synthetic nuclides.
|-
|}