Stable nuclide
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.

Stable nuclide

Section Title: Summary table for numbers of each class of nuclides
Table Section Text: 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.

Type of nuclide by stability class	Number of nuclides in class	Running total of nuclides in all classes to this point	Notes

Theoretically stable to all but proton decay	90	90	Includes first 40 elements. If protons decay, then there are no stable nuclide.

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	56	146	All nuclides that are possible 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. Considered stable until radioactivity confirmed.	106	252	Total is the observationally stable nuclides.

Radioactive primordial nuclides.	34	286	Includes Bi, Th, U.

Radioactive nonprimordial, but naturally occurring on Earth.	~61 significant	~347 significant	Cosmogenic nuclides from cosmic rays; daughters of radioactive primordials such as francium, etc.

Sentence(s)

There were a total of 252 "stable" nuclides.

final_sentence: There were a total of 252 "stable" nuclides.