text: 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.
  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. The mean number of stable isotopes for elements which have at least one stable isotope is 251/80 = 3.1375.