Stable isotope

A stable isotope is one which is not radioactive.

List of stable isotopes

There are exactly 80 elements which have at least 1 stable isotope. As of September 2007, there were 244 known stable isotopes. Xenon is the only element which has 9 stable isotopes. Tin has 10 stable isotopes, more than any other element. There is no element with exactly 8 stable isotopes. Every element from hydrogen to lead has at least one stable isotope with the exceptions of technetium and promethium; elements with more than 82 protons only have radioactive isotopes, and can still occur naturally if their half-lives are of a sufficient order of magnitude, or because they occur in a decay chain of another radioactive isotope. It wasn't until 2003 that bismuth-209 was shown to be radioactive.^[1] All stable isotopes are the ground states of nuclei, excluding tantalum-180, which is the excited level (the ground state of this nucleus is radioactive), but its decay is extremely strongly forbidden by spin-parity selection rules.