text: The primordial radionuclides have been included for comparison; they are italicised and offset from the list of stable nuclides proper.
  Abbreviations for predicted unobserved decay:
  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.
  ^ 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.
  ^^ Bismuth-209 had long been believed to be stable, due to its half-life of 2.01 · 10 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 · 10 years and 1.066 · 10 years, respectively.