Question

What radioactive isotopes are naturally occurring?

Answer 1

This is a list of all the naturally occurring elements which either have no stable isotopes, or have at least one naturally occurring isotope that is radioactive.

Potassium `K^19`
Technetium `Tc^43`
Cadmium `Cd^48`
Promethium `Pm^61`
Polonium `Po^84`
Astatine `At^85`
Radon `Rn^86`
Francium `Fr^87`
Radium `Ra^86`
Actinium `Ac^89`
Uranium `U^92`

93-118 are not naturally occurring but are radioactive.
110-118 have not been named yet.