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All of the elements have some isotopes that are radioactive ( radioisotopes ), although not all of these radioisotopes occur naturally.

The radioisotopes typically decay into other elements upon radiating an alpha or beta particle.

If an element has isotopes that are not radioactive, they are termed " stable.

" All of the known stable isotopes occur naturally ( see primordial isotope ).

The many radioisotopes that are not found in nature have been characterized from being artificially made.

Certain elements have no stable isotopes and are composed only of radioactive isotopes: specifically the elements without any stable isotopes are technetium ( atomic number 43 ), promethium ( atomic number 61 ), and all observed elements with atomic numbers greater than 82.