Aradioactive isotope is an isotope that a) decays. b) has the same atomic mass but a different atomic number than the common variant of the element. c) has more protons than the common variant of the element. d) is stable.

A) Decays

Explanation:

One element is considered an isotope of another when they have the same number of protons but a different number of neutrons.

Radioactive isotopes are unstable and release highly charged electromagnetic particles, and of course they emit radiation.

At this point they eventually turn into other types of elements by radiation emission due to its unstable core and this process is called radioactive decay or transmutation.

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