Choose the 2 reasons some atoms are radioactive. a. the number of additional neutrons of an isotope is too large b. the nucleus itself is too large c. atomic numbers < 83 o d. the number of additional neutrons of an isotope is too small e. the nucleus itself is too small

The correct options are: a. the number of additional neutrons of an isotope is too large; d. the number of additional neutrons of an isotope is too small

Explanation:

The chemical elements that have the same number of protons in the nucleus but different number of neutrons are known as isotopes. Isotopes can be stable or unstable.

The isotope having an unstable nucleus, due to the presence of additional neutrons in the nucleus of the atom, is known as a radioisotope.

Also, chemical elements that have atomic number greater than 83 have unstable nuclei and thus they are called radioisotopes.