Which of the following best describes how radioactive isotopes differ from stable isotopes?

• A. Radioactive isotopes have more protons than stable isotopes.
• B. Radioactive isotopes have the same number of neutrons as stable isotopes.
• C. Radioactive isotopes have unstable nuclei that spontaneously decay, emitting radiation.
• D. Radioactive isotopes do not exist naturally.

Answer: (C)

Verified step by step guidance

1. Understand that isotopes of an element have the same number of protons but differ in the number of neutrons.
2. Recognize that stable isotopes have nuclei that do not change or decay over time, meaning their nuclear composition remains constant.
3. Know that radioactive isotopes have unstable nuclei that spontaneously undergo nuclear decay, emitting radiation such as alpha, beta, or gamma rays.
4. Note that the difference between radioactive and stable isotopes is not the number of protons, but the stability of their nuclei due to neutron-to-proton ratio.
5. Also understand that radioactive isotopes can exist naturally or be artificially produced, so the statement that they do not exist naturally is incorrect.