The correct statement about stable isotopes is:
A stable nucleus has a similar number of protons and neutrons.
This is because stable isotopes generally have a balanced ratio of protons to neutrons, which contributes to the stability of the nucleus. The other statements are incorrect:
- Isotopes can be stable or unstable; not all isotopes are radioactive.
- There are naturally occurring isotopes that are stable.
- Isotopes with more neutrons than protons can be either stable or unstable; it depends on the specific isotope.