If an isotope falls outside the Belt of Stability then it is unstable (radioactive) and will spontaneously undergo nuclear reactions.

If an isotope falls outside the Belt of Stability then it is unstable (radioactive) and will spontaneously undergo nuclear reactions.

• A. Stable
• B. Unstable
• C. Radioactive but stable
• D. Depends on temperature

Answer: (B)

Outside the Belt of Stability means the neutron-to-proton ratio is not at the value that minimizes the nucleus’s energy. Nuclei with too many or too few neutrons relative to protons are energetically unstable and will decay spontaneously toward a more stable configuration. This decay is what we call radioactive, as the nucleus emits particles or radiation to reach a lower-energy state. Temperature doesn’t determine stability, so conditions like heat don’t make an unstable nucleus become stable. The correct classification is that the isotope is unstable and radioactive.

Outside the Belt of Stability means the neutron-to-proton ratio is not at the value that minimizes the nucleus’s energy. Nuclei with too many or too few neutrons relative to protons are energetically unstable and will decay spontaneously toward a more stable configuration. This decay is what we call radioactive, as the nucleus emits particles or radiation to reach a lower-energy state. Temperature doesn’t determine stability, so conditions like heat don’t make an unstable nucleus become stable. The correct classification is that the isotope is unstable and radioactive.