Final answer:
The stability of nuclei is determined by the neutron-to-proton ratio, with light elements needing ratios close to 1:1 and heavier elements requiring ratios up to about 1.5:1 for stability. The correct option is A) Neutron-to-proton ratio.
Step-by-step explanation:
The ratio that determines the stability of nuclei is the neutron-to-proton ratio. This ratio is crucial because it affects the nuclear binding energy and the balance between the strong nuclear force and electrostatic repulsion within a nucleus. As atoms increase in atomic number, they require a higher neutron-to-proton ratio for stability.
Isotopes of light elements like hydrogen have a ratio that can be close to 1:1, whereas heavier elements like lead have a ratio that increases, up to about 1.5:1.
The neutron-to-proton ratio is an important predictor in determining if a nucleus will be stable or radioactive. Interestingly, all elements with an atomic number greater than 83 are unstable regardless of their neutron-to-proton ratio, implying that the sheer number of protons leads to instability due to increased repulsion. The correct option is A) Neutron-to-proton ratio.