Final answer:
The stability of a nuclide is determined by the neutron-to-proton ratio, which ideally is 1:1 for light elements and increases to about 1.5:1 for heavy elements. Nuclei with imbalanced ratios undergo decay processes to achieve stability.
Step-by-step explanation:
The proton to neutron ratio required to have a stable nuclide varies depending on the element's atomic number. For lighter elements (with lower atomic numbers), a neutron-to-proton ratio of approximately 1:1 is ideal for stability, like in the case of Carbon-12. As the atomic number increases, the stable ratio gradually increases to about 1.5:1 in heavier elements. For example, lead-206 is considered stable with a ratio of 1.51 to 1. Notably, all elements with an atomic number greater than 83 are unstable and radioactive. Nuclei with low neutron-to-proton ratios decay via positron emission or electron capture to achieve stability. Stable isotopes, such as Helium, Boron-10, Calcium-40, and the 'double magic' Lead-208, have neutron-to-proton ratios that adhere to this rule for their respective atomic numbers.