This area chart displays the neutron-to-proton ratio (N/Z) across all elements. Light elements have N/Z close to 1, while heavy elements approach ratios of 1.5 or higher.

The increasing N/Z ratio is crucial for nuclear stability. In light nuclei, the strong nuclear force easily overcomes proton repulsion, so roughly equal numbers work. However, as atomic number increases, additional neutrons are needed to provide extra binding without adding more repulsive positive charge.