Band of Stability
The region on a plot of neutron number against proton number within which stable nuclides are found.
Unit
Dimensionless
In depth
The band follows the line N = Z for light elements but curves upward for heavier ones, reaching a ratio near 1.5 as extra neutrons are needed to dilute proton repulsion. Nuclides above the band undergo beta-minus decay and those below it positron emission or electron capture.
Examples in the real world
Carbon-12 sits on the band with N = Z; lead-208 sits far above it with 126 neutrons to 82 protons.