Practice question

**Stability** belt of stability N≈Z for light, N>Z for heavy due to Coulomb, beyond leads to alpha decay, fission, stability requires balance, nuclear force saturated explains constant density and BE/A. The nuclear force is charge-independent, acting equally between neutron-neutron, proton-neutron, and proton-proton pairs, as it is a fundamental property unrelated to electric charge. Using E_n = -13.6/n² eV, r_n = n² a₀, L = n h/2π, R = R₀ A^¹/³, BE = Δm c² and 1 u = 931.5 MeV, evaluation yields It is charge-independent, consistent with Bohr model and nuclear binding energy systematics.