Practice question

**Nuclear size** order 10⁻¹⁵ m femtometer, atomic size 10⁻¹⁰ m, ratio 10⁵, nucleus contains protons and neutrons bound by strong force, density independent of A indicates incompressibility, R₀ determined from electron scattering experiments. Radius ratio = (R₁/R₂) = (R₀ A₁¹/³/R₀ A₂¹/³) = ( (A₁/A₂) )¹/³ . A₁ = 27 , A₂ = 125 . (27/125) = 0.216 , (0.216)¹/³ ≈ 0.6 . 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 0.6, consistent with Bohr model and nuclear binding energy systematics.