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. R = R₀ A¹/³ . A = 200 , A¹/³ = 200¹/³ ≈ 5.85 . R = 1.2 × 10⁻¹⁵ × 5.85 ≈ 7.0 × 10⁻¹⁵ m . 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 7.0 × 10⁻¹⁵ m, consistent with Bohr model and nuclear binding energy systematics.