Practice question

**Energy in hydrogen** total E_n = -13.6/n² eV, kinetic K = +13.6/n² eV, potential U = -27.2/n² eV, ratio K/U = -1/2, total negative indicates bound, zero at ionization, negative total means electron bound, requires energy to free. For n=4 E=-0.85 eV, U=-1.7 eV, K=0.85 eV, potential energy twice total negative. E = m c² . m = 0.05 × 10⁻³ kg = 5 × 10⁻⁵ kg , c² = 9 × 10¹⁶ m²/s² . E = 5 × 10⁻⁵ × 9 × 10¹⁶ = 4.5 × 10¹² J . Using E_n = -13.6/n² eV, r_n = n² a₀, L = n h/2π, R =