Q2(b). Second ionisation energy of sodium

The lattice energies (U₀) for the formation of NaCl and hypothetical NaCl₂ from Cl₂ gas and Na metal are −757 kJ mol⁻¹ and −2180 kJ mol⁻¹, and enthalpies of formation (ΔH_f) are −381 kJ mol⁻¹ and +2530 kJ mol⁻¹, respectively. From these data, calculate the 2nd ionization energy of Na. (Given that ΔH_EA for Cl and ΔH_atomization for Cl₂ → 2Cl are −349 and +242 kJ mol⁻¹, respectively.)