Born-Haber NaCl: U_lattice = -787 kJ/mol (ΔH_f = -410 closure)

Sympy-exact symbolic witness of the Born-Haber-cycle closure for NaCl: solve for U_lattice from experimental step enthalpies. Inputs (kJ/mol, standard experimental values): ΔH_sub(Na) = +108, ½·ΔH_diss(Cl₂) = +122, IE(Na) = +496, −EA(Cl)…