The ionization energy for sodium is 5.1 eV and electron affinity of bromine is 3.5 eV. Calculate the largest separation between Na and Br (as neutral atoms) for which they remain a bound molecule. Hint: the molecule will remain bound if the Coulomb energy of ions is lower than energy of neutral atoms. At the dissociation distance, the Coulomb energy between the ions is equal to the energy needed to create them our of neutral atoms: