Divalent ionic crystals Barium oxide has the NaC1 structure. Estimate the cohesive energies per molecule of the hypothetical crystals Ba⁺ O^– and Ba⁺⁺ O^{– –} referred to separated neutral atoms. The observed nearest-neighbor inter nuclear distance is R₀ = 2.76 A; the first and second ionization potentials of Ba are 5.19 and 9.96eV; and the electron affinities of the first and second electrons added to the neutral oxygen atom are 1.5 and —9.0eV. The first electron affinity of the neutral oxygen atom is the energy released in the reaction O + e → O^–.The second electron affinity is the energy released in the reaction O^– + e → O^{– –}. Which valence state do you predict will occur? Assume R₀ is the same for both forms, and neglect the repulsive energy.