LATTICE ENTHALPIES OF IONIC HALIDES, HYDRIDES, OXIDES, AND SULFIDES - 2ND-ELECTRON AFFINITIES OF ATOMIC OXYGEN AND SULFUR

Lattice enthalpies of ionic compounds are calculated using the equation: ΔHL (ionic) = Aσ-1/m se-(m-1)/m where A is the attractive constant, se is internuclear separation, σ is a constant distance, and m is a real positive even integer. For crystalline ionic halides at 298 K, m = 6 and σ = 4.80 Å. For crystalline ionic hydrides, oxides, and sulfides at 298 K, m = 4 and σ = 5.81 Å. Standard molar enthalpies of formation of gaseous bivalent anions at 298 K are ΔHf(O2-, g, 298 K) 697(±10), ΔHf(S2-, g, 298 K) 483(±10) kJ mol-1. The second molar electron affinities of atomic oxygen and sulfur at zero temperature are E2(O, g, 0 K) 599(±10) and E2(S, g, 0 K) 416(±10) kJ mol-1, respectively.