The energy required to break a given bond of some specific compound by heterolysis. For the dissociation of a neutral molecule AB in the gas phase into A⁺ and B⁻ the heterolytic bond-dissociation energy D(A⁺B⁻) is the sum of the bond dissociation energy, D(A–B), and the adiabatic ionization energy of the radical A· minus the electron affinity of the radical B·.