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