Born-Haber Cycle

The Born-Haber cycle is an application of Hess's law that breaks down the formation of an ionic compound into a series of individual steps: sublimation of the solid metal (S), bond dissociation of the diatomic nonmetal (B), ionization of the gaseous metal (I), addition of an electron to the nonmetal (A), and formation of the lattice (U). Each of these steps has an associated enthalpy change: sublimation energy (S), bond dissociation energy (B), ionization energy (I), and electron affinity (A). The lattice energy (U) is often a calculated value rather than measured directly. The sum of these enthalpies gives the overall enthalpy change for the formation of the ionic compound from its elements in their standard states. It is commonly used in physical chemistry to determine the lattice energy of ionic solids.