Since the process is endothermic, therefore ionisation enthalpy is taken as a positive quantity. Since energy is required for the process (endothermic), therefore, is taken as a positive quantity. The formation of ionic crystal from its elements by applying different thermochemical quantities is called Born-Haber cycle.Ĭonsider the enthalpy change during the formation of ionic solid MX from its elements M and X.įormation of ionic solid MX may be done by two different methods:
In 1919, Born and Haber proposed a method in which lattice enthalpy of an ionic crystal is related to certain thermodynamic parameters.
