Born Haber Cycle

The Born-Haber cycle is a famous cycle of chemical reactions, first developed by Max Born and the German chemist Fritz Haber in 1917 .

The Born-Haber cycle involves the formation of an ionic compound from the reaction of a metal (often a group I or group 2 element) with a non-metal (like gaseous halogens, oxygen, sulfur or others). Born-Haber cycles are used primarily as a means of calculating lattice enthalpies, which cannot otherwise be measured directly.

The lattice enthalpy is the formation of the ionic compound from gaseous ions. Some chemists define it as the energy to break the ionic compound into gaseous ions. The former definition is invariably Exothermic and the latter is Endothermic .

A Born-Haber cycle calculates the lattice enthalpy by comparing the Standard Enthalpy Change Of Formation of the ionic compound (from the elements) to the enthalpy required to make gaseous ions from the elements. This is an application of Hess's Law .

It is this latter calculation that is complex. To make gaseous ions from elements it is necessary to atomise the elements (turn each into gaseous atoms) and then to ionise the atoms. If the element is normally a molecule then we have to consider its Bond Dissociation Enthalpy (see also Bond Energy . The energy involved in removing electron to make a cation is called the Ionization Energy . The enthalpy of adding electrons to an atom to make it an anion is called the Electron Affinity .

See Ionic Crystal and Ionic Compound for the basics. Ionic Liquids (see also Ionic Liquid ) are novel and interesting.

Information About

Born Haber Cycle