Born-Haber cycle is a cycle of reactions used for calculating the lattice energies of ionic crystalline solids. For a compound MX, the lattice energy is the enthalpy of the reaction M+(g) + X-(g) → M+X-(s) ΔHL The standard enthalpy of formation of the ionic solid is the enthalpy of the reaction M(s) + 1/2X2(g) → M+X-(s) ΔHf The cycle involves equating this enthalpy (which can be measured) to the sum of the enthalpies of a number of steps proceeding from the elements to the ionic solid. The steps are: 1) Atomization of the metal M(s) → M(g) ΔH1 2) Atomization of the nonmetal 1/2X2(g) → X(g) ΔH2 3) Ionization of the metal M(g) → M+(g) + e- ΔH3 This is obtained from the ionization potential. 4) Ionization of the nonmetal X(g) + e- → X-(g) ΔH4 This is electron affinity. 5) Formation of the ionic solids M+(g) + X-(g) → M+X-(s) ΔHL Equation the enthalpies gives ΔHf = ΔH1 + ΔH2 + ΔH3 + ΔH4 + ΔHL from which ΔHL can be found.
a very special type of Hess' Law cycle
electron affinity ideal gas Nernst equation simple cubic structure
This is a thermochemical cycle which describes the formation of an ionic solid in terms of the formation of the gaseous ions from the standard states of the species involved, and from which the lattice energy may be calculated.
A series of reactions (and accompanying enthalpy changes) which, when summed, represents the hypothetical one-step reaction by which elements in their standard states are converted into crystals of ionic compounds (and the accompanying enthalpy changes.)
The Born-Haber Cycle is an approach to analyzing reaction energies, it was named after and developed by the two German scientists Max Born and Fritz Haber.