Definitions for

**"Born-Haber cycle"**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) â†’ M+X-(s) Î”HL The standard enthalpy of formation of the ionic solid is the enthalpy of the reaction M(s) + 1/2X2(g) â†’ M+X-(s) Î”Hf 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) â†’ M(g) Î”H1 2) Atomization of the nonmetal 1/2X2(g) â†’ X(g) Î”H2 3) Ionization of the metal M(g) â†’ M+(g) + e- Î”H3 This is obtained from the ionization potential. 4) Ionization of the nonmetal X(g) + e- â†’ X-(g) Î”H4 This is electron affinity. 5) Formation of the ionic solids M+(g) + X-(g) â†’ M+X-(s) Î”HL Equation the enthalpies gives Î”Hf = Î”H1 + Î”H2 + Î”H3 + Î”H4 + Î”HL from which Î”HL can be found.

a very special type of Hess' Law cycle

electron affinity ideal gas Nernst equation simple cubic structure