Lattice Energy & Born–Haber Cycles (A2)

Lattice energy

The lattice energy $\Delta H_{\text{latt}}^{\ominus}$ is the enthalpy change when one mole of an ionic solid is formed from its gaseous ions under standard conditions:

$$\text{Na}^{+}(g) + \text{Cl}^{-}(g) \rightarrow \text{NaCl}(s) \qquad \Delta H_{\text{latt}}^{\ominus}$$

It is always exothermic (ions of opposite charge attracting). It cannot be measured directly, so it is found indirectly using a Born–Haber cycle (an application of Hess's law).