Write an equation to represent the first ionisation energy of caesium.

Calculate the lattice energy for sodium chloride, given that:

$∆{{\mathrm{H}}_{\mathrm{f}}}^{\circ }\left[\mathrm{NaCl}\right]=-411 \mathrm{kJ} {\mathrm{mol}}^{-1}$

$∆{{\mathrm{H}}_{\mathrm{at}}}^{\circ }\left[\mathrm{Na}\right]=+107 \mathrm{kJ} {\mathrm{mol}}^{-1}$

$∆{{\mathrm{H}}_{\mathrm{at}}}^{\circ }\left[\mathrm{Cl}\right]=+122 \mathrm{kJ} {\mathrm{mol}}^{-1}$

${\mathrm{IE}}_1\left[\mathrm{Na}\right]=+496 \mathrm{kJ} {\mathrm{mol}}^{-1}$

${\mathrm{EA}}_1\left[\mathrm{Cl}\right]=-348 \mathrm{kJ} {\mathrm{mol}}^{-1}$