The enthalpy of sublimation, first ionisation enthalpy and hydration enthalpy of the gaseous ion (all in $\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$) are: Li (159, 520, $-519$), Na (107, 496, $-406$), K (89, 419, $-322$). For the process $\mathrm{M}(\mathrm{s})\to \mathrm{M}{}^{+}(\mathrm{aq})+\mathrm{e}{}^{-}(\mathrm{g})$, which metal has the least endothermic enthalpy change and what is it?

1. AK, $+186\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$
2. BLi, $+1198\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$
3. CLi, $+160\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$
4. DNa, $+197\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$