Provide the steps and their corresponding enthalpies for the formation of $NaCl$ (sodium chloride).

The formation of $NaCl$ involves the following steps:
$1$. Ionization of sodium: $Na_{(g)} \rightarrow Na_{(g)}^{+} + e^{-}; \Delta_{i}H = 495.8 \, kJ \, mol^{-1}$
$2$. Electron gain by chlorine: $Cl_{(g)} + e^{-} \rightarrow Cl_{(g)}^{-}; \Delta_{eg}H = -348.7 \, kJ \, mol^{-1}$
$3$. Lattice formation: $Na_{(g)}^{+} + Cl_{(g)}^{-} \rightarrow NaCl_{(s)}; \Delta_{L}H = -788 \, kJ \, mol^{-1}$
$4$. The total enthalpy of formation is given by: $\Delta_{f}H(NaCl) = \Delta_{i}H + \Delta_{eg}H + \Delta_{L}H$
$\Delta_{f}H(NaCl) = 495.8 - 348.7 - 788 = -640.9 \, kJ \, mol^{-1}$