In order to determine the lattice formation energy for KCl, the following data are provided: Ionization energy of K(g) = 425 kJ/mol
Electron affinity of Cl(g) = –349 kJ/mol
Energy to sublime K(s) = 89 kJ/mol
Bond energy of Cl2(g) = 240 kJ/mol
ΔHf for K(s) + ½Cl2(g) → KCl(s) = –438 kJ/mol

Sort the steps of the Born–Haber cycle according to the sign of the energy change associated with each.

K(g) → K^(g)+ e
K^+(g) + Cl^- →KCl(s)
K(s) + K(g)