Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
For lithium fluoride, in kJ/mol: sublimation of lithium , half the bond enthalpy of fluorine , ionisation of lithium , electron gain of fluorine , and lattice enthalpy . Find the enthalpy of formation of LiF.
Born-Haber cycle: enthalpy of formation sublimation half the bond enthalpy ionisation enthalpy electron gain enthalpy lattice enthalpy. The lattice enthalpy is the energy needed to separate one mole of an ionic solid into its gaseous ions. It grows with the charges of the ions and as the ions get smaller.
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The gaseous ions. kJ/mol.
Step 2. Formation. kJ/mol.
Answer: kJ/mol.
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