The enthalpy change for the ionization of lithium with a first ionization energy of 520 kJ/mol is equal to the ionization energy itself. Ionization energy is the energy required to remove an electron from an atom or ion, and the enthalpy change represents the energy change during this process. Therefore, the enthalpy change for the ionization of lithium is +520 kJ/mol. The positive sign indicates that the process is endothermic, meaning it requires energy to be inputted.