A simple ionic model is revisited. The model starts with the calculation of lattice energy and thus the thermochemical radii of the ions. These radii allow the calculation of other lattice energies and through a Born-Haber cycle to obtain the enthalpy of formation. By using literature available for experimental data, the model was tested to see if it can provide reliable enthalpies of formation values. As presented in this contribution, the method only applies to binary compounds with both simple and complex ions. As examples of the usefulness of this approach, enthalpies of formation of unmeasured crystalline ionic liquids (Hmim(+), C(2)mim(+), C(4)mim(+) and NH4+ families) and lanthanide (II) halides were determined. The latter ones were used to address the stability of lanthanide halides in states II and III. (C) 2014 Elsevier Ltd. All rights reserved.