Laws of change of thermodynamic properties of 3d compounds — elements(II) — fluorides and chlorides

Abstract

The possibility of using a semi-empirical method for the evaluation of the thermodynamic properties of fluorides and chlorides 3d metals in the oxidation state (+2) and the establishment of regularities of their changes depending on the nature of the metal cations and anions is presented. The method developed by Poluektov N. S. and his colleagues takes into account the peculiarities of the electronic structure of 3d metals and their influence on the determined properties of the compounds. The calculated values of the thermodynamic characteristics — enthalpy of formation, entropy and heat capacity – for the more studied of the chlorides 3d metal compounds are in good agreement with the reference. This demonstrates the competence of the method for the calculation and evaluation of unknown characteristics of 3d metals. The most complete information about the thermodynamic characteristics of fluorides and chlorides 3d metals defined and/or refined by this method are obtained. It is found that the patterns of variation of these properties depending on the nature of the cations and anions are complex. The curves of these patterns which are dependent on the nature of metal are separated by subgroups based on the partial (for manganese ions) or full (for zinc ions) filling of 3d-orbitals by electrons. According to characteristics, copper and chromium compounds fall outside the general pattern. The equations expressing these curve patterns for subgroups 3d metals are here compiled.