Relationship of thermodynamic data with Periodic Law

Abstract

Abstract Relationships between the various physical and chemical properties of isostructural compounds take place according to the Periodic Table that is a fundamental basis of Chemistry. The systematization of this approach, data vs. the Periodic Table, will contribute to further development of the solid state chemistry theory. The lanthanides and the actinides make up the f block of the Periodic Table. The lanthanides are the elements produced as the 4f sublevel is filled with electrons and the actinides are formed while filling the 5f sublevel. In this paper, we analyze some classes of compounds formed by the lanthanides with other elements of the Periodic Table, which can count into the thousands of binary compounds. The special place of lanthanides in the Periodic System of Elements made it possible to establish strict nonlinear relationships between the standard entropy and the lanthanide atomic number of the compounds Ln 2 X 3 (X = O, S, Se, Te), LnN, LnB4, and LnF3 in the solid state. This relationship, based on tetrad-effect, can be applied to other physical and chemical properties of the isostructural compounds. The thermodynamic properties of actinides have been studied much less than lanthanides, but the similarity of physicochemical properties makes it possible for us to estimate, with sufficient accuracy, unexplored properties using fundamental laws. One of these laws is the tetrad-effect concept that is an effective tool to predict missing thermodynamic values for lanthanide and actinide compounds and to rationally plan experiments.