Comparison of the thermochemistry of the difluorides and potassium hexafluorometallates(IV) of the elements of the germanium triad with that of the elements of the nickel triad : a study of the inert-pair effect

Abstract

An attempt has been made to resolve the conflict between the classical interpretation of the development of a valency two less than the group valency in Groups 3B–8B of the Periodic Table and contemporary criticism of it. This has been done by analysing the enthalpy of process (1) for M = Ni, Pd, Pt and Ge, Sn, Pb. The following standard enthalpies of formation at 25 °C were determined by K₂MF₆(c)→ MF₂(c)+ 2KF(c)+ F₂(g)(1) solution calorimetry: PdF₂(c), –495; SnF₂(c), –672; PtF₄(c), –681; K₂NiF₆(c), –1 963; K₂PdF₆(c), –2 040; K₂PtF₆(c), –2 055; K₂GeF₆(c), –2 603; K₂SnF₆(c), –2 575; K₂PbF₆(c), –2 209 kJ mol^–1. Other data were taken from the literature or were estimated. From the analysis it was concluded that the classical explanation of the development of a valency of two in Group 4B, that a pair of valency electrons becomes inert, is essentially correct.