Systematics and anomalies

Abstract

Systematics is a powerful tool and anomalies thereof are extremely helpful in our comprehension of the behaviors of the rare earth elements and in particular, the lanthanides. It is shown that a greater knowledge of the lanthanide elements is obtained if information is available on the corresponding Sc and Y compounds, and these are also included in the systematic evaluation of the property, than if the lanthanide data are used by themselves. Initially, the behaviors of the pure elements are examined, and then in turn systematics is applied to solid solution alloys (especially H in R), the melting behavior and heats (free energies) of formation of rare earth compounds, and finally aqueous solutions (stability constants of complexes). All of these data indicate that 4f hybridization with the valence electrons (5d, 6s) of the lanthanide and the non-rare earth element in an alloy or compound occurs. The most striking evidence for 4f bonding is seen in the H dissolved in R solid solution alloys. A new method for predicting heats (free energies) of formation of the lanthanide element compounds from the known values of the corresponding Sc, Y and La compounds has been developed. The estimated values are believed to be correct within ±20%.