PREDICTION OF THE MOLECULAR SHAPE OF LANTHANIDE TRIHALIDES

A simple model is offered to interpret and predict the shapes of lanth anide trihalide molecules. According to this model the shape depends m ostly on the asphericity of the 4f electron shell which is buried deep within the 5s5p shell but has relatively large density. The above eff ect, and to a lesser extent the polarizability of the metal ions, dete rmines the molecular shape for the fluorides. For the larger halides t he electronegativity and size of the halogen ligands also influence th e outcome, and the shape is the result of competing effects.