Sodium forms only outer-sphere complexes.
The other elements form both outer and inner-sphere complexes, while the most important parameter is the nuclei's ability to hydrolysis. In the case of inner-sphere complexation, it is also possible to determine which hydroxy complex is adsorbed. When log K d is plotted against pH, the slope indicates which complex is formed and adsorbed. The hydrolysis determines whether there is an inner or outer-sphere complexation. The dependence on ionic strength was very low in the case of inner-sphere complexation.