The degree of complex formations decreases in the order:
An+4 > AnO2+2 > An+3 > AnO2+
Why the order is like this? Please explain in detail.
The actinides have a greater tendency to form complexes than lanthanides because their ions have high charge and are smaller ions. In other words, there is a high concentration of charge on the metal atom and within the given order the latest is decreasing from An+4 to AnO2+.