Introduction:
Cations are atoms that have lost electrons and have a positive charge. Transition metals and alkali/alkaline earth metals have different electronic configurations for their cations.

Polarisation:
Polarisation is the ability of an ion to distort the electron cloud of an anion. This occurs when the cation attracts the electrons of the anion towards itself. The degree of polarisation depends on the size and charge of the cation.

Electronic Configuration:
Transition metals have an electronic configuration of (n-1)d"ns". This means that they have electrons in their d orbitals, which are closer to the nucleus and have more effective nuclear charge. This makes the transition metal cations more polarising as they have a greater ability to attract electrons towards themselves.

Alkali and alkaline earth metals have a noble gas configuration of "ng" "np". This means that they have a completely filled valence shell and do not have any electrons in their d orbitals. This makes their cations less polarising as they do not have the ability to attract electrons towards themselves as strongly as transition metals.

Example:
For example, consider the cations Cu2+ and Mg2+. Both have a 2+ charge and are of similar size. Cu2+ has an electronic configuration of [Ar]3d9, while Mg2+ has a noble gas configuration of [Ne]. Cu2+ has electrons in its d orbitals, which are closer to the nucleus and have more effective nuclear charge. This makes Cu2+ more polarising than Mg2+.

Conclusion:
In conclusion, transition metal cations are more polarising than alkali and alkaline earth metal cations due to their electronic configuration. The presence of electrons in the d orbitals of transition metals makes them more effective at attracting electrons towards themselves, compared to alkali and alkaline earth metals with a noble gas configuration.