The electron configuration that forms a colorless cation is _____. (transition metals question)?

Question

The electron configuration that forms a colorless cation is _____.
A) 3d6
B) 3d8
C) 3d9
D) 3d10

Answer 1

The answer is D), 3d10. When the d orbital is full, the transition metal ion should be colorless.

Complex formation plays a part in transition metal determining color in a transition compound. This is because of the effect that transition metal elements ligands have on the 3d orbital. Ligands pull on some of the 3d electrons and split them in to higher and lower (in terms of energy) groups. Electromagnetic radiation is only absorbed if its frequency is proportional to the difference in energies between two energy states present in an atom (through the formula e=hf.) When light hits an atom which has had its 3d orbitals split, some of the electrons become promoted to the higher group. Compared to an un-complexed ion, different frequencies can be absorbed, hence different colors are observed.

When 3d orbitals are full - no electrons are able to move up to the higher group, thus it will remain colorless.