Statement I: Cu⁺, Zn²⁺ ions do not impart any colours to their aqueous solutions

Statement II: In Cu⁺ and Zn²⁺ ions (n −1)d orbitals are completely filled

Statement I and statement II are true and statement II is correct explanation of statement I

The answer is 1. Statement I and statement II are true and statement II is correct explanation of statement I.

Statement I is true because \(Cu^+\) and \(Zn^{2+}\) ions have completely filled (n-1)d orbitals. This means that there are no unpaired electrons in these ions, and unpaired electrons are required for d-d transitions, which are the transitions that cause transition metal compounds to be colored.

Statement II is also true, and it is the correct explanation for statement I. The (n-1)d orbitals are the outermost d orbitals, and they are the ones that are involved in d-d transitions. If these orbitals are completely filled, then there are no unpaired electrons, and no d-d transitions can occur.

Therefore, both statements are true, and statement II is the correct explanation for statement I.