Question

Explain: the compounds of copper (II) are colored but those of zinc are colorless?

Answer 1

You have a `d^9` electronic configuration in the case of `Cu(+II)`..

Explanation:

...and you gots a `d^10` electronic configuration in the case of `Zn(+II)`.. `Cu(+II)` has a `d^9` electronic configuration, and the colours exhibited by transition metal complexes are in part due to `d-d` transitions (i.e. the energy difference in orbital configuration corresponds to the visible region). These electronic transitions are not available to the `Zn(+II)` complex, whose `"d-orbitals"` are completely filled.