Question

Which of the following cations in their oxidation states forms colored compounds ?

• A. \(\text{Sc}^{3+}\)
• B. \(\text{Ti}^{4+}\)
• C. \(\text{Cu}^+\)
• D. \(\text{V}^{3+}\)

Hint:

Colour needs partly filled d orbitals, as in V3+ (d2).

Answer 1

The Correct Option is D

Step 1: Idea:
Find the ion that is neither $d^0$ nor $d^{10}$.

Step 2: Result:
Sc(III) and Ti(IV) are $d^0$, Cu(I) is $d^{10}$. Only V(III), with $d^2$, has electrons that can move between d levels, so only it gives a coloured compound.

Final Answer:
$\text{V}^{3+}$ forms coloured compounds, option (D). \[ \boxed{\text{V}^{3+}} \]