Question

Which from following metal ions in their respective oxidation states forms colourless compounds?

• A. \(\text{Ti}^{4+}\)
• B. \(\text{V}^{3+}\)
• C. \(\text{Cu}^{2+}\)
• D. \(\text{Mn}^{2+}\)

Hint:

Rule: \(d^0\) or \(d^{10}\) → colourless compounds.

Answer 1

The Correct Option is A

Concept:
Colour in transition metal ions arises due to d–d transitions. If no electrons are present in d-orbitals (\(d^0\) or \(d^{10}\)), compounds are colourless.

Step 1: Check electronic configuration.
• Ti$^{4+}$ → \(3d^0\) → no d-electrons → colourless \checkmark
• V$^{3+}$ → \(3d^2\) → coloured $\times$
• Cu$^{2+}$ → \(3d^9\) → coloured $\times$
• Mn$^{2+}$ → \(3d^5\) → weakly coloured $\times$ Conclusion: \[ \text{Colourless ion = Ti}^{4+} \]