Question

Which of the following elements in +3 oxidation state forms colourless compounds?

• A. \(\text{Sc}\)
• B. \(\text{Ni}\)
• C. \(\text{Cr}\)
• D. \(\text{V}\)

Hint:

Colour comes from d-d transitions, which need partly filled d orbitals; Sc3+ has d0.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
Coloured compounds arise from d-d electron transitions. These need at least one d electron and at least one empty d orbital.

Step 2: Detailed Explanation
\(\text{Sc}^{3+}\): \([\text{Ar}]\) \(3d^0\), no d electrons, so it is colourless.
\(\text{Ni}^{3+}\): \(3d^7\), \(\text{Cr}^{3+}\): \(3d^3\), \(\text{V}^{3+}\): \(3d^2\). All have partly filled d orbitals, so they are coloured.

Final Answer:
Sc in +3 state gives colourless compounds, option (A). \[ \boxed{\text{Sc}} \]