Question

Which from following elements forms coloured compound in its respective oxidation state?

• A. Sc\(^{3+}\)
• B. Ti\(^{4+}\)
• C. Zn\(^{2+}\)
• D. Cr\(^{3+}\)

Hint:

Transition metal ions with unpaired electrons in their d-orbitals typically form coloured compounds due to d-d electron transitions.

Answer 1

The Correct Option is D

Step 1: Recall the general property of transition metal ions.
Transition metal ions often form coloured compounds due to d-d electron transitions. When an electron in a lower energy level absorbs energy, it moves to a higher energy level, causing the compound to appear coloured.

Step 2: Analyze Sc\(^{3+}\), Ti\(^{4+}\), Zn\(^{2+}\), and Cr\(^{3+}\).
- Sc\(^{3+}\) has no d-electrons, so it does not show any colour.
- Ti\(^{4+}\) has a d\(^0\) configuration, so it also does not show any colour.
- Zn\(^{2+}\) has a d\(^10\) configuration, and therefore does not undergo d-d transitions, resulting in no colour.
- Cr\(^{3+}\) has a d\(^3\) configuration, which allows for d-d transitions, and thus it forms a coloured compound.

Step 3: Identify the correct element.
Out of the given options, Cr\(^{3+}\) forms a coloured compound.

Step 4: Final answer.
\[ \boxed{\text{Cr}^{3+}} \] which matches option \((4)\).