Question

Identify the factor responsible for colour of transition metal compounds.

• A. d-d transitions
• B. s-p mixing
• C. Ionisation
• D. Shielding effect

Hint:

Partly filled d orbitals split in a ligand field and absorb visible light for d-d jumps.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
In a compound of a transition metal ion, the five d orbitals split into two energy groups because of surrounding ligands.

Step 2: Detailed Explanation:
An electron can jump from a lower d level to a higher d level by absorbing a photon of visible light. This is a d-d transition. The colour we see is the complement of the colour absorbed.
This needs partly filled d orbitals. Ions with \(d^0\) or \(d^{10}\) configurations, such as \(\text{Sc}^{3+}\) and \(\text{Zn}^{2+}\), are colourless.
s-p mixing, ionisation and shielding effect do not produce absorption in the visible range.

Step 3: Final Answer:
d-d transitions, option (A).

Final Answer:
d-d transitions absorb visible light. \[ \boxed{\text{(A) }d\text{-}d\ \text{transitions}} \]