Question

Answer the question on the basis of the passage given below:
Transition metals form a large number of complexes or coordination compounds in which the metal atoms are bound to a number of anions or neutral molecules. The valence bond theory explains the formation, magnetic behaviour, and geometrical shapes, while the crystal field theory explains the effect of different crystal fields on the degeneracy of \(d\)-orbitals energies of the central metal atom/ion. This provides for the quantitative estimation of orbital separation energies, magnetic moments, and spectral and stability parameters. 
Match List - I (Species/ions) with List - II (Colours): 
List - I List - II 

Choose the correct answer from the options given below: 
 

• A. (A)-(III), (B)-(II), (C)-(I), (D)-(IV)
• B. (A)-(IV), (B)-(I), (C)-(III), (D)-(II)
• C. (A)-(II), (B)-(III), (C)-(I), (D)-(IV)
• D. (A)-(III), (B)-(IV), (C)-(II), (D)-(I)

Hint:

The colour of transition metal ions in solution arises from d-d transitions between electron orbitals. The color can vary depending on the metal ion and the nature of the ligands around the metal center. Stronger ligands cause greater splitting of d-orbitals, often resulting in more intense colors.

Answer 1

The Correct Option is C

Let’s analyze the colours of the metal ions:
- (A) \( \text{Mn}^{2+} \): The Mn²⁺ ion in aqueous solutions gives a pink or light pink color due to the transition of electrons in the d-orbitals. This is Option (IV).
- (B) \( \text{Fe}^{3+} \): The Fe³⁺ ion typically appears yellow in solution due to the absorption of certain wavelengths of light that correspond to this colour. This is Option (I).
- (C) \( \text{Ni}^{2+} \): The Ni²⁺ ion gives a green color in aqueous solution due to electron transitions. This is Option (II).
- (D) \( \text{Cu}^{2+} \): The Cu²⁺ ion in aqueous solution is typically blue due to the crystal field splitting. This is Option (III).
Thus, the correct pairing is:
- (A) \( \text{Mn}^{2+} \) - Pink (IV)
- (B) \( \text{Fe}^{3+} \) - Yellow (I)
- (C) \( \text{Ni}^{2+} \) - Green (II)
- (D) \( \text{Cu}^{2+} \) - Blue (III)
Therefore, the correct answer is Option (3).