Question

Based on Crystal Field theory, match the Complex ions listed in Column I with the electronic configuration in the d orbitals of the central metal ion listed in Column II.

• A. [Mn(CN)_6]^{4-} (P) e_g^2 t_{2g}^3
• B. [Co(H_2O)_6]^{2+} (Q) t_{2g}^6 e_g^0
• C. [Fe(H_2O)_6]^{2+} (R) t_{2g}^6 e_g^2
• D. [MnCl_4]^{2-} (S) e_g^3 t_{2g}^4

Hint:

When dealing with complex ions and their electronic configurations, the strength of the ligand (weak or strong field ligands) plays a major role in determining the arrangement of electrons in the \(t_{2g}\) and \(e_g\) orbitals.

Answer 1

The Correct Option is A

- [Mn(CN)_6]^{4-} (A) has a \(d^5\) configuration, which corresponds to \(e_g^2 t_{2g}^3\) due to the strong field ligand CN⁻ causing pairing of electrons in the lower \(t_{2g}\) orbital. This matches with configuration (R). - [Co(H_2O)_6]^{2+} (B) has a \(d^7\) configuration, leading to a weak field interaction with water molecules as ligands, resulting in configuration (S), which is \(e_g^3 t_{2g}^4\). - [Fe(H_2O)_6]^{2+} (C) has a \(d^6\) configuration, which leads to a relatively weaker splitting of the orbitals, with electrons occupying \(t_{2g}^6 e_g^0\). This corresponds to configuration (P). - [MnCl_4]^{2-} (D) has a \(d^5\) configuration, which corresponds to (Q) \(t_{2g}^6 e_g^0\), consistent with a low-spin case.