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The correct order of the number of unpaired electrons in the given complexes is : (A) [Fe(CN)6]3- (B) [FeF6]3- (C) [CoF6]3- (D) [Cr(oxalate)3]3- (E) [Ni(CO)4] Choose the correct answer from the options given below -

1. E < A < D < C < B
2. E < A < B < D < C
3. A < E, C < B < D
4. A < E < D < C < B

Correct answer: E < A < D < C < B

Solution

The correct order reflects the number of unpaired electrons in each complex, which is influenced by factors such as the nature of the ligands and the oxidation states of the metal ions. In this case, CO is a strong field ligand causing pairing of electrons, while CN- and oxalate also promote pairing, while F- is a weak field ligand that does not favor pairing, leading to the specified order.

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