Arrange the following complexes in order of increasing crystal field splitting .
`[Fe(H_(2)O)_(6)]^(2+),[Fe(H_(2)O)_(6)]^(3+) , [FeCl_(6)]^(4-)` .

Explanation

To arrange the complexes `[Fe(H₂O)₆]²⁺`, `[Fe(H₂O)₆]³⁺`, and `[FeCl₆]⁴⁻` in order of increasing crystal field splitting, we need to consider the following factors:

1. **Nature of the Ligands**: The ligands in these complexes influence the extent of crystal field splitting. Water (H₂O) is a weak field ligand, while chloride (Cl⁻) is an even weaker field ligand. Therefore, the complex with chloride will have the smallest crystal field splitting.

2. **Oxidation State of the Metal Ion**: The oxidation state of the metal ion also affects the crystal field splitting. A higher oxidation state leads to a greater positive charge, which increases the attraction between the metal ion and the ligands, resulting in larger splitting.

Now, let's analyze the given complexes:

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