MHTCET 26 Apr 2025 Shift 2 Paper

Concept:Ligands are arranged by their field strength in the spectrochemical series.Weak field ligands lie at the lower end of this series.Explanation:The spectrochemical series is:$$\mathrm{I}^{-} < \mathrm{Br}^{-} < \mathrm{Cl}^{-} < \mathrm{F}^{-} < \mathrm{OH}^{-} < \mathrm{H}_{2}\mathrm{O} < \mathrm{NH}_{3} < \mathrm{CN}^{-} < \mathrm{CO}$$From the given options, $\mathrm{Br}^{-}$ is a halide ion and appears at the lower end of the series.Thus, $\mathrm{Br}^{-}$ produces the smallest crystal field splitting and acts as a weak field ligand.In contrast, $\mathrm{NH}_{3}$, $\mathrm{NC}^{-}$, and $\mathrm{CO}$ are stronger field ligands.Answer:$\mathrm{Br}^{-}$ is the weak field ligand.