MHTCET 18 Apr 2026 Shift 1 Paper

Concept:The spectrochemical series ranks ligands according to their field strength, which is their ability to split the degenerate $d$-orbitals of a central metal ion.Explanation:According to the spectrochemical series, the given ligands appear in the following order:$$\mathrm{S}^{2-} < \mathrm{H}_{2}\mathrm{O} < \mathrm{NCS}^{-} < \mathrm{NH}_{3}$$This order represents the increasing magnitude of crystal field splitting energy ($\Delta_{o}$) produced by each ligand.A ligand positioned further to the right in this series causes a greater splitting of the metal $d$-orbitals.Consequently, $\mathrm{S}^{2-}$ acts as a weak-field ligand, while $\mathrm{NH}_{3}$ lies at the extreme right among the given options.Hence, $\mathrm{NH}_{3}$ produces the largest $d$-orbital splitting and therefore exhibits the highest field strength.The other ligands, $\mathrm{H}_{2}\mathrm{O}$, $\mathrm{NCS}^{-}$, and $\mathrm{S}^{2-}$, all lie to the left of $\mathrm{NH}_{3}$ in the series.Answer:Therefore, the correct answer is option B: $\mathrm{NH}_{3}$.