JEE Main · 2023 · 15 Apr 2023 · Shift 1 · Coordination Compounds

For a fixed ligand and a fixed oxidation state, the crystal field splitting ${\Delta }_o$ grows as the metal-ligand distance shrinks, because the ligands then approach the $d$ orbitals more closely and set up a stronger field. Among the $+3$ hexaaqua ions of titanium, chromium, manganese and iron, the chromium(III) ion has the smallest ionic radius and hence the highest charge density, so the water molecules are drawn in most closely and interact most strongly. The $[\mathrm{Cr}({\mathrm{H}}_2\mathrm{O}{)}_6{]}^{3+}$ ion therefore has the highest magnitude of crystal field splitting energy.