Homoleptic octahedral complexes of a metal ion ′ M 3 + ′ with three monodentate ligands L 1 , L 2 a n d L 3 absorb wavelengths in the region of green, blue and red respectively. The increasing order of the ligand strength is:

Step-by-step solution

Observed order of wavelengths, λ a b s = L 3 > L 1 > L 2 . (Red light has highest wavelength of 700 nm while blue is the shortest with a wavelength of about 480 nm) So, ∆ 0 (strength of ligands) order will be L 2 > L 1 > L 3 . (As ∆ 0  α  1 λ a b s ) Hence, order will be L 2 > L 1 > L 3 . Therefore, Strength of ligand ∝ ∆ A b s o r p t i o n .