The octahedral complex of a metal ion `M^(3+)` with four monodentate ligands `L_(1),L_(2),L_(3)` and `L_(4)` absorb wavelengths in the region of red,green, yellow and bule, respectively The increasing order of ligand strengh of the four ligands is

Options

A. `L_4 lt L_3 lt L_2 lt L_1`
B. `L_1 lt L_3 lt L_2 lt L_4`
C. `L_3 lt L_2 lt L_4 lt L_4`
D. `L_1 lt L_2 lt L_4 lt L_3`

Answer

B

Explanation

For a given metal ion, weak field ligands create a complex with smaller `Delta`, which will absorbs light of longer `lambda` and thus lower frequency . Conservely , stronger field ligands create a larger `Delta, ` absorb light of shorter `lambda` and thus higher v i.e. higher energy.
`underset(lambda= 6.50nm)("Red") lt underset(570 nm)("Yellow") lt underset(490 nm)("Green") lt underset(450 nm)("Blue")`
So order of ligand strength is
`L_1 lt L_3 lt L_2 lt L_4`