High School

Homoleptic octahedral complexes of a metal ion \( M^{3+} \) with three monodentate ligands \( L_1 \), \( L_2 \), and \( L_3 \) absorb wavelengths in the regions of green, blue, and red, respectively.

What is the increasing order of the ligand strength?

1. \( L_1 < L_2 < L_3 \)
2. \( L_2 < L_1 < L_3 \)
3. \( L_3 < L_1 < L_2 \)
4. \( L_3 < L_2 < L_1 \)

Answer :

Final answer:

The increasing order of ligand strength is L3 < L2 < L1. The correct option is 4. L3 < L2 < L1.

Explanation:

The color of coordination complexes is influenced by the specific ligands coordinated to the metal center. Strong-field ligands cause a large split in the energies of d orbitals of the central metal atom, resulting in absorption of higher-energy violet or blue light. Weak-field ligands, on the other hand, cause a smaller split and absorb lower-energy yellow, orange, or red light.

In this specific scenario, L1 absorbs green light, L2 absorbs blue light, and L3 absorbs red light. Since L3 absorbs the highest-energy light, it has the strongest ligand strength, followed by L2, and then L1.