The octahedral complex of a metal ion M3+ with four monodentate ligands L1, L2, L3 and L4 absorb wavelengths in the region of red, green, yellow and blue, respectively. The increasing order of ligand strength of the four ligands is : (a) L L L L (b) L L L L (c) L L L L (d) L L L L

The relation between the energy of the ligand and wavelength is given as hc = λ . This means that the energy is inversely proportional to the wavelength blue green yellow red λ <λ <λ <λ Hence, the strength of the ligand will be 1 3 2 4 L <L <L <L Hence, the correct answer is option (a)