What will be the correct order for the wavelength of absorption in the visible region for the following: [Ni(NO2)6]4-, [Ni(NH3)6]2+, [Ni(H2O)6]2+

In all the complex the central metal atom/ion is nickel, Ni. Hence the absorption of wavelength from visible region depends on the ligands attached. The order in which the CFSE energy values of ligands increase according to the spectrochemical series is as follows:


So the order of crystal field splitting of d orbitals will also be in the same order because more will be the CFSE energy more will be the energy gap between orbitals. Hence order of wavelength absorption

[Ni(NO2)6]4- <[Ni(NH3)6]2+ < [Ni(H2O)6]2+