Question

What will be the correct order for the wavelengths of absorption in the visible region for the following : 

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

Answer 1

The order of the ligand in the spectrochemical series is H₂O < NH₃ < NO₂^-. 

Hence the wavelength of the light observed will be in the order :

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

Thus, the wavelength of light absorbed (E = \(\frac{hc}{\lambda}\) ) will be in the opposite order :

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