(a) The [Ni(OH₂)₆]²⁺ ion is green, whereas [Ni(NH₃)₆]²⁺ ion is purple and [Ni(en)₃]²⁺ is violet. Which complex ion absorbs light with the shorter wavelength? explain.

(b) The isoelectronic ions VO₄ ^3- (colorless), CrO₄^2- (yellow), and MnO₄ (purple) all have intense charge transfer transitions. The wavelengths of these transitions increase in this series with MnO₄ having its charge transfer absorption at the longest wavelength. Suggest a reason for this trend.

(c) Coordination compounds undergoes two main mechanisms. Does the complex [CoCl(NH3)5]Cl2 prefer SN1 mechanism or SN2 mechanism. Give reasons for your choice and write equations to explain the mechanism.