Question
A solution of [Ni (H2O)6]2+ is green but a solution of [Ni(CN)4]2– is colourless. Explain.
Solution
Ni(CN)42– has no unpaired electron in its d sub shell and thus d - d transition is not possible whereas Ni(H2O)62+ has compaired electron in its d-subshell which give rise to d - d transition to impart colour.