Which of the following statements is incorrect?

Options

A. In ferrocyanide ion, the effective atomic number is 36
B. Ferricyanide ion is more stable than ferrocyanide ion
C. `[Cr(H_(2)O)_(6)]^(3+) and [Cr(NH_(3))_(6)]^(3+)" have "sp^(3)d^(2) and d^(2)sp^(3)` and have and hybridization respectively.
D. In `[Co(H_(2)O)_(6)]^(2+)` the hybridization `sp^(3)d^(2)` is while in `[Co(NH_(3))_(6)]^(3+)` the hybridization is `d^(2)sp^(3)`

Answer

C

Explanation

For `[Fe(CN)_(6)]^(4-)` effective atomic number= atomic number –oxidation state `+2 xx6` (electrons from ligands) =26-2+12=36. Hence statement (1) is correct
In ferricyanide ion Fe is in +3 oxidation state while in ferrocyanide ion Fe is in +2 oxidation state. complexes are more stable than `Fe^(2+)` complex due to higher value of CFSE. Hence statement (2) is correct. statement (3) is incorrect, in `Cr^(3+)` the electronic configuration is `[M]3d^(6)` Already inner d-orbitals are present. Hence, whether with strong field or weak field ligands, inner d-orbitals can be provided for bonding. Hence hybridization is `d^(2)sp^(3)`. The electronic configuration `Co^(3+)" of is "[M]3d^(6)`
Hence inner d-orbitals are not available. So, with strong field ligands inner d complexes are formed but with weak field ligands outer d complexes are formed. Hence, (1), (2) and (4) statements are correct while statement (3) is incorrect