The correct order for the wavelength of absorption in the 27. visible region is :

Options

A. `[Ni(NO_(2))_(6)]^(4-) lt [Ni(NH_(3))_(6)]^(2+) lt [Ni(H_(2)O)_(6)]^(2+)`
B. `[Ni(NO_(2))_(6)]^(4-) lt [Ni(H_(2)O)_(6)]^(2+) lt [Ni(NH_(3))_(6)]^(3+)`
C. `[Ni(H_(2)O)_(6)]^(2+) lt [Ni(NH_(3))_(6)]^(2+) lt [Ni(NO_(2))_(6)]^(4-)`
D. `[Ni(NH_(3))_(6)]^(2+) lt [Ni(H_(2)O)_(6)]^(2+) lt [Ni(NO_(2))_(6)]^(4-)`

Answer

A

Explanation

For any metal cation,, the magnitude of `Delta_(0)` depends upon the nature of ligand. Higher the value of `Delta_(0)`, lower will be the wave length absorbed. `Delta_(0)` is crystal field stabilisation energy.
The value of `Delta_(0)` for ligands varies as follows
`H_(2)O lt NH_(3) lt NO_(2)^(-)`
so, the wavelength absorbed will vary in reverse order
`NO_(2)^(-) lt NH_(3) lt H_(2)O`.