Which one of the following is an outer orbital complex and exhibits paramagnetic behaviour ?

Options

A. `[Co(NH_3)_6]^(3+)`
B. `[Cr(NH_3)_6]^(3+)`
C. `[Ni(NH_3)_6]^(2+)`
D. `[Zn(NH_(3))_(6)]^(2+)`

Answer

C

Explanation

In `[Zn(NH_3)_6]^(3+)`, `Zn` exists as `Zn^(2+)`
`._30Zn: 3d^(10)`, `4s^2`
`Zn^(2+): 3d^(10)`, Thus, no unpaired electron but it is outer orbital complex.
In `[Co(NH_3)_6]^(3+)`, Co exists as `Co^(3+)`
`._(27)Co: 3d^7`, `4s^2`
`Co^(3+): 3d^(6)`, It is `d^2sp^3` inner orbital complex with 3 electron paired in `3d`.