Which of the following is an inner orbital complex as well as diamagnetic in behaviour
[Atomic numbers `Zn` = 30, `Cr` = 24, `Co` = 27, `Ni` = 28.]

Options

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

Answer

C

Explanation

In `[Co(NH_(3))_(6)]^(+)`, oxidation state of Co= + 3 and its coordination number is six.
`""_(27)Co=1s^(2),2s^(2),2p^(6),3s^(2)3p^(6)3d^(7),4s^(2)`
`Co^(3+)=1s^(2),2s^(2)2p^(6),3s^(2)3p^(6)3d^(6)`
`[Co(NH_(3))_(6)]^(+)` is an inner orbital complex as wall as diamagnetic m behaviour (due to absence of unpaired electrons).
`[Zn(NH_(3))_(6)]^(2+)rarr sp^(3) d^(2)` hybridisation (outer orbital complex and diamagnetic in nature.
`[Cr(NH_(3))_(6)]^(3+)rarrd^(2)sp^(3)` hybridisation (inner orbital complex and paramagnetic in nature).