Which one of the following is an inner orbital complex as well as diamagnetic in nature?

Options

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

Answer

B

Explanation

In ` [Co (NH_(3))_(6)]^(3+)` , 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)`
`""^(27 ) Co ^(3+) = 1S ^(2) 2S ^(2) 2p^(6) 3S ^(2) 3p ^(6) 3d^(6) `

it is an inner orbital complex as well as diamagnetic in behaviour while `[Zn(NH_(3))_(6) ]^(2+)to Sp^(3) d^(2)` (outer ) and
diamagnetic and ` [Cr (NH_(3) )_(6) ]^(3+) to d^(2) sp^(3) ` ( inner ) and paramagnetic .