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

Options

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

Answer

A

Explanation

` [Ni(NH_(3))_(6)]^(2+)`
E.C. of ` Ni^(+2) = [Ar]3d^(8) 4s^(0)`

` Ni^(2+)+ "in" [Ni(NH_(3))_(6)]^(2+)`

Shape is octahedral (outer orbital complex).
Due to presence of two unpaired electrons. it is paramagnetic in nature. All the other complexes given are diamangnetic and shave inner orbital complex.