Explain `[Co(NH_3)_6]^(3+)` is an inner orbital complex whereas `[Ni(NH_3)_6]^(2+)` is an outer orbital complex.

Explanation

In the complex `[Co(NH_(3))_(6)]^(3+)`, the oxidation state of cobalt is `+3` and has `3d^(6)` configuration. In the presence of `NH_(3)` molecules (ligands), two 3d electrons pair up and two 3d orbitals remain empty. Since sex ligands are to be accommodated the hybridisation of the metal ion is `d^(2)sp^(3)`.

As inner d-electrons are involved, the complex is inner orbital complex and is diamagnetic in nature.
In the complex `[Ni(NH_(3))_(6)]^(3+)` , the oxidatioin state of Ni is `+2` and has `3d^(8)` configuration. Since six `NH_(3)` molecules (ligands) are to be accomodated, the hybridisation of metal ion is `sp^(3)d^(2)`. This means that 4d orbitals are involved in the hybridisation.

the complex is paramagnetic as well as outer oribital complex since outer (4d) electrons are involved in the hybridisation.