5. Co-ordination chemistry — Chemistry STD 12 Science — Question

The electronic configuration of ${ }_{27} Co =1 s ^2, 2 s ^2, 2 p ^6, 3 s ^2 3 p ^6 3 d ^7, 4 s ^2$

$Co ^{3+}=1 s^2 2 s^2 2 p^6, 3 s^2 3 p^6 3 d^6$

Thus, $\left[ Co \left( NH _3\right)_6\right)^{3+}$ shows inner orbital complex as well as diamagnetic in behaviour (due to absence of an unpaired electron).

$\left[ Zn \left( NH _3\right)_6\right]^{2+} \rightarrow sp ^3 d ^2$ hybridisation (outer) and diamagnetic.

$\left[ Cr \left( NH _3\right)_6\right]^{3+} \rightarrow d ^2 sp ^3$ hybridisation (inner) and paramagnetic.