AIIMS 2012 Chemistry Question Paper for free online practice with solutions

In [Co(NH3)6]3+, oxidation state of Co=+3 and its coordination number is six.
So, 27Co=1s2,2s2,2p6,3s23p63d7,4s2
Co3+=1s2,2s2,2p6,3s23p63d6

Thus, [Co(NH3)6]3+, hows inner orbitalcomplex as well as diamagnetic in behaviour (due to absence of upaired electron).
[Zn(NH3)6]2+→sp3d2 hybridisation (outer) and diamagnetii.
[Cr(NH3)−6]3+→d2sp3 hybridisation (inner) and paramagnetic.