Magnetic moment is expressed in

Among $(i) [Co(NH_3)_6]Cl_3$,$(ii) [Ni(NH_3)_6]Cl_2$,$(iii) [Cr(H_2O)_6]Cl_3$,$(iv) [Fe(H_2O)_6]Cl_2$,the complex which is diamagnetic is $....$

Total number of unpaired electrons present in the central metal atoms/ions of $[Ni(CO)_{4}]$,$[NiCl_{4}]^{2-}$,$[PtCl_{2}(NH_{3})_{2}]$,$[Ni(CN)_{4}]^{2-}$ and $[Pt(CN)_{4}]^{2-}$ is . . . . . . .

Assertion : $[Co(NO_2)_3(NH_3)_3]$ does not show optical isomerism.
Reason : It has a plane of symmetry.

What is the reason for the deviation between the experimental and theoretical values of magnetic moment?

The compound which does not show paramagnetism is