The number of possible optical isomers for $[Co(en)_2 Cl_2]^+$ is ....

What is the value of the spin-only magnetic moment for $Cu^{2+}$ in $BM$?

There are four complexes of $Ni$. Select the complex(es) which will be attracted by a magnetic field:
$(I) \ [Ni(CN)_4]^{2-}, \ (II) \ [NiCl_4]^{2-}, \ (III) \ [Ni(CO)_4]$
$(IV) \ [Ni(H_2O)_6]^{2+}$

The two compounds $[Co(SO_4)(NH_3)_5]Br$ and $[Co(SO_4)(NH_3)_5]Cl$ represent:

Among the following complexes,the one that can exhibit optical activity is

The value of the 'spin only' magnetic moment for one of the following configurations is $2.84 \ BM$. The correct one is: