The number of optical isomers possible for $[Cr(C_{2}O_{4})_{3}]^{3-}$ is $.....$ .

The correct statement on the isomerism associated with the following complex ions,
$A$. $[Ni(H_2O)_5NH_3]^{2+}$
$B$. $[Ni(H_2O)_4(NH_3)_2]^{2+}$ and
$C$. $[Ni(H_2O)_3(NH_3)_3]^{2+}$ is

The complex which has facial $(fac)$ and meridional $(mer)$ isomers is
(Given: $py = \text{pyridine}$ and $en = H_2N-CH_2-CH_2-NH_2$)

$A$ compound of a metal ion $M^{x+}$ $(Z = 24)$ has a spin-only magnetic moment of $\sqrt{15} \ BM$. The number of unpaired electrons in the compound is:

Which one of the following complex ions has geometrical isomers?

The number of paramagnetic metal complex species among $[Co(NH_3)_6]^{3+}$,$[Co(C_2O_4)_3]^{3-}$,$[MnCl_6]^{3-}$,$[Mn(CN)_6]^{3-}$,$[CoF_6]^{3-}$,$[Fe(CN)_6]^{3-}$ and $[FeF_6]^{3-}$ with the same number of unpaired electrons is $............$