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

The value of $1$ Bohr magneton $(\mu_B)$ is equal to ......... $A \cdot m^2$.

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

Other than $X$-ray diffraction,how can the following pairs of isomers be distinguished from one another?
$[Cr(NH_3)_6][Cr(NO_2)_6]$ and $[Cr(NH_3)_4(NO_2)_2][Cr(NH_3)_2(NO_2)_4]$

Which of the following complexes exhibits both geometrical and optical isomerism?

Which of the following will give the maximum number of isomers?