What is the total number of donor atoms present in the Tetracyanonickelate$(II)$ ion?

The coordination number and the oxidation state of the element $E$ in the complex $[E(en)_2(C_2O_4)]NO_2$ (where $en$ is ethylene diamine) are,respectively:

What is the coordination number of $Co$ in $[CoCl_2(NH_3)_4]^+$?

Total number of moles of $AgCl$ precipitated on addition of excess of $AgNO_3$ to one mole each of the following complexes $[Co(NH_3)_4Cl_2]Cl$,$[Ni(H_2O)_6]Cl_2$,$[Pt(NH_3)_2Cl_2]$ and $[Pd(NH_3)_4]Cl_2$ is $...............$ (in $.00$)

$A$ complex compound of $Co^{3+}$ with molecular formula $CoCl_{x} \cdot yNH_3$ gives a total of $3$ ions when dissolved in water. How many $Cl^{-}$ ions satisfy both primary and secondary valencies in this complex?

In the complex ion $[Co(NH_3)_6]^{3+}$,the $NH_3$ molecules are linked to the metal atom by .......