Using IUPAC norms write the formula for the following:
Potassium tetracyanonickelate(II)

How many geometrical isomers are possible in the following coordination entity?

$\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_3{\mathrm{Cl}}_3\right]$

Draw the structures of optical isomers of ${\left[{\mathrm{PtCl}}_2{\left(\mathrm{en}\right)}_2\right]}^{2+}$.