The number of unpaired electrons associated with Ni in the complex ${\left[\mathrm{Ni}{\left({\mathrm{NH}}_3\right)}_6\right]}^{2+}$ is

The number of unpaired electrons associated with Ni in the complex ${\left[\mathrm{Ni}{\left({\mathrm{NH}}_3\right)}_6\right]}^{2+}$ is two.

The chemical compound with the formula $\left[\mathrm{Ni}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_2$ is known as hexaamminenickel chloride. It is the ${\left[\mathrm{Ni}{\left({\mathrm{NH}}_3\right)}_6\right]}^{2+}$ metal ammine complex's chloride salt. Six ammonia ligands, or ammines in coordination chemistry, are joined to the nickel (II) ion to form the cation.

Hence, option B is correct.