Redox Reactions

$\quad \mathrm{Hg}_2(\mathrm{I}) \mathrm{Cl}_2$ is reduced form of $\mathrm{Hg}(\mathrm{II}) \mathrm{Cl}_2$

$\quad \mathrm{Hg}(\mathrm{II}) \mathrm{Cl}_2$ is oxidised form of $\mathrm{Hg}_2(\mathrm{I}) \mathrm{Cl}_2$

It helps to identify whether species is present in oxidised form or reduced form

Aurous chloride is written as Au (III) $\mathrm{Cl}_3$