The oxidation number of $\text{Cr}$ in ${\mathrm{CrO}}_5$ is_______.

Structure of ${\mathrm{CrO}}_5$

Oxidation Number of $\text{Cr}$ in ${\mathrm{CrO}}_5$

• The oxidation number of $\text{Cr}$ be x.
• Four oxygen atoms are attached to Cr through a single bond. The oxygen is in peroxide form. Hence oxidation state of the oxygen atom, in this case, is $-1$.
• Another oxygen atom is attached through a double bond and this has an oxidation number $-2$.

$$\begin{gathered} x+\left(-2\right)+4\left(-1\right)=0 \\ x=+6 \end{gathered}$$

Hence, the oxidation number of $\text{Cr}$ in ${\mathrm{CrO}}_5$ is $+6$.