# What is the oxidation number of oxygen in CO2?

The oxidation state of carbon in carbon dioxide is $I {V}^{+}$.
Oxygen takes its standard oxidation state of $- I I$; $C$ therefore takes its maximum oxidation state. What are the oxidation states of $C$ in elemental $C$, $C O$, and carbon suboxide, ${C}_{3} {O}_{2}$?