# Question 422af

The average oxidation number of carbon is $+ \frac{4}{3}$.....
For O=""^(+II)C=C^(0)=C^(+II)=O#, the internal carbon, has a FORMAL oxidation number of ${C}^{0}$, the terminal carbons are ${C}^{+ I I}$ (and hence the average value quoted). Element-element bonds are presumed to share electrons rather than exchange them when we assign oxidation states.