# How do find oxidation numbers with respect to carbon in an unsaturated molecule?

Are you asking how to find the oxidation numbers of $C$ in a molecule of, say, $\text{propane}$?
Well, as for any neutral molecule or salt, the sum of the oxidation numbers is $\text{zero}$. The oxidation number of hydrogen is usually $+ I$ and it is here. Because the electrons in an element-element bond (i.e. in a $C - C$ bond) are conceived to be shared, this gives for propane, ${H}_{3} C \cdot + : C {H}_{2} + \cdot C {H}_{3}$, i.e. oxidation numbers of $2 \times - I I I \text{ + } - I I$. The average oxidation number of $C$ is $- \frac{8}{3}$.