Oxygen Oxidation Number

[Olivia Young 1A]

Is the oxidation number of oxygen always -2? My teacher in high school told me that, but I am not sure if that is always true because difference molecules can affect the oxidation number of oxygen differently.

[Isabelle Fontanilla 1I]

O2 will have an oxidation number of 0 because it is in its elemental form.
Oxygen will have a -1 ON when it is found in peroxides (e.g. H202).
Everything else will yield a -2 ON for Oxygen.

[whitney_2C]

Oxygen is usually assigned an oxidation state of ‒2 in its covalent compounds, such as CO, CO2, SO2, and SO3. Exceptions to this rule include peroxides (compounds containing the O2-2 group), where each oxygen is assigned an oxidation state of ‒1, as in hydrogen peroxide (H2O2), and OF2 in which oxygen is assigned a +2 oxidation state. You can check to see the oxidation states of oxygen by drawing out the Lewis Structure and calculating formal charge.

[Carlos De La Torre 2L]

Oxygen will tend to have a -2 charge due to the face that it wants an octet and due to its high electronegativity it will usually have the octet at the cost of having a formal charge of -2