Final answer:
The oxidation state of oxygen in NO2 is -2, which can be determined by knowing that nitrogen has an oxidation state of +4 in NO2 and the molecule is neutral.
Step-by-step explanation:
The oxidation state of O in NO2 can be determined by considering the oxidation state of nitrogen and the overall charge of the molecule.
Typically, oxygen has an oxidation state of -2.
Since the nitrogen in NO2 has an oxidation number of +4, and the molecule is electrically neutral, we can set up the following equation: x + 2(-2) = 0, where x is the oxidation number of nitrogen, which is +4.
Solving this equation, we find that each of the two oxygen atoms has an oxidation state of -2.