Final answer:
The oxidation number of the nitrogen atom in N₂O₃ is +4.
Step-by-step explanation:
The oxidation number of a nitrogen atom in N₂O₃ can be determined by assigning oxidation numbers to the other atoms in the compound and using the rules of oxidation numbers. In N₂O₃, oxygen is normally assigned an oxidation number of -2 and there are three oxygen atoms. The nitrogen atom is bonded to two oxygen atoms, so we can set up the equation: x + 2(-2) = 0, where x is the oxidation number of nitrogen. Evaluating for x, we find that the oxidation number of the nitrogen atom in N₂O₃ is +4.