Nitrogen can exhibit +1 to +5 oxidation state due to its half-filled orbital.
N in NO has a formal oxidation number of +II. Since oxygen is slightly more electronegative than nitrogen, oxygen formally gets the electrons, to give N2+ and O2−
Nitrogen oxide also called nitric oxide is a colourless gas produced by the reaction of metals with dilute nitric acid which then reacts with O2 in the air to form the brown NO2 gas.
