Oxides Of Nitrogen

Nitrogen forms several oxides with different oxidation states and acid-base characters. Nitrous oxide, N_2O, in which nitrogen has an average oxidation state of +1, is a neutral oxide because it does not react with water to give an acid or a base and does not form salts. It is the gas commonly called laughing gas and is used as a mild anaesthetic and analgesic in dentistry and surgery. Nitric oxide, NO, is also neutral but is not the anaesthetic in question and is a colourless reactive gas. Nitrogen dioxide, NO_2, is an acidic, brown, toxic gas that forms acids with water. Dinitrogen pentoxide, N_2O_5, is the acidic anhydride of nitric acid. Identifying the nature and uses of nitrogen oxides is a standard NCERT topic. Plausibility check: the well-known anaesthetic use and neutral, non-salt-forming behaviour both point specifically to nitrous oxide, confirming the answer.