Dinitrogen (N2) and dioxygen (O2) are the main constituents of air but they do not react with each other to form oxides of nitrogen because

Dinitrogen (N2) and dioxygen (O2) are the primary components of the atmosphere, yet they do not react under normal conditions due to the extreme stability of the nitrogen molecule. Nitrogen atoms are held together by a very strong triple bond. Breaking this bond to initiate a reaction with oxygen requires a significant amount of energy, making the formation of nitric oxide (NO) a highly endothermic process. Consequently, the reaction has a very high activation energy and only proceeds at extremely high temperatures, such as those exceeding 3000 K found in thermal plasmas, lightning strikes, or internal combustion engines [1]. At ambient temperatures, the energy available is insufficient to overcome this barrier, preventing the spontaneous formation of nitrogen oxides in the air. Therefore, the reaction is limited by its endothermic nature and the requirement for high thermal energy.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > 4.1 BONDING IN CARBON – THE COVALENT BOND > p. 60