Dinitrogen and dioxygen, the main constituents of air do not react with each other in atmosphere to form oxides of nitrogen because :

The reaction is endothermic and require very high temperature.

N_2 is unreactive in the condition of atmosphere.

Oxides of nitrogen are unstable.

Reaction between them can occur in the presence of a catalyst.

P Block Elements PYQ — JEE Main 2022 · 28 Jul · Shift 2 · Q6 with Solution

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Correct answer: D

We need to explain why the major components of air, $\mathrm{N_2}$ and $\mathrm{O_2}$ , normally do not combine in the atmosphere to form oxides of nitrogen.
Consider the reaction: $\mathrm{N_2 + O_2 \rightarrow 2NO}$ This is the first step in formation of nitrogen oxides.
Important facts about this reaction:

$\mathrm{N_2}$ contains a very strong $\mathrm{N\equiv N}$ triple bond.
Breaking this bond requires a large amount of energy.
Hence, the reaction has a very high activation energy.
The formation of $\mathrm{NO}$ from $\mathrm{N_2}$ and $\mathrm{O_2}$ is endothermic and occurs appreciably only at very high temperatures, such as in lightning or inside automobile engines.

A: $\mathrm{N_2}$ is unreactive in the condition of atmosphere.
This is partly true as a general statement, but it is not the best reason asked here. The more precise reason is that the reaction needs very high temperature due to high bond dissociation energy and endothermic nature.
B: Oxides of nitrogen are unstable.
Incorrect. Several nitrogen oxides such as $\mathrm{NO}$ and $\mathrm{NO_2}$ do exist and are not the reason for non-reaction under atmospheric conditions.
C: Reaction between them can occur in the presence of a catalyst.
This does not answer why they do not react in the atmosphere. Also, the major requirement is high temperature, not simply a catalyst.
D: The reaction is endothermic and require very high temperature.
Correct. This is the standard explanation.