Which gas constitutes the majority of air by volume?

Nitrogen makes up a significant portion of the atmosphere, constituting about 78% of the air by volume. This inert gas is crucial for various geological and biological processes, providing stability in the atmosphere and playing a minor role in direct biological interactions. It is a non-reactive gas under most conditions, which contributes to its prevalence in the air.

While oxygen is essential for life and accounts for approximately 21% of the atmosphere, it is not the majority component. Carbon dioxide and argon represent even smaller fractions of the atmospheric composition, with carbon dioxide being around 0.04% and argon about 0.93%. Therefore, in terms of majority composition by volume, nitrogen holds the clear distinction as the dominant gas in the air we breathe.