Which gas makes up the largest percentage of air by volume?

Nitrogen comprises the largest percentage of air by volume, making up about 78%. It is an inert gas, which means it does not readily react with other substances under standard conditions, and thus plays a critical role in maintaining the stability of the atmospheric composition.

Oxygen is essential for combustion and respiration, accounting for about 21% of the atmosphere, while argon, a noble gas, makes up approximately 0.93%. Carbon dioxide, though very important for processes such as photosynthesis, only constitutes about 0.04% of the atmosphere. This understanding of the relative percentages of these gases highlights why nitrogen is the predominant component of the air we breathe.