Which gas is most abundant in Earth's atmosphere?

Nitrogen is the most abundant gas in Earth's atmosphere, comprising approximately 78% of the total composition. This significant percentage reflects its essential role in the atmosphere and its involvement in various biological and chemical processes. Nitrogen is inert under standard conditions, which helps to maintain atmospheric stability. While oxygen, carbon dioxide, and argon are present in smaller quantities—oxygen makes up about 21%, carbon dioxide is around 0.04%, and argon is nearly 0.93%—they do not match the dominance of nitrogen in terms of overall volume. Understanding the atmospheric composition is crucial because it has implications for climate science, respiratory health, and environmental studies.