Which gas is most abundant in the Earth's atmosphere?

Nitrogen is the most abundant gas in the Earth's atmosphere, making up about 78% of the total atmosphere by volume. Its presence is crucial for various biological and chemical processes on Earth. Nitrogen serves as a significant part of the atmosphere because it stabilizes the atmosphere and plays a role in the nitrogen cycle, which is essential for plant growth and the functioning of ecosystems. This high concentration of nitrogen also makes it less reactive compared to other gases, contributing to the overall stability and composition of the atmosphere.

In contrast, gases like oxygen, while vital for respiration and combustion, constitute only about 21% of the atmosphere. Carbon dioxide is much less abundant at around 0.04%, yet it plays a critical role in photosynthesis and the Earth's greenhouse effect, but it is not the most abundant gas. Argon, a noble gas, is present in trace amounts (about 0.93% of the atmosphere). Understanding the composition and abundance of these gases helps to grasp essential concepts regarding Earth's atmosphere and its processes.