What is the primary gas in the Earth's atmosphere?

The primary gas in the Earth's atmosphere is nitrogen (N2), which makes up about 78% of the atmosphere by volume. Nitrogen is an inert gas, meaning it does not readily react with other substances under normal conditions, and it plays a crucial role in various biological processes. While oxygen is essential for life and constitutes about 21% of the atmosphere, nitrogen's abundance makes it the predominant component contributing to the overall composition. Carbon dioxide and argon are present in much smaller amounts, with carbon dioxide being crucial for plant photosynthesis and argon being a noble gas that has minimal chemical activity. Understanding the proportions of these gases helps explain various atmospheric processes, including the role of nitrogen in maintaining atmospheric stability and balance.