Which gas makes up the largest percentage of pure air at sea level?

The gas that makes up the largest percentage of pure air at sea level is nitrogen. Nitrogen constitutes about 78% of the Earth's atmosphere. This is significant because nitrogen plays a critical role in various biological and chemical processes, although it is mostly inert and doesn't directly participate in these processes at typical temperatures and pressures.

Oxygen, while essential for life and comprising about 21% of the atmosphere, is far less abundant than nitrogen. Argon, which accounts for less than 1% of the atmosphere, is primarily a noble gas and does not engage in reactions that support life. Carbon dioxide is also present in trace amounts (approximately 0.04%), but it is crucial for processes like photosynthesis.

Understanding the composition of air, particularly the dominance of nitrogen, is vital in fields such as environmental science, aviation, and meteorology, where knowledge about atmospheric conditions is crucial.