Which gas makes up the largest percentage of the Earth's atmosphere?

Nitrogen makes up the largest percentage of the Earth's atmosphere, accounting for about 78% of the atmosphere by volume. This inert gas plays a crucial role in maintaining the balance of gases in the environment, although it is not directly involved in biological processes like respiration. Its abundance is significant in atmospheric science, as it serves as a diluent for oxygen and other gases. Understanding this composition is essential for a variety of fields, including meteorology, aviation, and environmental science.

Oxygen, while vital for human and animal life, constitutes only about 21% of the atmosphere. Carbon dioxide is present in much smaller amounts, approximately 0.04%, and is primarily known for its role in regulating the Earth's temperature and supporting plant life through photosynthesis. Helium is a trace gas found in the atmosphere at even lower levels and is not a major component compared to nitrogen. Therefore, the recognition of nitrogen as the predominant gas is fundamental in understanding atmospheric characteristics.