Which gas constitutes the largest percentage of the Earth's atmosphere?

Nitrogen constitutes the largest percentage of the Earth's atmosphere, making up about 78% of it. This gas plays a crucial role in the atmosphere as it is relatively inert and does not readily react with other substances. Its abundance helps to dilute the more reactive gases, such as oxygen and carbon dioxide, thereby stabilizing the atmosphere. Understanding nitrogen's dominance is important for discussions related to atmospheric composition, ecological systems, and the processes of nitrogen fixation that support life on Earth.