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

The most abundant gas in Earth's atmosphere is nitrogen, making it a critical component of the air we breathe. Nitrogen constitutes about 78% of the atmosphere by volume, which plays a significant role in various atmospheric processes. Being a relatively inert gas, nitrogen does not easily react with other substances, which helps stabilize the atmosphere and allows life to thrive.

Nitrogen's abundance contributes to the overall composition of the atmosphere, providing a medium in which oxygen and other gases can support life, while also playing a critical role in the nitrogen cycle, essential for nutrient availability in ecosystems. While oxygen is vital for respiration and accounts for approximately 21% of the atmosphere, its proportion is significantly lower than that of nitrogen. Other gases, such as carbon dioxide and hydrogen, are present in much smaller amounts, which is why they cannot be considered the most abundant gases in the atmosphere.