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

The most abundant gas in the Earth's atmosphere is nitrogen, which makes up about 78% of the atmosphere by volume. Nitrogen is crucial for many biological processes and plays a significant role in the Earth's climate system. It is relatively inert, meaning it does not easily react with other substances, which allows it to remain stable in the atmosphere.

Oxygen, while essential for life and making up about 21% of the atmosphere, is far less abundant than nitrogen. Carbon dioxide, which is a trace gas, currently constitutes about 0.04% (or 400 parts per million) of the atmosphere, playing a key role in climate regulation and photosynthesis, but it is not nearly as prevalent as nitrogen. Argon, another noble gas, is present at approximately 0.93%, making it insignificant in comparison to nitrogen.

This understanding of the composition of the atmosphere is important in fields like environmental science, where the roles of different gases in atmospheric processes can impact climate and weather patterns significantly.