Which gas is the most abundant in air?

By far, the most abundant gas in the Earth’s atmosphere is nitrogen, which accounts for about 78% of the mass of dry air. Oxygen is the next most abundant gas, present at levels of 20 to 21%. Although humid air seems like it contains a lot of water, the maximum amount of water vapor that air can hold is only about 4%. The amount of water vapor is highly variable. In hot, humid locations, it is the third most abundant gas. This makes it the most common greenhouse gas. In dry air, the third most abundant gas is argon, a monatomic noble gas. The abundance of carbon dioxide is variable. While it is an important greenhouse gas, it is only present an average of 0.04 percent, by mass.

It’s important to know which gas is most abundant, what the other gases are in the Earth’s atmosphere, and how the composition of air changes with altitude and over time for multiple reasons. The information helps us understand and predict the weather. The amount of water vapor in the air is particularly relevant to weather forecasting. The gas composition helps us understand the effects of natural and man-made chemicals released into the atmosphere. The make-up of the atmosphere is extremely important for climate, so changes in gases may help us predict broad climate change.

 

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