What is the most abundant gas in Earth's air?
Nitrogen is the most abundant gas in Earth's air, making up about 78 percent of the atmosphere. Oxygen is second at about 21 percent, and argon is third.
Dry air near the ground is about 78 percent nitrogen, 21 percent oxygen and just under 1 percent argon. Everything else together, including carbon dioxide, neon, helium and methane, adds up to only a small fraction. Carbon dioxide, despite its big role in climate, is about 0.04 percent. Air also holds a variable amount of water vapor.
Nitrogen gas is made of two nitrogen atoms held by a very strong triple bond, so it is not very reactive. That is why most living things cannot use it directly from the air. Bacteria in soil and in the roots of plants such as beans and peas convert it into forms plants can absorb.
Why nitrogen matters
Nitrogen is a building block of proteins and DNA. Farmers add nitrogen fertilizers to help crops grow, and the industrial Haber-Bosch process, developed in the early 1900s, made it possible to produce these fertilizers from the nitrogen in the air.
Did You Know?
Liquid nitrogen boils at about −196°C (−321°F). It is used to freeze food quickly, store biological samples and remove warts.