Nitrogen makes up 78% of the air on Earth.

Nitrogen gas consists of two nitrogen atoms joined by a very strong triple bond. This bond is hard to break, which makes the gas very stable. In 1772, a doctor named Daniel Rutherford first separated nitrogen from other gases. He called it noxious air because animals could not breathe it to stay alive.Oxygen makes up about 21% of the atmosphere. If oxygen levels rose above 25%, forest fires would start much more easily and burn much hotter. The high amount of nitrogen prevents this from happening by acting as a buffer. The rest of the air is made of small amounts of argon, carbon dioxide, and other gases.Living things need nitrogen to build proteins and DNA. Bacteria in the soil turn nitrogen from the air into a form that plants can absorb. This is called nitrogen fixation. In the early 1900s, scientists Fritz Haber and Carl Bosch invented a way to do this artificially to make fertilizer.This process helps grow enough food for billions of people today. Nitrogen also provides most of the weight of our atmosphere. This weight creates the air pressure that keeps our liquid water from boiling away into space.