Nitrogen is main ingredient of air. As every twelve-⁠year-⁠old knows, it accounts for 78 percent of the air. Less than 21 percent of air is oxygen. The high percentage of nitrogen in the air is a result of volcanic eruptions during the formation of the Earth. Vast amounts of it were released into the atmosphere. Being heavier than hydrogen or helium it has stayed closer to the surface of the planet. A key ingredient in gunpowder, it is also used to cure meat, as a preservative in ice cream.

The word nitrogen means soda-⁠forming in Greek. Beer cans with pressure-⁠sensitive widgets contain nitrogen, not carbon dioxide. The smaller nitrogen bubbles make a smoother, creamier head. The only other significant gas in air is argon. It was discovered by William John Strutt, who was also the first man to work out why the sky is blue.