The air is primarily composed of five gases: nitrogen, oxygen, argon, carbon dioxide and water vapor. In addition to these five gases, there are also trace amounts of several gases, but these make up much less than one percent of air.
The composition of air is necessary for life on Earth. It is mostly made of nitrogen, around 78 percent by volume. The second most abundant element is oxygen, required for respiratory processes, which makes up about 21 percent of the atmosphere's air. The final one percent is most argon, but there are also significant amounts of both carbon dioxide and water vapor.