Diagram illustrating relative abundances of gases in Earth's atmosphere

Credit: Randy Russell, UCAR SciEd

This diagram shows the relative abundances of the main gases in Earth's atmosphere. Nitrogen makes up 78%, oxygen about 21% and argon almost 1%. Lesser constituents include carbon dioxide at 400 parts per million (0.04%) and everything else (neon, helium, methane, krypton, hydrogen, etc.) at less than 28 parts per million combined.