Air. The Earth’s atmosphere is basically a product of the organisms living in it. Here is the approximate composition of the earth’s atmosphere: 78.09 % (by volume) nitrogen, 20.95 % (by volume) oxygen, varying amounts of water vapor (0.002—4% by weight), 0.93 % (by volume) argon, 0.038 % (by volume) carbon dioxide and a small amount of hydrogen, helium, other gases and pollutants. Surface air always contains a large amount of suspended solid and liquid particles forming aerosols. Above 120 km distribution of chemicals under the influence of gravity becomes significant. That is why closer to the surface molecular and atomic oxygen and nitrogen dominate, and above — hydrogen and helium, which due to the low atomic weight slowly dissipate into space.