CHEMICAL COMPOSITION OF AIR - Air can contain as much as 5% water vapor, more commonly ranging from 1-3%. The 1-5% range places water vapor as the third most common gas (which alters the other percentages accordingly). Nearly all of the Earth's atmosphere is made up of only five gases: nitrogen, oxygen, water vapor, argon, and carbon dioxide. Several other compounds are also present.

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The Chemical Composition of Air

by Anne Marie Helmenstine, Ph.D. 

Nearly all of the Earth's atmosphere is made up of only five gases: nitrogen, oxygen, water vapor, argon, and carbon dioxide.

Several other compounds are also present.

Although this CRC table does not list water vapor, air can contain as much as 5% water vapor, more commonly ranging from 1-3%.

The 1-5% range places water vapor as the third most common gas (which alters the other percentages accordingly).

Below is the composition of air in percent by volume, at sea level at 15 C and 101325 Pa.

Nitrogen -- N₂ -- 78.084%

Oxygen -- O₂ -- 20.9476%

Argon -- Ar -- 0.934%

Carbon Dioxide -- CO₂ -- 0.0314%

Neon -- Ne -- 0.001818%

Methane -- CH₄ -- 0.0002%

Helium -- He -- 0.000524%

Krypton -- Kr -- 0.000114%

Hydrogen -- H₂ -- 0.00005%

Xenon -- Xe -- 0.0000087%

Ozone -- O₃ -- 0.000007%

Nitrogen Dioxide -- NO₂ -- 0.000002%

Iodine -- I₂ -- 0.000001%

Carbon Monoxide -- CO -- trace

Ammonia -- NH₃ -- trace

Anne Marie Helmenstine, Ph.D.

· Ph.D. in biomedical sciences from the University of Tennessee at Knoxville - Oak Ridge National Laboratory.

· Science educator with experience teaching chemistry, biology, astronomy, and physics at the high school, college, and graduate levels.

· ThoughtCo and About Education chemistry expert since 2001.

· Widely-published graphic artist, responsible for printable periodic tables and other illustrations used in science.

Experience

Anne Helmenstine, Ph.D. has covered chemistry for ThoughtCo and About Education since 2001, and other sciences since 2013. She taught chemistry, biology, astronomy, and physics at the high school, college, and graduate levels. She has worked as a research scientist and also abstracting and indexing diverse scientific literature for the Department of Energy.

In addition to her work as a science writer, Dr. Helmenstine currently serves as a scientific consultant, specializing in problems requiring an interdisciplinary approach. Previously, she worked as a research scientist and college professor. 

Education

Dr. Helmenstine holds a Ph.D. in biomedical sciences from the University of Tennessee at Knoxville and a B.A. in physics and mathematics with a minor in chemistry from Hastings College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive chemical detection and medical diagnostic tests.

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https://www.thoughtco.com/chemical-composition-of-air-604288