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There aren't any 'air' molecules, but you already knew this, right? Nearly all of the Earth's atmosphere is made up of only five gases: nitrogen, oxygen, water vapor, argon, and carbon dioxide. Several other additional elements and compounds are 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). This is 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

Reference: CRC Handbook of Chemistry and Physics, edited by David R. Lide, 1997.

Comments

February 17, 2010 at 11:52 pm
(1) Steven says:

…What about Water vapor? I suppose its variable.. but what is the average?

December 11, 2012 at 12:18 pm
(2) rose says:

this is way to hard to read make it evenmore easy for kids to read

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