What is Air Made of?

All plants and animals on Earth need oxygen to survive, yet the amount of free oxygen (O2) available in the air and water is very small compared to the total amount of air or water. In particular, only 20.946% of Earth's atmosphere is O2.

(In aquatic environments, the concentration of oxygen is even lower--only between 5 mL/L and 9 mL/L depending on the temperature and salinity. Oxygen dissolves better in colder, fresher water.)

The remainder of Earth's air is nitrogen (N2), water vapor, and trace gases. Below is the list of compounds that make up the atmosphere.

Composition of Air:

Listed from most plentiful to least abundant.

Nitrogen, N2..................... 78.084%
Oxygen, O2...................... 20.946%
Argon, Ar......................... 0.9340%
Water, H2O...................... 0.4% overall, as high as 4% near surface
Carbon Dioxide, CO2.......... 0.039%
Neon, Ne......................... 0.001818%
Helium, He....................... 0.000524%
Methane, CH4................... 0.000179%
Krypton, Kr....................... 0.000114%
Hydrogen, H2.................... 0.000055%
Nitrous Oxide, N2O............ 0.00003%
Carbon Monoxide, CO......... 0.00001%
Xenon, Xe........................ 0.000009%
Nitrogen Dioxide, NO2........ 0.000002%
Iodine, I2......................... 0.000001%
Ozone, O3........................ up to 0.000008%, mostly in the stratosphere
Ammonia, NH3.................. less than 0.000001%

All percentages are by volume, not by weight.



© Had2Know 2010

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