Atmospheric air comprises certain elements in a specific ratio. According to NASA (National Aeronautics and Space Administration), 99.998 percent of the Earth's atmosphere is made up of four compounds. These major components are nitrogen, oxygen, argon and carbon dioxide. Another major component of the Earth's atmosphere is water vapor, which is not included in studying the dry composition of air. In short, air composition without water vapor is called dry air. The percentage of water vapor may range from 1-5 percent. Substances present in the air, other than these five main components are referred to as trace elements. Read more on planet earth facts.
Composition of Air
The composition of air in the atmosphere remains nearly unchanged till an altitude of 10 meter. Dust particles also make up the atmospheric air to some extent. Any major alteration in the percentage composition of air is associated with changes in the global climate. The following table represents the components of atmospheric air with their symbol, molecular weight and percentage ratio by volume:
Table for Composition of Air
| Component | Element Symbol | Molecular Weight | Percent by Volume |
| Nitrogen | N2 | 28.01 | 78.084% |
| Oxygen | O2 | 32.00 | 20.947% |
| Argon | Ar | 39.95 | 0.934% |
| Carbon Dioxide | CO2 | 44.01 | 0.033% |
| Neon | Ne | 20.18 | 0.001818% |
| Helium | He | 4.00 | 0.000524% |
| Krypton | Kr | 83.80 | 0.000114% |
| Methane | CH4 | 16.04246 | 0.0002% |
| Hydrogen | H2 | 2.02 | 0.00005% |
| Nitrous Oxide | N2O | 44.01288 | 0.00003% |
| Xenon | Xe | 131.30 | 0.0000087% |
| Ozone | O3 | 47.9982 | 0.000007% |
| Nitrogen dioxide | NO2 | 46.005 | 0.000002% |
| Iodine | I2 | 253.8 | 0.000001% |
| Carbon monoxide | CO | 28.0101 | Trace |
| Ammonia | NH3 | 17.03 | Trace |
For easy understanding of air composition at the first glance, you can also refer to a pie chart for the composition of air which you will find plentiful on-line. The major role played by each of these components is different. For example, nitrogen is the most important plant nutrient, while oxygen is responsible for respiration and combustion. Nitrogen is also important for diluting the oxygen concentration and stabilizing the atmosphere.
Air Components: Quick Facts
Concentrations of greenhouse gases in the air is important for studying the global climatic change. The raising level of greenhouse gases like carbon dioxide and methane in the atmosphere is the major cause for global warming. It is because of the increasing greenhouse gases that raises the concern of melting of glaciers and elevation in the global temperature.
The level of aerosols (smoke, smog, pollutants, etc.) suspended in the air is a determining factor for the Earth's energy budget. Atmospheric aerosols change the heat retention by the Earth's surface and also, cloud formation. Overall, aerosols are another factor for changing the energy budget of the Earth. Studies are going on to determine the effects of aerosols in regional and global climatic changes.
The water vapor holding capacity of air varies with temperature. The higher the temperature of air, the lesser is the content of water vapor. This is the reason why, water vapor concentration differs from one place to another. Air in areas near to the sea contain higher concentration of water vapor, while air in desert environments contain low levels of moisture.
While studying respiration, generally we come across statements like breathing in oxygen and releasing carbon dioxide. It is not exactly the case; the air that we breathe out (exhaled air) is not entirely carbon dioxide. A maximum percentage of it makes up moisture, 4.4 percent carbon dioxide, 14 percent oxygen and other elements.
With the rising issues of environmental issues or most precisely, air pollution, studying the composition of air has become a topic of common interest. Scientific studies opine that concentration of oxygen less than 19.5 percent in the atmosphere can result in various physiological changes in all the life forms. And an atmospheric condition with oxygen amount below 16 percent is life threatening.