Composition of Air

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Composition of Air

The composition of the atmosphere air comprises four major gases, namely nitrogen, oxygen, argon, and carbon dioxide. Other substances are present in a very small amount, and hence, they are collectively known as trace components. Read this article to get more information about this subject.

Fast Fact

Scientific studies opine that if oxygen concentration is less than 19.5 percent in the atmosphere, various physiological changes can take place in all the life forms on Earth. An atmospheric condition with oxygen amount below 16 percent is life-threatening to all the organisms.

Atmospheric air consists of 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 constituent 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. The components present in the air, other than the above-mentioned five main ones are referred to as trace elements, as their quantity is small.

The atmospheric air composition remains nearly unchanged till an altitude of 10 meter. Dust particles also make up this composition up to some extent. Any major alteration in the percentage of different elements is associated with changes in the global climate. The following table represents the atmospheric components 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 the elemental composition, you can also refer to a pie chart for the same, and such examples are easily available on the Internet. 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. The former is also important for diluting the latter’s concentration, and for 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 such gases like carbon dioxide and methane is the major cause for global warming. This 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, as well as by the cloud formations. 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 air temperature, 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 close to the sea consist of higher concentration of water vapor, while air in desert environment contain low levels of moisture.

While studying respiration, 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 is moisture, and 4.4% of it is carbon dioxide, 14% oxygen, and other elements.

With the rising concern of environmental issues like air pollution, studying the air composition has become a topic of common interest. Scientific studies opine that if oxygen concentration is less than 19.5 percent in the atmosphere, various physiological changes in all the life forms could be resulted. And an atmospheric condition with oxygen amount below 16 percent is life-threatening.

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