Nitrogen, Oxygen, Carbon Dioxide, Water Vapor and Other Gases: The Varied Components of Air

We all know that life cannot exist without air. The moment they are born, every organism is bound to take and breathe air through their respective functional organs for their survival. Air is considered and proved to be a mixture of gasses by humans. 

The Earth’s atmosphere is made up of four major compounds of gas, which occupy almost 99.998% of the composition of air. These major components are Nitrogen, Oxygen, argon and carbon dioxide.

Another constituent of air is water vapour. Although it occupies the third most abundant gas component of air, it is not mentioned in the composition table. The composition of air without water vapour is also called dry air. Other than those mentioned above, the components present in the air are referred to as trace elements due to their presence in less quantity.

These are the basics of air composition. Now let’s delve deeper.


The following table shows the representations of the atmospheric components with their symbol, molecular weight and percentage ratio by volume.

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%
Others   CO, Xe 0.02%



Nitrogen or ‘N’ occupies 78% of the air we breathe. Nitrogen is the most abundant found gas on the planet though it has its drawbacks. Nitrogen is essential for plants and animal growth and nourishment, but the overabundance of certain nutrients in water can cause several adverse health and ecological effects. 

Nitrogen in the form of nitrate, nitrite or ammonium is a nutrient needed for plant growth.

Nitrogen and its uses;

  • It is used in agriculture to grow crops.
  • It is used in an aircraft fuel system and tire filling system.
  • It is used in stainless steel manufacturing.
  • It is also used in the light bulb industry.

Some of its adverse effects are that it can cause overstimulation of aquatic plants and algae growth. Excessive growth of these organisms, in turn, can clog water intakes, use up dissolved oxygen as they decompose, and block light to deeper waters.

Lake and reservoir eutrophication can occur, which produces unsightly scums of algae on the water surface. It can occasionally result in fish kills and even kill a lake by depriving it of oxygen. The respiration efficiency of fish and aquatic invertebrates can occur, leading to a decrease in animal and plant diversity, affecting our use of the water for fishing, swimming and boating and thus harming the human population directly or indirectly.


Oxygen has its nature of appearance as colourless in gas and pale blue in liquid and solid form. Oxygen is one of the major components of the air around us. Air comprises almost 21% of oxygen. 

Oxygen provides the energy released in combustion and aerobic cellular respiration, and many major classes of organic molecules in living organisms contain oxygen atoms. These include proteins, nucleic acids, carbohydrates and fats, as do the major constituent inorganic compounds of animal shells, teeth, and bone.

Oxygen and its occurrence:

Oxygen is the most abundant chemical element by mass in the earth’s biosphere, air, sea and land. The unusually high concentration of oxygen gas on earth is the result of the oxygen cycle. 

The biogeochemical cycle describes the movement of oxygen within and between its three main reservoirs on earth: the atmosphere, the biosphere and the lithosphere. The main driving factor of the oxygen cycle is photosynthesis, which is responsible for the modern earth’s atmosphere. 

Photosynthesis releases oxygen into the atmosphere, while respiration, decay and combustion remove it from the atmosphere. In the present equilibrium, production and consumption occur at the same rate.                                                                                                                                                                           

Carbon dioxide

There are both natural and human sources of carbon dioxide emissions. Natural sources include decomposition, ocean release and respiration. Human sources come from cement production, deforestation, and the burning of fuel like coal, oil, and natural gas. 

Carbon dioxide is an acidic colourless gas. It occupies 0.033% of the earth’s atmosphere. Its occupancy keeps on changing from one place to another in our atmosphere.

Exposure to carbon dioxide can be hazardous to human health. These may include headaches, dizziness, restlessness, difficulty breathing, sweating, tiredness, increased heart rate, elevated blood pressure, coma, asphyxia, convulsion, etc.

Carbon dioxide is also used as a refrigerant, in fire extinguishers, for inflating life rafts and life jackets, blasting coal, foaming rubber and plastics, promoting the growth of plants in greenhouses, immobilising animals before slaughter, and in carbonated beverages.


Water vapour or aqueous vapour is the gaseous phase of water.  Water vapour is transparent like most other constituents. We know that water present in oceans and rivers evaporates during summer and escapes into the air. Thus water vapour is one of the components of the air.

It occupies a very less percentage of the earth’s atmosphere. It is one state of water within the hydrosphere. Water vapour can be produced from the evaporation or boiling of liquid water or the sublimation of ice. Water vapour is transparent, like most constituents of the atmosphere. Under typical atmospheric conditions, water vapour is continuously generated by evaporation and removed by condensation. It is less dense than most of the other constituents of air and triggers convection currents that can lead to clouds.

Being a component of Earth’s hydrosphere and hydrologic cycle, it is particularly abundant in Earth’s atmosphere, where it acts as a greenhouse gas and warming feedback, contributing more to the total greenhouse effect than non-condensable gases such as carbon dioxide and methane. The use of water vapour, as steam, has been important for cooking and as a major component in energy production and transport systems since the industrial revolution.

Water vapour is a relatively common atmospheric constituent, present in the solar atmosphere and every planet in the Solar System and many astronomical objects, including natural satellites, comets and even large asteroids. 

Water vapour is significant in that it can be indirect evidence supporting the presence of extraterrestrial liquid water in the case of some planetary mass objects. Likewise, the detection of extra solar water vapour would indicate a similar distribution in other planetary systems.


The air you breathe has many components that may surprise you. However, all these play a crucial role in providing us safe and balanced air to breathe and keep us healthy and alive.

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