•      The air that surrounds us is a mixture of several gases.

Figure 2: Pie-chart of air composition

•      Air is colourless and tasteless and is made up of about 78% nitrogen, 21% oxygen and 1% is composed of small quantities of other gases such as carbon dioxide, ozone, hydrogen, helium etc.

•      It is the Earth’s gravity that holds the layer of air around our planet.



•      Oxygen is a colourless, tasteless, gaseous element which forms 1/5 of the earth's atmosphere.

•      One oxygen molecule is made up of two atoms of oxygen.

•      Oxygen is the most common element found on or in the Earth.

•      It is one of the main elements that make up air, and it is necessary for the survival of all plants and animals.

•      The symbol for oxygen is O.



•      Nitrogen is the most abundant element in our planet’s atmosphere.

•      Approximately 78% of the atmosphere is comprised of nitrogen.

•      Nitrogen is used by life forms to carry out many of the functions .

•      This element is especially important to plant life. Yet nitrogen in its gaseous form is almost entirely unusable to life forms.

•      Nitrogen gas is relatively inert, but  bacteria present in the soil can 'fix' atmospheric nitrogen into a form that plants can use to make amino acids and proteins.

•      Its presence in the air keeps the process of burning under control.

•      Without nitrogen, even small fires would be uncontrollable.


Other gases:

•      1% of the atmosphere is comprised of other gases.

•      Argon is a colourless and odourless gas.

•      It is used in making light bulbs and fluorescent tubes.

•      Water vapour, carbon dioxide, ozone, hydrogen, and helium are some other gases present in air.

•      Carbon dioxide is used by green plants to make their food.



•      Air forms a layer around the Earth. This layer is called the Earth's atmosphere.

•      The first layer of the atmosphere is made up of the gases that we breathe. This layer is called troposphere.

•      The troposphere is the layer that we live in.

•      The next layer of our atmosphere is called the stratosphere. Above the stratosphere lies the mesosphere, followed by the thermosphere, and  the exosphere.


Atmosphere helps us in many ways:

  1. Atmosphere helps in maintaining the right temperature for the survival of living things on the Earth.

•      Clean air is important because, it is what we need to survive.

  1. Ozone which forms a layer in the stratosphere, protects us from the harmful ultraviolet rays of the sun.

•      While ground level ozone is an air pollutant, the ozone layer in the Earth’s upper atmosphere provides protection from the UV rays.

  1. Atmosphere also protects us from meteoroids, which are small rocks moving about in space.

•      Meteoroids may cause harm if they hit the surface of the Earth. Most of these meteoroids burn in the atmosphere before they can reach the surface of the Earth.