The atmosphere is a mechanical mixture of several gases. It also contains a number of solid and liquid particles called‘Aerosols’. Some of the gases may be permanent. They remain in fixed proportion but others may vary in quantity from one place to another and from time to time. The different constituents of the atmosphere are gases, water vapor and dust particles.

Gases: The dry air that is around us is a mixture of various gases. The main component gases of dry air are listed in the table. Both nitrogen and oxygen together account for about 99% of the atmosphere. The remaining 1% to make up of other gases. Nitrogen is most plentiful of all the gases in the atmosphere. It is an important constituent of many organic compounds. It is needed to dilute the air and regulated combustion by diluting oxygen. All living organism need oxygen. For respiration. Life is not possible without it. It is essential for combustion. About 21% of the gases in the atmosphere consist of oxygen. 

Carbon dioxide is found in small percentage in dry air. It used by green plants for photosynthesis. It absorbs solar energy and earth radiation and then emits a part of it towards the earth. The amount of carbon dioxide is increasing every year which can agent temperature. Another important gas is ozone, which is similar to oxygen molecule. It absorbs most of the ultra-violet rays from the sun and protects us from excessive heat.

Water vapour: This is the gaseous form of water. It is largely formed from the evaporation of water from the water bodies on the earth and transpiration from plants and soils.

Water vapor is one of the most variable gases of the atmosphere, which is representing in the lower layers of the atmosphere. It is capable of absorbing solar energy as the well as energy radiated form the earth. The condensation of water vapour is responsible for several forms of the precipitation. Eg: rain, snow, etc. The amount of water vapor mainly depends on temperature. So it. varies from place to place and from time to time. It decreases from the equator to the poles.

Dust particles: The atmosphere is capable of holding solid particles, suspended in the lower layers of the atmosphere. They consist of dust, salt particles, pollen, smoke and soot, volcanic ash etc. These dust particles are very important form the absorption and scattering of some of the solar energy.

Water vapor is one of the most variable gases of the atmosphere, which is representing in the lower layers of the atmosphere. It is capable of absorbing solar energy as the well as energy radiated form the earth. The condensation of water vapour is responsible for several forms of the precipitation. Eg: rain, snow, etc. The amount of water vapor mainly depends on temperature. So it.varies from place to place and from time to time. It decreases from the equator to the poles.

Dust particles: The atmosphere is capable of holding solid particles, suspended in the lower layers of the atmosphere. They consist of dust, salt particles, pollen, smoke and soot, volcanic ash etc. These dust particles are very important form the absorption and scattering of some of the solar energy.