Nitrogen: dilutes the effect of oxygen and controls the rate of combustion. Needed for proteins and important compounds like fertilizers, ammonia, and nitric acid. Used to keep food fresh because it does not allow the growth of oxygen by preventing oxidation.
Oxygen: needed to sustain life, and for combustion
Carbon dioxide: needed for photosynthesis, retains heat in the atmosphere, and balances temperature on earth. Used in fire extinguishers.
Inert gases: Helium is used in meteorological balloons, Neon is used in light bulbs, and Radon is used in the treatment of cancer. Krypton and Xenon are used in photography.
Dust particles and water vapors help in the formation of clouds.