Question

Why nitrogen is more than oxygen and carbon dioxide even tho it is not useful? Why

Answer 1

The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earth's gravity.
By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere.
As you can see, from the time of existence of planet Earth, the composition of its air has remained constant with nitrogen in greater abundance than other gases. However, though we may be more aware of the use of oxygen in our daily lives, Nitrogen too is equally important.
Uses of Nitrogen:
Nitrogen is important to the chemical industry. It is used to make fertilisers, nitric acid, nylon, dyes and explosives
Nitrogen gas is also used to provide an unreactive atmosphere. It is used in this way to preserve foods, and in the electronics industry during the production of transistors and diodes. Large quantities of nitrogen are used in annealing stainless steel and other steel mill products. Annealing is a heat treatment that makes steel easier to work.

Liquid nitrogen is often used as a refrigerant. It is used for storing sperm, eggs and other cells for medical research and reproductive technology. It is also used to rapidly freeze foods, helping them to maintain moisture, colour, flavour and texture.
Biological role
Nitrogen is cycled naturally by living organisms through the ‘nitrogen cycle’. It is taken up by green plants and algae as nitrates, and used to build up the bases needed to construct DNA, RNA and all amino acids. Amino acids are the building blocks of proteins.

Animals obtain their nitrogen by consuming other living things. They digest the proteins and DNA into their constituent bases and amino acids, reforming them for their own use.

Microbes in the soil convert the nitrogen compounds back to nitrates for the plants to re-use. The nitrate supply is also replenished by nitrogen-fixing bacteria that ‘fix’ nitrogen directly from the atmosphere.

Crop yields can be greatly increased by adding chemical fertilisers to the soil, manufactured from ammonia. If used carelessly the fertiliser can leach out of the soil into rivers and lakes, causing algae to grow rapidly. This can block out light preventing photosynthesis. The dissolved oxygen soon gets used up and the river or lake dies.