Nitrogen is a chemical element with the atomic number 7 and symbol N. It is a colorless, mostly odorless diatomic non-metal gas. It is also found in soil and water as nitrites and nitrates. These molecules are related to one another and are all a component of the nitrogen cycle. As a result of reactions in the nitrogen cycle, industrial enterprises generate large amounts of nitrogen, which raises the levels of nitrite and nitrate in the ground and water. It is used to make nitric acid, which is then converted into ammonia and used as fertilizer. For freezing and refrigerating operations, liquid nitrogen is used as a refrigerant. Liquid nitrogen is also used for the stable storage of biological materials, as well as the preservation of bodies and reproductive cells.