Nitrogen

Nitrogen (symbol N, atomic number 7) is a chemical element. In its standard state at room temperature, it exists as a diatomic gas (N2) that is colorless, odorless, and tasteless. Nitrogen is classified as a non-metal.

N2 makes up roughly three-quarters (approximately 78% by volume) of Earth's atmosphere, making it the most abundant gas in the air. The triple bond connecting the two nitrogen atoms is very strong, which means N2 gas is highly stable and does not readily react with other elements.

Chemical properties

Nitrogen has five valence electrons and can therefore form up to three chemical bonds. It can exist in various oxidation states, resulting in diverse compounds such as ammonia (NH3), nitric acid (HNO3), and nitrogen oxides (NO, NO2, N2O). When liquefied, N2 becomes a very cold liquid used in industrial applications (liquid nitrogen).

Life and the nitrogen cycle

Nitrogen is essential to life. It is present in amino acids, proteins, and nucleic acids (DNA and RNA). Most organisms cannot use N2 from the air directly. It must be converted into an accessible form through a process called nitrogen fixation, which is carried out by certain bacteria, some of which live in the root nodules of legumes. Subsequently, other processes such as nitrification and denitrification return nitrogen to the atmosphere as part of the nitrogen cycle.

Industrial use

Nitrogen is used primarily in the production of fertilizer. The Haber-Bosch process combines nitrogen and hydrogen under high pressure and temperature with a catalyst to produce ammonia. Ammonia is the basis for nitrogen-based fertilizers, which significantly increased agricultural yields in recent centuries. Nitrogen gas is also used as an inert atmosphere when working with food preservation, electronics, and metal processing; liquid nitrogen serves as a refrigerant in medicine and research.

Environmental impact

Heavy use of nitrogen fertilizer can lead to nitrate seepage into rivers and groundwater, causing excessive algal growth (eutrophication). Nitrogen oxides from fuel combustion contribute to air pollution and smog formation. Nitrous oxide (N2O) is a greenhouse gas with strong warming potential when compared on a per-unit basis to carbon dioxide.