nitrogen

nitrogen
Name	nitrogen
Category	nonmetal
Group	15
Appearance	colorless gas, liquid or solid
Atomic weight	14.007
Electron configuration	1s² 2s² 2p³
Phase at STP	gas
Melting point K	63.15
Boiling point K	77.36
Density gpcm3n	0.0012506
Triple point K	63.151
Critical point K	126.21
Discovered by	Daniel Rutherford
Discovery date	1772
Named by	Jean-Antoine Chaptal
Named date	1790

nitrogen. It is a colorless, odorless, and mostly inert diatomic gas under standard conditions, constituting the bulk of Earth's atmosphere. First isolated by the Scottish physician Daniel Rutherford in 1772, it was later named by the French chemist Jean-Antoine Chaptal. This element is fundamental to all life, being a key component of amino acids, proteins, and nucleic acids like DNA.

Properties

At room temperature, it exists as the highly stable N₂ molecule, held together by a strong triple bond that requires significant energy to break. This element exhibits several allotropes, with atomic nitrogen being highly reactive. It is less dense than air and has a low boiling point of -195.8°C, making it useful in cryogenic applications. The liquid form is a clear fluid often employed as a refrigerant. In its solid state, it forms a crystalline structure. The spectral lines of atomic nitrogen are prominent in the aurora and certain stellar atmospheres. Its electronegativity is high, ranking behind only fluorine and oxygen on the Pauling scale.

Occurrence and production

It is the most abundant uncombined element in Earth's atmosphere, making up about 78% by volume. Significant deposits of nitrate minerals, such as Chile saltpeter, are found in arid regions like the Atacama Desert. It is also a component of all living organisms, found in biomass worldwide. Industrially, it is primarily produced on a massive scale via the fractional distillation of liquid air in facilities like those operated by Linde plc or Air Products. Smaller quantities are generated by passing air over heated copper or through membrane technology. In nature, lightning and certain soil bacteria convert atmospheric N₂ into more usable forms through nitrogen fixation.

Compounds

Despite the inertness of N₂, it forms an immense variety of compounds, often involving high-energy processes. The most economically significant is ammonia, produced via the Haber process and used globally in fertilizers. Nitric acid is a vital industrial chemical used in explosives like TNT and fertilizer production. Oxides include nitrous oxide, used in anesthesia, and nitrogen dioxide, a component of smog. Cyanide compounds contain carbon-nitrogen bonds and are used in mining and organic synthesis. Amino acids like glycine are the building blocks of proteins, while nucleobases such as adenine are essential for RNA and DNA. Many high-energy materials, including ammonium nitrate and RDX, are nitrogen-based.

Biological role

It is an essential element for all known life forms. It is a fundamental constituent of amino acids, which polymerize to form proteins and enzymes that catalyze biochemical reactions. Nucleic acids like DNA and RNA, which carry genetic information, contain nitrogenous bases. The nitrogen cycle describes its movement between the atmosphere, soil, and living organisms, involving processes like nitrogen fixation performed by bacteria in the root nodules of legumes like soybeans. Nitrification and denitrification are carried out by microorganisms such as Nitrosomonas and Pseudomonas. A deficiency can limit plant growth, which is why fertilizers from the Haber process are critical to global agriculture, supporting crops from the American Midwest to the Indo-Gangetic Plain.

Applications

Its largest use is in the production of ammonia for fertilizers, underpinning modern agriculture as developed by Fritz Haber and Carl Bosch. The liquid form is a crucial cryogen for preserving biological samples, freezing food, and in superconductivity research at facilities like CERN. As an inert gas, it is used for blanketing explosive chemicals, in the electronics industry for semiconductor manufacturing, and in packaging snacks like potato chips to prevent rancidity. The oil and gas industry uses it for well stimulation and pipeline purging. Compounds like nitrous oxide are used in rocket propellants and as an oxidizer in internal combustion engines at events like the Indianapolis 500.

Safety and precautions

While the gaseous form is non-toxic, it can act as a simple asphyxiant by displacing oxygen in confined spaces, a hazard in industries from shipbuilding to wine production. Rapid release of large volumes in enclosed areas can lead to oxygen deficiency and unconsciousness without warning. Contact with liquid nitrogen causes severe cryogenic burns and frostbite. Vessels containing it can explode due to pressure build-up if not fitted with proper pressure relief devices. Some of its compounds, such as hydrogen cyanide and nitrogen dioxide, are highly toxic and were infamously used in Zyklon B and are monitored by agencies like the Occupational Safety and Health Administration. Decompression sickness, known as "the bends," involves nitrogen bubbles forming in the bloodstream of divers ascending too quickly.

Category:Chemical elements Category:Pnictogens Category:Atmospheric chemistry