N2

N2
Name	Nitrogen
Formula	N2
Molar mass	28.0134 g·mol−1
Appearance	Colorless gas
Density	1.251 g·L−1 (at 273 K)
Melting point	63.15 K
Boiling point	77.36 K
Phase	Gas
Cas number	7727-37-9

N2

N2 is the diatomic molecular form of the chemical element nitrogen, represented by the formula N2, that dominates the composition of Earth's atmosphere and appears in numerous industrial, environmental, and biochemical contexts. It is central to discussions involving Dinitrogen fixation, Haber process, Air separation unit, Cryogenics, and Atmosphere of Earth, and it figures prominently in texts on Chemistry, Physical chemistry, Chemical engineering, Atmospheric chemistry, and Biogeochemical cycles.

Nomenclature and Chemical Properties

The molecular nomenclature for N2 follows conventions set by the International Union of Pure and Applied Chemistry and is treated in systematic treatments alongside diatomic species such as O2, Cl2, H2, F2, and Br2; discussions of bond order and electronic structure reference studies by Linus Pauling, Gilbert N. Lewis, Walther Nernst, Ernest Rutherford, and modern quantum chemists affiliated with institutions like Massachusetts Institute of Technology, California Institute of Technology, and Max Planck Society. Its chemical properties—triple covalent bonding, high bond dissociation energy, and nonpolarity—are analyzed in contexts including the Molecular orbital theory expositions by Robert Mulliken and computational work from groups at Harvard University, Stanford University, and ETH Zurich. Standard nomenclature, CAS registry entries, and InChI keys align with documentation from IUPAC, International Organization for Standardization, and major chemical suppliers such as Air Products and Chemicals and Linde plc.

Occurrence and Production

N2 constitutes about 78% of the Atmosphere of Earth by volume, a fact central to studies by explorers and scientists from James Hutton-era geoscience to modern analyses by NASA, European Space Agency, NOAA, National Aeronautics and Space Administration, and observatories such as Mauna Loa Observatory. Geological reservoirs of nitrogen occur in the crust and mantle, considered in research from United States Geological Survey, British Geological Survey, Geological Society of London, and field campaigns led by oceanographers and geochemists at Scripps Institution of Oceanography and Woods Hole Oceanographic Institution. Industrial production relies on cryogenic distillation pioneered by companies like Air Liquide, BASF, and Air Products and Chemicals, as well as pressure swing adsorption technologies developed at Siemens and in academic labs at Imperial College London and University of Cambridge.

Physical and Thermodynamic Properties

Physical and thermodynamic properties of N2—such as triple-bond energy, heat capacity, enthalpy of formation, entropy, and compressibility—are tabulated in compilations by NIST, CRC Handbook of Chemistry and Physics, and standard texts by Irvine Langmuir, Linus Pauling, G. N. Lewis, and resources used at Massachusetts Institute of Technology and University of California, Berkeley. The liquid and solid phases are central to cryogenic engineering and facility designs at CERN, Fermilab, and European Organization for Nuclear Research installations, and behavior under high pressure figures in research by Diamond Light Source and High Pressure Research Group investigators.

Reactivity and Chemical Uses

N2 is relatively inert under ambient conditions due to its strong triple bond; transformation into reactive species underlies the Haber process for ammonia synthesis developed by Fritz Haber and Carl Bosch and the Birch reduction-type chemistry. Reactive conversion pathways are studied by catalysis groups at Max Planck Institute for Chemical Energy Conversion, ETH Zurich, Caltech, and Stanford University, and applied in processes linked to Fertilizer production companies such as Yara International and CF Industries. N2 participates in high-energy reactions in rocket propulsion (studied by SpaceX, NASA, Roscosmos), plasma processes researched at Lawrence Berkeley National Laboratory, and nitration or nitriding protocols in metallurgical settings at ArcelorMittal and academic metallurgy groups.

Industrial and Laboratory Applications

Industrial uses of N2 include inerting and blanketing in operations at ExxonMobil, Shell plc, Bayer, and Dow Chemical, cryogenic preservation in medical facilities like Mayo Clinic and Johns Hopkins Hospital, and use as a carrier gas in analytical instruments produced by Agilent Technologies, Thermo Fisher Scientific, and Shimadzu Corporation. Laboratory applications span glovebox atmospheres employed in research at University of Oxford and University of Cambridge, sample storage in biobanks such as those coordinated by Wellcome Trust, and welding atmospheres used by manufacturers including Boeing and Airbus.

Environmental and Biological Roles

Biologically, fixed forms of nitrogen produced from N2 via biological nitrogen fixation by organisms like Rhizobium, Azotobacter, and symbioses studied with Carl Woese and groups at Rockefeller University enter ecosystems and agriculture, influencing work by FAO and CGIAR institutes. Atmospheric chemistry involving N2 interrelates with NOx formation, ozone chemistry investigated by Paul Crutzen and Mario Molina, and climate considerations addressed by IPCC, United Nations Environment Programme, and observatories including NOAA. Geological cycling of nitrogen is examined in tectonics research pursued at Scripps Institution of Oceanography and Lamont–Doherty Earth Observatory; medical and physiological studies of inert gas effects reference research from Harvard Medical School and Johns Hopkins University.

Category:Nitrogen compounds