Tue. Aug 2nd, 2022
    Liquid nitrogen

    Nitrogen is the chemical element with atomic number 7, symbol N (from Latin nitrogenium)

    Nitrogen is the head of the group of pnictogens. In everyday language, nitrogen designates the simple body N2 (dinitrogen), the major constituent of the earth’s atmosphere, representing almost 4 / 5ths of air (78.06%, by volume). Nitrogen is the 34th element in the earth’s crust in order of importance.

    The minerals containing nitrogen are mainly nitrates, in particular potassium nitrate KNO3 (constituent of saltpeter) or nitre, which was once used to make explosive powders, and sodium nitrate  NaNO3 (constituent of saltpeter from Chile).

    Nitrogen has many industrial uses. It is particularly widely used as a fertilizer in industrial agriculture (in the form of ammonium compounds), to the point where it is today its main use in the world, a use responsible for generalized pollution of the environment.

    An element that looks like a Swiss army knife

    Possessing a complex life cycle, nitrogen can be found in many forms and has different uses.

    – In ammonia and nitrate, it is used as fertilizer for agriculture.
    – Found in potassium nitrate, it also serves as a food preservative.
    – In its liquid form, it is used as a refrigerant for biological samples or in molecular cooking.
    – It can also be found in the tires of airliners or racing cars since it helps limit tire pressure losses.

    Nitrogen has a wide range of uses but can also have negative consequences on health and the environment.

    The risks associated with nitrogen

    Found in nitrate, nitrogen is used as a fertilizer. Ingesting too much nitrate can have health consequences by reducing oxygen supply to cells, but it is especially for the environment that excessive use of nitrate is dangerous.

    Indeed, the excess nitrate not absorbed by plants is dispersed by rains in seawater, rivers and groundwater and causes water pollution. Bacteria and toxic algae then develop and disrupt ecosystems. This is called the phenomenon of eutrophication.

    In the longer term, it is considered that nitrogen could also lead to acidification of natural environments and therefore soils, and thus have negative consequences on agriculture.

    Finally, when it encounters other pollutants in the air, nitrogen becomes a greenhouse gas and thus contributes to global warming.

    Nitrogen oxide, a harmful derivative

    Nitrogen oxide is a gas which can be hazardous to health. Thus, when nitrogen meets oxygen, or when a nitrogenous product oxidizes, emissions of this dangerous gas can occur at high temperatures.

    This is the case, for example, when burning gasoline in a car. As such, road transport was responsible in 2012 for 54% of nitrogen oxide emissions. It is, moreover, the leading transmitter in mainland France.

    Among its negative effects, nitrogen oxide can be irritating to the bronchi and cause breathing difficulties or pulmonary edema – especially in asthmatics or other frail people.

    Applications / uses

    Examples of uses of the molecule in industry and health

    Is used for heat treatment, welding or for laser cutting. Tires inflated with nitrogen have an extended life.

    Is used for heat treatment, welding or for laser cutting. It is also used in the production of auto parts by gas assisted injection molding process. Tires inflated with nitrogen have an extended life.

    Is used directly in chemical processes as a carrier gas or fluidization agent, or for temperature control and the preparation of catalysts. It is also involved in several processes at petrochemical sites: inerting, drying, purging, mixing, etc.

    Electronic components
    Nitrogen allows the inerting of the atmosphere in order to avoid any oxidation phenomenon during the wave or reflow soldering process. Nitrogen is used as a carrier gas for protection against impurities and oxidation during semiconductor production and welding. It provides an inert atmosphere suitable for the waiting phases during the production of material and for the wafer containers during their transport. Nitrogen allows the dilution of reactive by-products rejected during the manufacture of semiconductors, until the safety threshold is reached. Nitrogen is used to cool the wafers without contamination after treatment.

    It is used for cooling, freezing or controlling the temperature of foodstuffs. It allows temperature control during transport and distribution thanks to the indirect injection of liquid nitrogen. Nitrogen preserves and protects foodstuffs through Protective Atmosphere Packaging (MAP) by minimizing oxidation, microorganism development and packaging crushing. It is also used for the protection of liquid foods against oxidation through inerting, pressure transfer and deoxygenation.

    When mixed with hydrogen, it creates a reducing atmosphere above the tin bath during glass production.

    Hospital health
    Medical device: it is used for cryo-dermatology and cryo-preservation. It is also a component of the gas mixture used during functional respiratory tests.

    Laboratories and Research Center
    It is a carrier gas for gas chromatography in the context of various analyzes and quality control in industrial and hospital environments. It is also a balance gas for the calibration of gas mixtures intended for the control of gaseous emissions and of working environment sensors. Nitrogen is used for purging, drying or inerting analyzers or chemical reactors (in gaseous or liquid form at low temperature).

    Metal fabrication
    It is used for heat treatment and laser cutting.

    Metal foundry
    It is used for inerting and mixing in many processes.

    Oil & Gas
    For storage tanks and pipes, it protects products and installations (inerting). It is also used in cleaning / pigging operations, pipe purging, cleaning and leak detection. For unbalanced boreholes, nitrogen is used for gas lift and fracturing.

    It is used in the heat treatment for various metals. It is a component of mixtures used in carbon dioxide lasers. It is also used for the pneumatic transport of flammable powdery materials (charcoal).

    Pharma & Biotechnology
    It is used for inerting, cryo-grinding, lyophilization, drying, liquid phase transfer of products or synthetic intermediates. It is also used for the cryo-condensation of gaseous effluents and for storage at low temperature.

    Nitrogen in the periodic table

    Atomic number (Z)7
    Groupgroup 15 (pnictogens)
    Periodperiod 2
    Block  p-block
    Electron configuration[He] 2s2 2p3
    Electrons per shell2, 5

    Physical properties

    Physical properties
    Phase at STPgas
    Melting point(N2) 63.23 K ​(−209.86 °C, ​−345.75 °F)
    Boiling point(N2) 77.355 K ​(−195.795 °C, ​−320.431 °F)
    Density (at STP)1.2506 g/L at 0 °C, 1013 mbar
    when liquid (at b.p.)0.808 g/cm3
    Triple point63.151 K, ​12.52 kPa
    Critical point126.21 K, 3.39 MPa
    Heat of fusion(N2) 0.72 kJ/mol
    Heat of vaporisation(N2) 5.57 kJ/mol
    Molar heat capacity(N2) 29.124 J/(mol·K)

    Vapour pressure

    P (Pa)1101001 k10 k100 k
    at T (K)374146536277

    Atomic properties

    Atomic properties
    Oxidation states−3, −2, −1, +1, +2, +3, +4, +5 (a strongly acidic oxide)
    ElectronegativityPauling scale: 3.04
    Ionisation energies
    • 1st: 1402.3 kJ/mol
    • 2nd: 2856 kJ/mol
    • 3rd: 4578.1 kJ/mol
    • (more)
    Covalent radius71±1 pm
    Van der Waals radius155 pm

    Other properties

    Other properties
    Natural occurrenceprimordial
    Crystal structure​hexagonal
    Speed of sound353 m/s (gas, at 27 °C)
    Thermal conductivity25.83×10−3 W/(m·K)
    Magnetic orderingdiamagnetic
    CAS Number17778-88-0
    7727-37-9 (N2)


    Nomenclature and origin
    Antoine Lavoisier chose the name nitrogen, composed of a- (private) and the Greek radical ζωτ- (“living”) and which therefore means “deprived of life”, because unlike oxygen it does not maintain the animal life 6.

    DiscoveryDaniel Rutherford (1772)
    Named byJean-Antoine Chaptal (1790)

    The origin of the symbol N is its Latin name nitrogenium which comes from the Greek nitron gennan, which means “saltpeter” (potassium nitrate). The English term nitrogen has retained this root to designate nitrogen, while the French term “nitrogen” is no longer used today.

    Main isotopes of nitrogen

    Nitrogen (N) has 16 known isotopes of mass number varying from 10 to 25, as well as a nuclear isomer, 11mN. Two of them are stable and present in nature, 14N and 15N, the first representing almost all of the nitrogen present (99.64%). They are widely used for isotopic studies, in particular of the nitrogen cycle1 and food webs.

    Main isotopes of nitrogen
    Iso­topeAbun­danceHalf-life (t1/2)Decay modePro­duct
    13Nsyn9.965 minε13C

    Periodic Table of Elements | Complete List of Chemical Elements by Group, Name, Symbol, Color and Type

    Periodic table elements
    Periodic Table of Elements | Complete List of Chemical Elements by Group, Name, Symbol, Color and Type

    Sources: PinterPandai, Nitrogen Foot Print

    Photo credit: Cory Doctorow / Flickr

    Phoro explanation: Liquid Nitrogen, PicoCon, Imperial College, London.