Chemical element, symbol N and atomic number 7 / From Wikipedia, the free encyclopedia

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Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bond to form N2, a colorless and odorless diatomic gas. N2 forms about 78% of Earth's atmosphere, making it the most abundant uncombined element in air. Because of the volatility of nitrogen compounds, nitrogen is relatively rare in the solid parts of the Earth.

Quick facts: Nitrogen, Allotropes, Appearance, Standard at...
Nitrogen, 7N
A transparent liquid, with visible evaporation, being poured
Liquid nitrogen (N2 at below 196 °C)
Allotropessee § Allotropes
Appearancecolorless gas, liquid or solid
Standard atomic weight Ar°(N)
  • [14.00643, 14.00728]
  • 14.007±0.001 (abridged)[1]
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
Phase at STPgas
Melting point(N2) 63.23[2] K (−209.86[2] °C, −345.75[2] °F)
Boiling point(N2) 77.355 K (−195.795 °C, −320.431 °F)
Density (at STP)1.2506 g/L[3] 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) 1 10 100 1 k 10 k 100 k
at T (K) 37 41 46 53 62 77
Atomic properties
Oxidation states−3, −2, −1, 0,[4] +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
Color lines in a spectral range
Spectral lines of nitrogen
Other properties
Natural occurrenceprimordial
Crystal structure hexagonal
Hexagonal crystal structure for nitrogen
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)
DiscoveryDaniel Rutherford (1772)
Named byJean-Antoine Chaptal (1790)
Isotopes of nitrogen
Main isotopes Decay
abun­dance half-life (t1/2) mode pro­duct
13N trace 9.965 min β+ 13C
14N 99.6% stable
15N 0.4% stable
Symbol_category_class.svg Category: Nitrogen
| references

It was discovered and isolated by Scottish physician Daniel Rutherford in 1772, (first publication). Carl Wilhelm Scheele and Henry Cavendish independently did so at about the same time. The name nitrogène was suggested by French chemist Jean-Antoine-Claude Chaptal in 1790 when it was found that nitrogen was present in nitric acid and nitrates. Antoine Lavoisier suggested instead the name azote, from the Ancient Greek: ἀζωτικός "no life", as it is an asphyxiant gas; this name is used in a number of languages, and appears in the English names of some nitrogen compounds such as hydrazine, azides and azo compounds.

Elemental nitrogen is usually produced from air by pressure swing adsorption technology. About 2/3 of commercially produced elemental nitrogen is used as an inert (oxygen-free) gas for commercial uses such as food packaging, and much of the rest is used as liquid nitrogen in cryogenic applications. Many industrially important compounds, such as ammonia, nitric acid, organic nitrates (propellants and explosives), and cyanides, contain nitrogen. The extremely strong triple bond in elemental nitrogen (N≡N), the second strongest bond in any diatomic molecule after carbon monoxide (CO),[5] dominates nitrogen chemistry. This causes difficulty for both organisms and industry in converting N2 into useful compounds, but at the same time it means that burning, exploding, or decomposing nitrogen compounds to form nitrogen gas releases large amounts of often useful energy. Synthetically produced ammonia and nitrates are key industrial fertilisers, and fertiliser nitrates are key pollutants in the eutrophication of water systems. Apart from its use in fertilisers and energy stores, nitrogen is a constituent of organic compounds as diverse as Kevlar used in high-strength fabric and cyanoacrylate used in superglue.

Nitrogen occurs in all organisms, primarily in amino acids (and thus proteins), in the nucleic acids (DNA and RNA) and in the energy transfer molecule adenosine triphosphate. The human body contains about 3% nitrogen by mass, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes the movement of the element from the air, into the biosphere and organic compounds, then back into the atmosphere. Nitrogen is a constituent of every major pharmacological drug class, including antibiotics. Many drugs are mimics or prodrugs of natural nitrogen-containing signal molecules: for example, the organic nitrates nitroglycerin and nitroprusside control blood pressure by metabolizing into nitric oxide. Many notable nitrogen-containing drugs, such as the natural caffeine and morphine or the synthetic amphetamines, act on receptors of animal neurotransmitters.