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.

It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772 and independently by Carl Wilhelm Scheele and Henry Cavendish 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), 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.

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Atomic properties

Standard atomic weight14.007 ±0.001 [14.0064 … 14.0072]
Atomic mass14.0067 u

Atomic radii

Radius (empirical)65 pm
Radius (calculated)56 pm
Covalent radius71 ±1 pm
Van der Waals radius155 pm

Atomic shell

Electron configurationHe 2s2 2p3
Ionization energy(1st) 14.53413 eV
(2nd) 29.60125 eV
(3rd) 47.4453 eV
(4th) 77.4735 eV
(5th) 97.8901 eV
Shell model

Physical properties

Density0.00125 g·cm−3 (273.1 K)
Molar volume1.354·10-5 m3·mol−1
Speed of sound333.6 m·s−1 (298.1 K)


Melting point63.23 K
Boiling point77.35 K
Liquid range14.12 K
Triple point63.15 K @ 12.52 kPa
Critical point126.2 K @ 3.39 MPa


Melting enthalpy0.36 kJ·mol-1
Enthalpy of vaporization2.79 kJ·mol-1
Binding energy473 kJ·mol-1

Heat and conductivity

Specific heat capacity1,040 J·kg−1·K−1 (298 K)
Thermal conductivity0.02583 W·m-1·K-1



Optical properties

Refractive indexgaseous: 1
liquid: 1.197

Chemical properties

Basicitystrongly acidic
Oxidation state-3, -2, -1, 0, 1, 2, 3, 4, 5


Pauling scale3.04
Sanderson scale3.19
Allred-Rochow scale3.07
Mulliken scale2.9
Allen scale3.066
Ghosh-Gupta scale7.496 eV
Boyd-Edgecombe scale3.08
Nagle scale3.12
Pearson absolute negativity7.3 eV

Other properties

Natural occurrenceprimordial
Crystal structureHexagonal
Goldschmidt Classificationatmophile
Superconductorwith transition tempperature under special conditions
Price/kg0.14 USD

Natural abundances

1·106 ppb ≈ 1·1016 M☉
1·106 ppb ≈ 1.98·1015 Mt
1.4·106 ppb ≈ 1.4 kg
Earth’s crust
20,000 ppb ≈ 554,000 Mt
500 ppb ≈ 685 Gt
Flowing water
240 ppb ≈ 3.83 Gt
Human body
2.6·107 ppb ≈ 1.81 kg