Nitrogen

Nitrogen,  ₇N

General properties
Appearance	colorless gas, liquid or solid
Standard atomic weight (Ar, standard)	[7001140064300000000♠14.00643, 7001140072800000000♠14.00728] conventional: 7001140070000000000♠14.007
Nitrogen in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson – ↑ N ↓ P carbon ← nitrogen → oxygen
Atomic number (Z)	7
Group	group 15 (pnictogens)
Period	period 2
Element category	diatomic nonmetal
Block	p-block
Electron configuration	[He] 2s2 2p3
Electrons per shell	2, 5
Physical properties
Phase at STP	gas
Melting point	63.15 K ​(−210.00 °C, ​−346.00 °F)
Boiling point	77.355 K ​(−195.795 °C, ​−320.431 °F)
Density (at STP)	1.2504 g/L at 0 °C, 1013 mbar
when liquid (at b.p.)	0.808 g/cm3
Triple point	63.151 K, ​12.52 kPa
Critical point	126.192 K, 3.3958 MPa
Heat of fusion	(N2) 0.72 kJ/mol
Heat of vaporisation	(N2) 5.56 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	5, 4, 3, 2, 1, −1, −2, −3 ​(a strongly acidic oxide)
Electronegativity	Pauling scale: 3.04
Ionisation energies	1st: 1402.3 kJ/mol 2nd: 2856 kJ/mol 3rd: 4578.1 kJ/mol (more)
Covalent radius	71±1 pm
Van der Waals radius	155 pm
Spectral lines
Miscellanea
Crystal structure	​hexagonal
Speed of sound	353 m/s (gas, at 27 °C)
Thermal conductivity	25.83×10−3 W/(m·K)
Magnetic ordering	diamagnetic
CAS Number	17778-88-0 7727-37-9 (N2)
History
Discovery	Daniel Rutherford (1772)
Named by	Jean-Antoine Chaptal (1790)
Main isotopes of nitrogen
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct 13N syn 9.965 min ε 13C 14N 99.6% stable 15N 0.4% stable
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Nitrogen is a chemical element with symbol N and atomic number 7. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772. Although Carl Wilhelm Scheele and Henry Cavendish had independently done so at about the same time, Rutherford is generally accorded the credit because his work was published first. 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 Greek άζωτικός "no life", as it is an asphyxiant gas; this name is instead used in many languages, such as French, Russian, and Turkish, and appears in the English names of some nitrogen compounds such as hydrazine, azides and azo compounds.

Nitrogen is the lightest member of group 15 of the periodic table, often called the pnictogens. The name comes from the Greek πνίγειν "to choke", directly referencing nitrogen's asphyxiating properties. It is a common element in the universe, estimated at about seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bind to form dinitrogen, a colourless and odorless diatomic gas with the formula N₂. Dinitrogen forms about 78% of Earth's atmosphere, making it the most abundant uncombined element. 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 movement of the element from the air, into the biosphere and organic compounds, then back into the atmosphere.

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 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 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.