8 nitrogen ← oxygen → fluorine - ↑ O ↓ S Periodic table - Extended periodic table
General
Name, symbol, number	oxygen, O, 8
Chemical series	nonmetals, chalcogens
Group, period, block	16, 2, p
Appearance	Liquid Oxygen
Standard atomic weight	15.9994(3) g·mol−1
Electron configuration	1s2 2s2 2p4
Electrons per shell	2, 6
Physical properties
Phase	gas
Density	(0 °C, 101.325 kPa) 1.429 g/L
Melting point	54.36 K (-218.79 °C, -361.82 °F)
Boiling point	90.20 K (-182.95 °C, -297.31 °F)
Critical point	154.59 K, 5.043 MPa
Heat of fusion	(O2) 0.444 kJ·mol−1
Heat of vaporization	(O2) 6.82 kJ·mol−1
Heat capacity	(25 °C) (O2) 29.378 J·mol−1·K−1
Vapor pressure P/Pa 1 10 100 1 k 10 k 100 k at T/K       61 73 90
Atomic properties
Crystal structure	cubic
Oxidation states	2, 1, −1, −2 (neutral oxide)
Electronegativity	3.44 (Pauling scale)
Ionization energies (more)	1st: 1313.9 kJ·mol−1
	2nd: 3388.3 kJ·mol−1
	3rd: 5300.5 kJ·mol−1
Atomic radius	60 pm
Atomic radius (calc.)	48 pm
Covalent radius	73 pm
Van der Waals radius	152 pm
Miscellaneous
Magnetic ordering	paramagnetic
Thermal conductivity	(300 K) 26.58x10-3  W·m−1·K−1
Speed of sound	(gas, 27 °C) 330 m/s
CAS registry number	7782-44-7
Selected isotopes
Main article: Isotopes of oxygen iso NA half-life DM DE (MeV) DP 16O 99.76% 16O is stable with 8 neutrons 17O 0.039% 17O is stable with 9 neutrons 18O 0.201% 18O is stable with 10 neutrons
References
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Oxygen is the element with atomic number 8 and represented by the symbol O. It is a member of the chalcogen group on the periodic table, and is a highly reactive nonmetallic period 2 element that readily forms compounds (notably oxides) with almost all other elements. At standard temperature and pressure two atoms of the element bind to form dioxygen, a colorless, odorless, tasteless diatomic gas with the formula O₂. Oxygen is the third most abundant element in the universe by mass after hydrogen and helium^[1] and the most abundant element by mass in the Earth's crust.^[2] Oxygen constitutes 88.8% of the mass of water and 20.9% of the volume of air.^[3] There are 4 known allotropes of oxygen: dioxygen, O2 - colorless ozone, O3 - blue tetraoxygen, O4 - red The common allotrope of elemental oxygen on Earth, O2, is known as dioxygen. ... Oxygen can refer to: Oxygen – Chemical element In medical usage - oxygen therapy Oxygen Network – Womens television network O2 – Mobile phone network Newspapers sometimes say oxygen cylinders as an inaccurate reference to scuba gear. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... Distinguished from fluorene and fluorone. ... This article is about the chemical element. ... This is a standard display of the periodic table of the elements. ... An extended periodic table was suggested by Glenn T. Seaborg in 1969. ... This is a list of chemical elements, sorted by name and color coded according to type of element. ... Categories: Chemical elements ... sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex sex... Together with the metals and metalloids, a nonmetal is one of three categories of chemical elements as distinguished by ionization and bonding properties. ... The chalcogens (with the ch pronounced with a hard c as in chemistry) are the name for the periodic table group 16 (old-style: VIB or VIA) in the periodic table. ... A group, also known as a family, is a vertical column in the periodic table of the chemical elements. ... In the periodic table of the elements, a period is a horizontal row of the table. ... A block of the periodic table of elements is a set of adjacent groups. ... The chalcogens are the name for the periodic table group 16 (old-style: VIB or VIA) in the periodic table. ... A period 2 element is one of the chemical elements in the second row (or period) of the periodic table of the elements. ... The p-block of the periodic table of elements consists of the last six groups. ... Color is an important part of the visual arts. ... Image File history File links Liquid_Oxygen. ... The atomic mass (ma) is the mass of an atom at rest, most often expressed in unified atomic mass units. ... To help compare different orders of magnitude, the following list describes various mass levels between 10−36 kg and 1053 kg. ... Hydrogen = 1 List of Elements in Atomic Number Order. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... Electron atomic and molecular orbitals In atomic physics and quantum chemistry, the electron configuration is the arrangement of electrons in an atom, molecule, or other physical structure (, a crystal). ... For other uses, see Electron (disambiguation). ... Example of a sodium electron shell model An electron shell, also known as a main energy level, is a group of atomic orbitals with the same value of the principal quantum number n. ... 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In physical chemistry, thermodynamics, chemistry and condensed matter physics, a critical point, also called a critical state, specifies the conditions (temperature, pressure) at which the liquid state of the matter ceases to exist. ... For other uses, see Kelvin (disambiguation). ... Standard enthalpy change of fusion of period three. ... Kilojoule per mole are an SI derived unit of energy per amount of material, where energy is measured in units of 1000 joules, and the amount of material is measured in mole units. ... The heat of vaporization is a physical property of substances. ... Kilojoule per mole are an SI derived unit of energy per amount of material, where energy is measured in units of 1000 joules, and the amount of material is measured in mole units. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Vapor pressure is the pressure of a vapor in equilibrium with its non-vapor phases. ... Enargite crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... Not to be confused with oxidation state. ... Oxygen difluoride is a chemical compound whose formula is OF2. ... Dioxygen difluoride, O2F2, has a density of 1. ... A peroxide is a compound containing an oxygen-oxygen single bond. ... Electronegativity is a measure of the ability of an atom or molecule to attract electrons in the context of a chemical bond. ... The ionization energy (IE) of an atom or of a molecule is the energy required to strip it of an electron. ... These tables list the ionization energy in kJ/mol necessary to remove an electron from a neutral atom (first energy), respectively from a singly, doubly, etc. ... Kilojoule per mole are an SI derived unit of energy per amount of material, where energy is measured in units of 1000 joules, and the amount of material is measured in mole units. ... Atomic radius: Ionic radius Covalent radius Metallic radius van der Waals radius edit Atomic radius, and more generally the size of an atom, is not a precisely defined physical quantity, nor is it constant in all circumstances. ... To help compare different orders of magnitude this page lists lengths between 10 pm and 100 pm (10-11 m and 10-12 m). ... One picometre is defined as 1x10-12 metres, in standard units. ... To help compare different orders of magnitude this page lists lengths between 10 pm and 100 pm (10-11 m and 10-12 m). ... Atomic radius: Ionic radius Covalent radius Metallic radius van der Waals radius edit The covalent radius, rcov, is a measure of the size of atom which forms part of a covalent bond. ... To help compare different orders of magnitude this page lists lengths between 10 pm and 100 pm (10-11 m and 10-12 m). ... The van der Waals radius of an atom is the radius of an imaginary hard sphere which can be used to model the atom for many purposes. ... You have big harry skanky balls ... For other senses of this word, see magnetism (disambiguation). ... Simple Illustration of a paramagnetic probe made up from miniature magnets. ... K value redirects here. ... This page is about the physical speed of sound waves in a medium. ... Metre per second (U.S. spelling: meter per second) is an SI derived unit of both speed (scalar) and velocity (vector), defined by distance in metres divided by time in seconds. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... Oxygen (O) Standard atomic mass: 15. ... For other uses, see Isotope (disambiguation). ... Natural abundance refers to the prevalence of different isotopes of an element as found in nature. ... Half-Life For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. ... In physics, the decay mode describes a particular way a particle decays. ... The decay energy is the energy released by a nuclear decay. ... The electronvolt (symbol eV) is a unit of energy. ... In nuclear physics, a decay product, also known as a daughter product, is a nuclide resulting from the radioactive decay of a parent or precursor nuclide. ... Stable isotopes are chemical isotopes that are not radioactive. ... This article or section does not adequately cite its references or sources. ... Stable isotopes are chemical isotopes that are not radioactive. ... This article or section does not adequately cite its references or sources. ... Oxygen-18 is a natural, stable isotope of oxygen and one of the environmental isotopes. ... Oxygen-18 is a natural, stable isotope of oxygen and one of the environmental isotopes. ... Oxygen-18 is a natural, stable isotope of oxygen and one of the environmental isotopes. ... Oxygen-18 is a natural, stable isotope of oxygen and one of the environmental isotopes. ... Stable isotopes are chemical isotopes that are not radioactive. ... This article or section does not adequately cite its references or sources. ... Recommended values for many properties of the elements, together with various references, are collected on these data pages. ... The periodic table of the chemical elements A chemical element, or element, is a type of atom that is defined by its atomic number; that is, by the number of protons in its nucleus. ... See also: List of elements by atomic number In chemistry and physics, the atomic number (also known as the proton number) is the number of protons found in the nucleus of an atom. ... The chalcogens (with the ch pronounced with a hard c as in chemistry) are the name for the periodic table group 16 (old-style: VIB or VIA) in the periodic table. ... A group, also known as a family, is a vertical column in the periodic table of the chemical elements. ... The Periodic Table redirects here. ... Together with the metals and metalloids, a nonmetal is one of three categories of chemical elements as distinguished by ionization and bonding properties. ... A period 2 element is one of the chemical elements in the second row (or period) of the periodic table of the elements. ... Look up chemical compound in Wiktionary, the free dictionary. ... An oxide is a chemical compound containing at least one oxygen atom and other elements. ... Temperature and air pressure can vary from one place to another on the Earth, and can also vary in the same place with time. ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ... A space-filling model of the diatomic molecule dinitrogen, N2. ... Gas phase particles (atoms, molecules, or ions) move around freely Gas is one of the four major states of matter, consisting of freely moving atoms or molecules without a definite shape and without a definite volume. ... The abundance of a chemical element measures how relatively common the element is, or how much of the element there is by comparison to all other elements. ... This article is about the chemistry of hydrogen. ... General Name, symbol, number helium, He, 2 Chemical series noble gases Group, period, block 18, 1, s Appearance colorless Standard atomic weight 4. ... << Chemical elements data references // Earth bulk continental crust and upper continental crust C1 — Crust: CRC Handbook C2 — Crust: Kaye & Laby C3 — Crust: Greenwood C4 — Crust: Ahrens (Taylor) C5 — Crust: Ahrens (Wänke) C6 — Crust: Ahrens (Weaver) U1 — Upper crust: Ahrens (Taylor) U2 — Upper crust: Ahrens (Shaw) Mass fraction, in kg... Earth cutaway from core to exosphere. ... Air redirects here. ...

All major classes of structural molecules in living organisms, such as proteins, carbohydrates, and fats, contain oxygen, as do the major inorganic compounds that comprise animal shells, teeth, and bone. Oxygen in the form of O₂ is produced from water by cyanobacteria, algae and plants during photosynthesis and is used in cellular respiration for all complex life. Oxygen is toxic to anaerobic organisms, which were the dominant form of early life on Earth until O₂ began to accumulate in the atmosphere 2.5 billion years ago.^[4] Another form (allotrope) of oxygen, ozone (O₃), helps protect the biosphere from ultraviolet radiation with the high-altitude ozone layer, but is a pollutant near the surface where it is a by-product of smog. A representation of the 3D structure of myoglobin showing coloured alpha helices. ... Lactose is a disaccharide found in milk. ... For other uses, see FAT. Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. ... Traditionally, inorganic compounds are considered to be of mineral, not biological, origin. ... Orders The taxonomy is currently under revision. ... Osborne (talk) 20:17, 5 December 2007 (UTC):For the programming language, see algae (programming language) Laurencia, a marine red alga from Hawaii. ... The leaf is the primary site of photosynthesis in plants. ... Cellular respiration was discovered by mad scientist Mr. ... Aerobic and anaerobic bacteria can be identified by growning them in liquid culture: 1: Obligate aerobic bacteria gather at the top of the test tube in order to absorb maximal amount of oxygen. ... The evolutionary history of life and the origin of life are fields of ongoing geological and biological research. ... There are 4 known allotropes of oxygen: dioxygen, O2 - colorless ozone, O3 - blue tetraoxygen, O4 - red The common allotrope of elemental oxygen on Earth, O2, is known as dioxygen. ... For other uses, see Ozone (disambiguation). ... Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... The ozone layer is a layer in Earths atmosphere which contains relatively high concentrations of ozone (O3). ... For other uses, see Smog (disambiguation). ...

Oxygen was independently discovered by Joseph Priestley and Carl Wilhelm Scheele in the 1770s, but Priestley is usually given priority because he published his findings first. The name oxygen was coined in 1777 by Antoine Lavoisier,^[5] whose experiments with oxygen helped to discredit the then-popular phlogiston theory of combustion and corrosion. Oxygen is produced industrially by fractional distillation of liquefied air, use of zeolites to remove carbon dioxide and nitrogen from air, electrolysis of water and other means. Uses of oxygen include the production of steel, plastics and textiles; rocket propellant; oxygen therapy; and life support in aircraft, submarines, spaceflight and diving. Priestley by Ellen Sharples (1794)[1] Joseph Priestley (March 13, 1733 (old style) – February 8, 1804) was an eighteenth-century British natural philosopher, Dissenting clergyman, political theorist, theologian, and educator. ... Carl Wilhelm Scheele Scheeles house with his pharmacy in Köping. ... Antoine-Laurent de Lavoisier (August 26, 1743 – May 8, 1794), the father of modern chemistry [1], was a French nobleman prominent in the histories of chemistry, finance, biology, and economics. ... Phlogiston theory was a 17th century attempt to explain oxidation processes, such as fire and rust. ... This article is about the chemical reaction combustion. ... For the hazard, see corrosive. ... Fractional distillation is the separation of a mixture into its component parts, or fractions, such as in separating chemical compounds by their boiling point by heating them to a temperature at which several fractions of the compound will evaporate. ... Zeolite The micro-porous molecular structure of a zeolite, ZSM-5 Zeolites (Greek, zein, to boil; lithos, a stone) are minerals that have a micro-porous structure. ... Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... Hoffman voltameter used to electrolyze water. ... Rocket propellants undergo exothermic chemical reactions which produce hot gas which is used by a rocket for propulsive purposes. ... Oxygen first aid kit showing a demand valve and a constant flow mask Oxygen therapy is the administration of oxygen as a therapeutic modality. ... Edward White on a spacewalk during the Gemini 4 mission. ... It has been suggested that this article or section be merged with Professional diving. ...

Characteristics

Structure

Electron shell diagram of oxygen

At standard temperature and pressure, oxygen is a colorless, odorless gas with the molecular formula O₂, in which the two oxygen atoms are chemically bonded to each other with a spin triplet electron configuration. This bond has a bond order of two, and is often over-simplified in description as a double bond.^[6] Temperature and air pressure can vary from one place to another on the Earth, and can also vary in the same place with time. ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ... In physics, spin is the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ... Electron atomic and molecular orbitals In atomic physics and quantum chemistry, the electron configuration is the arrangement of electrons in an atom, molecule, or other physical structure (, a crystal). ... Bond order is the number of bonds between a pair of atoms. ... Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. ...

Triplet oxygen is the ground state of the O₂ molecule.^[7] The electron configuration of the molecule has two unpaired electrons occupying two degenerate molecular orbitals.^[8] These orbitals are classified as antibonding (weakening the bond order from three to two), so the diatomic oxygen bond is weaker than the diatomic nitrogen triple bond in which all bonding molecular orbitals are filled, but some antibonding orbitals are not.^[7] Triplet oxygen is the ground state of the oxygen molecule. ... In physics, the ground state of a quantum mechanical system is its lowest-energy state. ... Degenerate orbitals for electrons in an atomic subshell are orbitals at identical energy levels (by definition). ... In chemistry, a molecular orbital is a region in which an electron may be found in a molecule. ... Antibonding (or anti-bonding) is a type of chemical bonding. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ...

In normal triplet form, O₂ molecules are paramagnetic—they form a magnet in the presence of a magnetic field—because of the spin magnetic moments of the unpaired electrons in the molecule, and the negative exchange energy between neighboring O₂ molecules.^[9] Liquid oxygen is attracted to a magnet to a sufficient extent that, in laboratory demonstrations, a bridge of liquid oxygen may be supported against its own weight between the poles of a powerful magnet.^[10][11] Simple Illustration of a paramagnetic probe made up from miniature magnets. ... In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ... A bar magnet. ... Exchange interaction is the quantum mechanical effect of increasing or decreasing the energy of two or more fermions when their wave functions overlap. ... For other uses, see Magnet (disambiguation). ...

Singlet oxygen, a name given to several higher-energy species of molecular O₂ in which all the electron spins are paired, is much more reactive towards common organic molecules. In nature, singlet oxygen is commonly formed from water during photosynthesis, using the energy of sunlight.^[12] It is also produced in the troposphere by the photolysis of ozone by light of short wavelength,^[13] and by the immune system as a source of active oxygen.^[14] Carotenoids in photosynthetic organisms (and possibly also in animals) play a major role in absorbing energy from singlet oxygen and converting it to the unexcited ground state before it can cause harm to tissues.^[15] Molecular orbital diagram for singlet oxygen. ... Benzene is the simplest of the arenes, a family of organic compounds An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. ... Atmosphere diagram showing the mesosphere and other layers. ... The orange ring surrounding Grand Prismatic Spring is due to carotenoid molecules, produced by huge mats of algae and bacteria. ...

Allotropes

Main article: Allotropes of oxygen

Ozone is a rare gas on Earth found mostly in the stratosphere.

The common allotrope of elemental oxygen on Earth is called dioxygen, O₂. It has a bond length of 121 pm and a bond energy of 498 kJ·mol^-1.^[16] This is the form that is used by complex forms of life, such as animals, in cellular respiration (see Biological role) and is the form that is a major part of the Earth's atmosphere (see Occurrence). Other aspects of O₂ are covered in the remainder of this article. There are 4 known allotropes of oxygen: dioxygen, O2 - colorless ozone, O3 - blue tetraoxygen, O4 - red The common allotrope of elemental oxygen on Earth, O2, is known as dioxygen. ... Image File history File links Download high resolution version (1089x1817, 228 KB) File links The following pages link to this file: Oxygen ... Image File history File links Download high resolution version (1089x1817, 228 KB) File links The following pages link to this file: Oxygen ... Atmosphere diagram showing stratosphere. ... Diamond and graphite are two allotropes of carbon: pure forms of the same element that differ in structure. ... One picometre is defined as 1x10-12 metres, in standard units. ... The joule per mole (symbol: J·mol-1) is an SI derived unit of energy per amount of material. ... Cellular respiration was discovered by mad scientist Mr. ...

Trioxygen (O₃) is usually known as ozone and is a very reactive allotrope of oxygen that is damaging to lung tissue.^[17] Ozone is produced in the upper atmosphere when O₂ combines with atomic oxygen made by the splitting of O₂ by ultraviolet (UV) radiation.^[5] Since ozone absorbs strongly in the UV region of the spectrum, it functions as a protective radiation shield for the planet (see ozone layer).^[5] Near the earth's surface, however, it is a pollutant formed as a by-product of automobile exhaust.^[18] For other uses, see Ozone (disambiguation). ... Earths atmosphere is the layer of gases surrounding the planet Earth and retained by the Earths gravity. ... For other uses, see Ultraviolet (disambiguation). ... Legend γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultra high frequency VHF = Very high frequency HF = High... The ozone layer is a layer in Earths atmosphere which contains relatively high concentrations of ozone (O3). ... Air pollution is the modification of the natural characteristics of the atmosphere by a chemical, particulate matter, or biological agent. ...

The metastable molecule tetraoxygen (O₄) was discovered in 2001,^[19][20] and was assumed to exist in one of the six phases of solid oxygen. It was proven in 2006 that that phase, created by pressurizing O₂ to 20 GPa, is in fact a rhombohedral O₈ cluster.^[21] This cluster has the potential to be a much more powerful oxidizer than either O₂ or O₃ and may therefore be used in rocket fuel.^[19][20] A metallic phase was discovered in 1990 when solid oxygen is subjected to a pressure of above 96 GPa^[22] and it was shown in 1998 that at very low temperatures, this phase becomes superconducting.^[23] Metastability in molecules is the ability of a non-equilibrium chemical state to persist for a long period of time. ... Tetraoxygen, also called red oxygen (O4), is an allotrope of oxygen occuring in extremely high pressures (in order of 20 GPa). ... It has been suggested that this article or section be merged with Oxygen. ... For other uses, see Pascal. ... In crystallography, the rhombohedral (or trigonal) crystal system is one of the 7 lattice point groups. ... In chemistry, a cluster is an ensemble of bound atoms intermediate in size between a molecule and a bulk solid. ... European Union Chemical hazard symbol for oxidizing agents Dangerous goods label for oxidizing agents Oxidizing agent placard An oxidizing agent (also called an oxidant or oxidizer) is A chemical compound that readily transfers oxygen atoms or A substance that gains electrons in a redox chemical reaction. ... Rocket fuel is a propellant that reacts with an oxidizing agent to produce thrust in a rocket. ... A magnet levitating above a high-temperature superconductor, cooled with liquid nitrogen. ...

Physical properties

See also: Liquid oxygen and solid oxygen

Oxygen is more soluble in water than nitrogen; water contains approximately 1 molecule of O₂ for every 2 molecules of N₂, compared to an atmospheric ratio of approximately 1:4. The solubility of oxygen in water is temperature-dependent, and about twice as much (14.6 mg·L⁻¹) dissolves at 0 °C than at 20 °C (7.6 mg·L⁻¹).^[24][25] At 25 °C and 1 atm of air, freshwater contains about 6.04 milliliters (mL) of oxygen per liter, whereas seawater contains about 4.95 mL per liter.^[26] At 5 °C the solubility increases to 9.0 mL (50% more than at 25 °C) per liter for water and 7.2 mL (45% more) per liter for sea water. This article does not cite any references or sources. ... It has been suggested that this article or section be merged with Oxygen. ... Solubility is a chemical property referring to the ability for a given substance, the solute, to dissolve in a solvent. ... Standard atmosphere (symbol: atm) is a unit of pressure. ... The litre or liter (see spelling differences) is a unit of volume. ... The liter (spelled liter in American English and litre in Commonwealth English) is a unit of volume. ... Annual mean sea surface salinity for the World Ocean. ...

Oxygen condenses at 90.20 K (−182.95 °C, −297.31 °F), and freezes at 54.36 K (−218.79 °C, −361.82 °F).^[27] Both liquid and solid O₂ are clear substances with a light sky-blue color caused by absorption in the red (in contrast with the blue color of the sky, which is due to Rayleigh scattering of blue light). High-purity liquid O₂ is usually obtained by the fractional distillation of liquefied air;^[28] Liquid oxygen may also be produced by condensation out of air, using liquid nitrogen as a coolant. It is a highly-reactive substance and must be segregated from combustible materials.^[29] For other uses, see Kelvin (disambiguation). ... This article does not cite any references or sources. ... It has been suggested that this article or section be merged with Oxygen. ... Spectrum of blue sky clearly showing solar Fraunhofer lines and atmospheric water absorption band. ... Rayleigh scattering causing the blue hue of the sky and the reddening at sunset Rayleigh scattering (named after Lord Rayleigh) is the scattering of light, or other electromagnetic radiation, by particles much smaller than the wavelength of the light. ... Fractional distillation is the separation of a mixture into its component parts, or fractions, such as in separating chemical compounds by their boiling point by heating them to a temperature at which several fractions of the compound will evaporate. ...

Isotopes and stellar origin

Late in a massive star's life, ¹⁶O concentrates in the O-shell, ¹⁷O in the H-shell and ¹⁸O in the He-shell.

Main article: Isotopes of oxygen

Naturally occurring oxygen is composed of three stable isotopes, ¹⁶O, ¹⁷O, and ¹⁸O, with ¹⁶O being the most abundant (99.762% natural abundance).^[30] Oxygen isotopes range in mass number from 12 to 28.^[30] Image File history File links Evolved_star_fusion_shells. ... Image File history File links Evolved_star_fusion_shells. ... Oxygen-18 is a natural, stable isotope of oxygen and one of the environmental isotopes. ... Oxygen (O) Standard atomic mass: 15. ... For other uses, see Isotope (disambiguation). ... Oxygen-18 is a natural, stable isotope of oxygen and one of the environmental isotopes. ... Natural abundance refers to the prevalence of different isotopes of an element as found in nature. ... The mass number (A), also called atomic mass number (not to be confused with atomic number (Z) which denotes the number of protons in a nucleus) or nucleon number, is the number of nucleons (protons and neutrons) in an atomic nucleus. ...

Most ¹⁶O is synthesized at the end of the helium fusion process in stars but some is made in the neon burning process.^{[31] 17}O is primarily made by the burning of hydrogen into helium during the CNO cycle, making it a common isotope in the hydrogen burning zones of stars.^[31] Most ¹⁸O is produced when ¹⁴N (made abundant from CNO burning) captures a ⁴He nucleus, making ¹⁸O common in the helium-rich zones of stars.^[31] Nucleosynthesis is the process of creating new atomic nuclei from preexisting nucleons (protons and neutrons). ... Helium fusion is a kind of nuclear fusion, with the nuclei involved being helium. ... This article is about the astronomical object. ... Neon burning process is a set of nuclear fusion reactions that take place in massive stars (at least 8 MSun). ... General Name, symbol, number helium, He, 2 Chemical series noble gases Group, period, block 18, 1, s Appearance colorless Standard atomic weight 4. ... This article does not cite its references or sources. ... Nitrogen-14 is a stable, non-radioactive isotope of the nitrogen element. ... Helium-4 is a non-radioactive and light isotope of helium. ...

Fourteen radioisotopes have been characterized, the most stable being ¹⁵O with a half-life of 122.24 seconds (s) and ¹⁴O with a half-life of 70.606 s.^[30] All of the remaining radioactive isotopes have half-lives that are less than 27 s and the majority of these have half-lives that are less than 83 milliseconds.^[30] The most common decay mode of the isotopes lighter than ¹⁶O is electron capture to yield nitrogen, and the most common mode for the isotopes heavier than ¹⁸O is beta decay to yield fluorine.^[30] A radionuclide is an atom with an unstable nucleus. ... Half-Life For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. ... Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... In physics, the decay mode describes a particular way a particle decays. ... Electron capture is a decay mode for isotopes that will occur when there are too many protons in the nucleus of an atom, and there isnt enough energy to emit a positron; however, it continues to be a viable decay mode for radioactive isotopes that can decay by positron... In nuclear physics, beta decay (sometimes called neutron decay) is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. ... Distinguished from fluorene and fluorone. ...

Occurrence

See also: Silicate minerals and Category:Oxide minerals

Oxygen is the third most abundant chemical element in the universe, after hydrogen and helium.^[1] About 0.9% of the Sun's mass is oxygen.^[3] Oxygen constitutes 49.2% of the Earth's crust by mass^[2] and is the major component of the world's oceans (88.8% by mass).^[3] It is the second most common component of the Earth's atmosphere, taking up 21.0% of its volume and 23.1% of its mass (some 10¹⁵ tonnes).^[32][3][33] Earth is unusual among the planets of the Solar System in having such a high concentration of oxygen gas in its atmosphere: Mars (with 0.1% O₂ by volume) and Venus have far lower concentrations. However, the O₂ surrounding these other planets is produced solely by ultraviolet radiation impacting oxygen-containing molecules such as carbon dioxide. The silicate minerals make up the largest and most important class of rock-forming minerals. ... Sol redirects here. ... Earth cutaway from core to exosphere. ... Air redirects here. ... This article is about the Solar System. ... Adjectives: Martian Atmosphere Surface pressure: 0. ... For other uses, see Venus (disambiguation). ... Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ...

Cold water holds more dissolved O₂.

The unusually high concentration of oxygen on Earth is the result of the oxygen cycle. This biogeochemical cycle describes the movement of oxygen within and between its three main reservoirs on Earth: the atmosphere, the biosphere, and the lithosphere. The main driving factor of the oxygen cycle is photosynthesis, which is responsible for modern Earth's atmosphere. Because of the vast amounts of oxygen gas available in the atmosphere, even if all photosynthesis were to cease completely, it would take all the oxygen-consuming processes at the present rate at least another 5,000 years to strip all the O₂ from the atmosphere.^[34][35] Image File history File links Download high resolution version (1525x1075, 296 KB) Summary Annual mean sea surface dissolved oxygen (O2) from the World Ocean Atlas 2001. ... Image File history File links Download high resolution version (1525x1075, 296 KB) Summary Annual mean sea surface dissolved oxygen (O2) from the World Ocean Atlas 2001. ... the oxygen cycle The oxygen cycle is the biogeochemical cycle that describes the movement of oxygen within and between its three main reservoirs: the atmosphere, the biosphere, and the lithosphere. ... In ecology, a biogeochemical cycle is a circuit where a nutrient moves back and forth between both biotic and abiotic components of ecosystems. ... For other uses, see Biosphere (disambiguation). ... The tectonic plates of the lithosphere on Earth. ... The leaf is the primary site of photosynthesis in plants. ...

Free oxygen also occurs in solution in the world's water bodies. The increased solubility of O₂ at lower temperatures (see Physical properties) has important implications for ocean life, as polar oceans support a much higher density of life due to their higher oxygen content.^[36] Polluted water may have reduced amounts of O₂ in it, depleted by decaying algae and other biomaterials (see eutrophication). Scientists assess this aspect of water quality by measuring the water's biochemical oxygen demand, or the amount of O₂ needed to restore it to a normal concentration.^[37] Raw sewage and industrial waste flows into the U.S. from Mexico as the New River passes from Mexicali, Baja California to Calexico, California Water pollution is a large set of adverse effects upon water bodies such as lakes, rivers, oceans, and groundwater caused by human activities. ... Eutrophication, strictly speaking, means an increase in chemical nutrients -- typically compounds containing nitrogen or phosphorus -- in an ecosystem. ... This article or section does not cite any references or sources. ...

Biological role

Main article: Dioxygen in biological reactions

Photosynthesis and respiration

Oxygen evolution by water oxidation during photosynthesis. The jagged lines represent four photons oxidizing the central cluster of the oxygen evolving complex by exciting and removing four electrons through a cycle of S-states.

In nature, free oxygen is produced by the light-driven splitting of water during oxygenic photosynthesis. Green algae and cyanobacteria in marine environments provide about 70% of the free oxygen produced on earth and the rest is produced by terrestrial plants.^[38] Image File history File links Oxygen_evolving_complex. ... Image File history File links Oxygen_evolving_complex. ... Oxygen evolving complex. ... Photolysis refers to any chemical reaction in which a compound is broken down by light. ... The leaf is the primary site of photosynthesis in plants. ... Divisions Chlorophyta Charophyta Green algae are microscopic protists; found in all aquatic environments, including marine, freshwater and brackish water. ... Orders The taxonomy is currently under revision. ...

A simplified overall formula for photosynthesis is:^[39]

6CO₂ + 6H₂O + photons → C₆H₁₂O₆ + 6O₂ (or simply carbon dioxide + water + sunlight → glucose + dioxygen)

Photolytic oxygen evolution occurs in the thylakoid membranes of photosynthetic organisms and requires the energy of four photons.^[40] Many steps are involved, but the result is the formation of a proton gradient across the thylakoid membrane, which is used to synthesize ATP via photophosphorylation.^[41] The O₂ remaining after oxidation of the water molecule is released into the atmosphere.^[42] In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... Oxygen evolution is the process of generating molecular oxygen through chemical reaction. ... A thylakoid is a phospholipid bilayer membrane internal to chloroplasts. ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... For other uses, see Proton (disambiguation). ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... The production of ATP using the energy of sunlight is called photophosphorylation. ...

Molecular dioxygen, O₂, is essential for cellular respiration in all aerobic organisms. Oxygen is used in mitochondria to help generate adenosine triphosphate (ATP) during oxidative phosphorylation. The reaction for aerobic respiration is essentially the reverse of photosynthesis and is simplified as: Cellular respiration was discovered by mad scientist Mr. ... Aerobic and anaerobic bacteria can be identified by growning them in liquid culture: 1: Obligate aerobic bacteria gather at the top of the test tube in order to absorb maximal amount of oxygen. ... Electron micrograph of a mitochondrion showing its mitochondrial matrix and membranes In cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed organelle that is found in most eukaryotic cells. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... The electron transport chain in the mitochondrion is the site of oxidative phosphorylation in eukaryotes. ...

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 2880 kJ·mol^-1

In vertebrates, O₂ is diffused through membranes in the lungs and into red blood cells. Hemoglobin binds O₂, changing its color from bluish red to bright red.^[43][17] Other animals use hemocyanin (molluscs and some arthropods) or hemerythrin (spiders and lobsters).^[32] A liter of blood can dissolve 200 cc of O₂.^[32] This article does not cite any references or sources. ... diffusion (disambiguation). ... “Red cell” redirects here. ... Structure of hemoglobin. ... Single Oxygenated Hemocyanin protein from Octopus Hemocyanins (also spelled haemocyanins) are respiratory proteins containing two copper atoms that reversibly bind a single oxygen molecule (O2). ... Classes Caudofoveata Aplacophora Polyplacophora Monoplacophora Bivalvia Scaphopoda Gastropoda Cephalopoda † Rostroconchia † Helcionelloida † ?Bellerophontida The molluscs (British spelling) or mollusks (American spelling) are members of the very large and diverse phylum Mollusca. ... Subphyla and Classes Subphylum Trilobitomorpha Trilobita - trilobites (extinct) Subphylum Chelicerata Arachnida - spiders,scorpions, etc. ... Single Oxygenated Hemerythrin protein Trimeric Hemerythrin Protein Complex Hemerythrin (also spelled haemerythrin; from Greek words αίμα = blood and ερυθρός = red) is an oligomeric protein responsible for oxygen (O2) transportation in the marine invertebrate phyla of sipunculids, priapulids, brachiopods, and in a single annelid worm, magelona. ... For other uses, see Spider (disambiguation). ... Subfamilies and Genera Neophoberinae Acanthacaris Thymopinae Nephropsis Nephropides Thymops Thymopsis Nephropinae Homarus Nephrops Homarinus Metanephrops Eunephrops Thymopides Clawed lobsters comprise a family (Nephropidae, sometimes also Homaridae) of large marine crustaceans. ...

Reactive oxygen species, such as superoxide ion (O₂⁻) and hydrogen peroxide (H₂O₂), are dangerous by-products of oxygen use in organisms.^[32] Parts of the immune system of higher organisms, however, create peroxide, superoxide, and singlet oxygen to destroy invading microbes. Reactive oxygen species also play an important role in the hypersensitive response of plants against pathogen attack.^[41] Reactive oxygen species (ROS) include oxygen ions, free radicals and peroxides both inorganic and organic. ... Lewis electron configuration of superoxide. ... R-phrases , , , , S-phrases , , , , , , , , Flash point Non-flammable Related Compounds Related compounds Water Ozone Hydrazine Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colorless in... A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange). ... The hypersensitive response (HR) is a mechanism, used by plants, to prevent the spread of infection by microbial pathogens. ...

Build-up in the atmosphere