Oxygen

Joseph Priestley is usually given priority in the discovery.
Antoine Lavoisier discredited the phlogiston theory.
Robert H. Goddard and a liquid oxygen-gasoline rocket
An experiment setup for preparation of oxygen in academic laboratories
Orbital diagram, after Barrett (2002), showing the participating atomic orbitals from each oxygen atom, the molecular orbitals that result from their overlap, and the aufbau filling of the orbitals with the 12 electrons, 6 from each O atom, beginning from the lowest-energy orbitals, and resulting in covalent double-bond character from filled orbitals (and cancellation of the contributions of the pairs of σ and σ* and π and π* orbital pairs).
Liquid oxygen, temporarily suspended in a magnet owing to its paramagnetism
Space-filling model representation of dioxygen (O2) molecule
Oxygen discharge (spectrum) tube
Late in a massive star's life, 16O concentrates in the O-shell, 17O in the H-shell and 18O in the He-shell.
Cold water holds more dissolved.
500 million years of climate change vs. 18O
Photosynthesis splits water to liberate and fixes into sugar in what is called a Calvin cycle.
build-up in Earth's atmosphere: 1) no produced; 2) produced, but absorbed in oceans & seabed rock; 3)  starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4–5)  sinks filled and the gas accumulates
Hofmann electrolysis apparatus used in electrolysis of water.
Oxygen and MAPP gas compressed-gas cylinders with regulators
An oxygen concentrator in an emphysema patient's house
Low pressure pure is used in space suits.
Most commercially produced is used to smelt and/or decarburize iron.
Water is the most familiar oxygen compound.
Oxides, such as iron oxide or rust, form when oxygen combines with other elements.
Main symptoms of oxygen toxicity
The interior of the Apollo 1 Command Module. Pure at higher than normal pressure and a spark led to a fire and the loss of the Apollo 1 crew.

Chemical element with the symbol O and atomic number 8.

- Oxygen
Joseph Priestley is usually given priority in the discovery.

500 related topics

Relevance

Steam and liquid water are two different forms of the same chemical (pure) substance: water.

Chemical compound

Chemical substance composed of many identical molecules composed of atoms from more than one element held together by chemical bonds.

Chemical substance composed of many identical molecules composed of atoms from more than one element held together by chemical bonds.

Steam and liquid water are two different forms of the same chemical (pure) substance: water.

For example, a water molecule has formula H2O indicating two hydrogen atoms bonded to one oxygen atom.

Drifting smoke particles indicate the movement of the surrounding gas.

Gas

One of the four fundamental states of matter .

One of the four fundamental states of matter .

Drifting smoke particles indicate the movement of the surrounding gas.
Shuttle imagery of re-entry phase
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Random motion of gas particles results in diffusion.
21 April 1990 eruption of Mount Redoubt, Alaska, illustrating real gases not in thermodynamic equilibrium.
Boyle's equipment
Dalton's notation.
Compressibility factors for air.
Satellite view of weather pattern in vicinity of Robinson Crusoe Islands on 15 September 1999, shows a turbulent cloud pattern called a Kármán vortex street
Delta wing in wind tunnel. The shadows form as the indices of refraction change within the gas as it compresses on the leading edge of this wing.

A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or compound molecules made from a variety of atoms (e.g. carbon dioxide).

Lactose is a disaccharide found in animal milk. It consists of a molecule of D-galactose and a molecule of D-glucose bonded by beta-1-4 glycosidic linkage.

Carbohydrate

Lactose is a disaccharide found in animal milk. It consists of a molecule of D-galactose and a molecule of D-glucose bonded by beta-1-4 glycosidic linkage.
D-glucose is an aldohexose with the formula (C·H2O)6. The red atoms highlight the aldehyde group and the blue atoms highlight the asymmetric center furthest from the aldehyde; because this -OH is on the right of the Fischer projection, this is a D sugar.
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Glucose can exist in both a straight-chain and ring form.
Sucrose, also known as table sugar, is a common disaccharide. It is composed of two monosaccharides: D-glucose (left) and D-fructose (right).
Grain products: rich sources of carbohydrates
Glucose tablets

A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula Cm(H2O)n (where m may or may not be different from n).

Abundance (atom fraction) of the chemical elements in Earth's upper continental crust as a function of atomic number. The rarest elements in the crust (shown in yellow) are rare due to a combination of factors: all but one are the densest siderophiles (iron-loving) elements in the Goldschmidt classification, meaning they have a tendency to mix well with metallic iron, depleting them by being relocated deeper into the Earth's core. Their abundance in meteoroids is higher. Additionally, tellurium has been depleted by preaccretional sorting in the nebula via formation of volatile hydrogen telluride.

Abundance of the chemical elements

Measure of the occurrence of the chemical elements relative to all other elements in a given environment.

Measure of the occurrence of the chemical elements relative to all other elements in a given environment.

Abundance (atom fraction) of the chemical elements in Earth's upper continental crust as a function of atomic number. The rarest elements in the crust (shown in yellow) are rare due to a combination of factors: all but one are the densest siderophiles (iron-loving) elements in the Goldschmidt classification, meaning they have a tendency to mix well with metallic iron, depleting them by being relocated deeper into the Earth's core. Their abundance in meteoroids is higher. Additionally, tellurium has been depleted by preaccretional sorting in the nebula via formation of volatile hydrogen telluride.

For example, the abundance of oxygen in pure water can be measured in two ways: the mass fraction is about 89%, because that is the fraction of water's mass which is oxygen.

A space-filling model of the diatomic molecule dinitrogen, N2

Diatomic molecule

Diatomic molecules are molecules composed of only two atoms, of the same or different chemical elements.

Diatomic molecules are molecules composed of only two atoms, of the same or different chemical elements.

A space-filling model of the diatomic molecule dinitrogen, N2
A periodic table showing the elements that exist as homonuclear diatomic molecules under typical laboratory conditions.

If a diatomic molecule consists of two atoms of the same element, such as hydrogen (H2) or oxygen (O2), then it is said to be homonuclear.

NASA photo showing Earth's atmosphere at sunset, with Earth silhouetted

Atmosphere of Earth

Layer of gases retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere.

Layer of gases retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere.

NASA photo showing Earth's atmosphere at sunset, with Earth silhouetted
Composition of Earth's atmosphere by molecular count, excluding water vapor. Lower pie represents trace gases that together compose about 0.0434% of the atmosphere (0.0442% at August 2021 concentrations ). Numbers are mainly from 2000, with and methane from 2019, and do not represent any single source.
Mean atmospheric water vapor
The mole fraction of the main constituents of the Earth's atmosphere as a function of height according to the MSIS-E-90 atmospheric model.
Earth's atmosphere Lower 4 layers of the atmosphere in 3 dimensions as seen diagonally from above the exobase. Layers drawn to scale, objects within the layers are not to scale. Aurorae shown here at the bottom of the thermosphere can actually form at any altitude in this atmospheric layer.
orbiting in the thermosphere. Because of the angle of the photo, it appears to straddle the stratosphere and mesosphere that actually lie more than 250 km below. The orange layer is the troposphere, which gives way to the whitish stratosphere and then the blue mesosphere.
Temperature trends in two thick layers of the atmosphere as measured between January 1979 and December 2005 by microwave sounding units and advanced microwave sounding units on NOAA weather satellites. The instruments record microwaves emitted from oxygen molecules in the atmosphere. Source:
Temperature and mass density against altitude from the NRLMSISE-00 standard atmosphere model (the eight dotted lines in each "decade" are at the eight cubes 8, 27, 64, ..., 729)
Rough plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including visible light.
Distortive effect of atmospheric refraction upon the shape of the sun at the horizon.
An idealised view of three pairs of large circulation cells.
Oxygen content of the atmosphere over the last billion years

By mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases.

Christian Friedrich Schönbein (18 October 1799 – 29 August 1868)

Ozone

Inorganic molecule with the chemical formula .

Inorganic molecule with the chemical formula .

Christian Friedrich Schönbein (18 October 1799 – 29 August 1868)
A prototype ozonometer built by John Smyth in 1865
Resonance Lewis structures of the ozone molecule
General reaction equation of ozonolysis
The distribution of atmospheric ozone in partial pressure as a function of altitude
Concentration of ozone as measured by the Nimbus-7 satellite
Total ozone concentration in June 2000 as measured by the NASA EP-TOMS satellite instrument
Levels of ozone at various altitudes and blocking of different bands of ultraviolet radiation. Essentially all UVC (100–280 nm) is blocked by dioxygen (at 100–200 nm) or by ozone (at 200–280 nm) in the atmosphere. The shorter portion of this band and even more energetic UV causes the formation of the ozone layer, when single oxygen atoms produced by UV photolysis of dioxygen (below 240 nm) react with more dioxygen. The ozone layer itself then blocks most, but not quite all, sunburn-producing UVB (280–315 nm). The band of UV closest to visible light, UVA (315–400 nm), is hardly affected by ozone, and most of it reaches the ground.
Ozone cracking in natural rubber tubing
Red Alder leaf, showing discolouration caused by ozone pollution
Signboard in Gulfton, Houston indicating an ozone watch
Ozone production demonstration, Fixed Nitrogen Research Laboratory, 1926
A homemade ozone generator. Ozone is produced in the corona discharge
A laboratory method for the preparation of ozone by using Siemen's Ozoniser.

It is an allotrope of oxygen that is much less stable than the diatomic allotrope, breaking down in the lower atmosphere to (dioxygen).

A water molecule consists of two hydrogen atoms and one oxygen atom

Water

Inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent ).

Inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent ).

A water molecule consists of two hydrogen atoms and one oxygen atom
The three common states of matter
Phase diagram of water (simplified)
Tetrahedral structure of water
Model of hydrogen bonds (1) between molecules of water
Water cycle
Overview of photosynthesis (green) and respiration (red)
Water fountain
An environmental science program – a student from Iowa State University sampling water
Total water withdrawals for agricultural, industrial and municipal purposes per capita, measured in cubic metres (m³) per year in 2010
A young girl drinking bottled water
Water availability: the fraction of the population using improved water sources by country
Roadside fresh water outlet from glacier, Nubra
Hazard symbol for non-potable water
Water is used for fighting wildfires.
San Andrés island, Colombia
Water can be used to cook foods such as noodles
Sterile water for injection
Band 5 ALMA receiver is an instrument specifically designed to detect water in the universe.
South polar ice cap of Mars during Martian south summer 2000
An estimate of the proportion of people in developing countries with access to potable water 1970–2000
People come to Inda Abba Hadera spring (Inda Sillasie, Ethiopia) to wash in holy water
Icosahedron as a part of Spinoza monument in Amsterdam.
Water requirement per tonne of food product
Irrigation of field crops
Specific heat capacity of water

Its chemical formula, H2O, indicates that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds.

Idealized representation of a molecule of a typical triglyceride, the main type of fat. Note the three fatty acid chains attached to the central glycerol portion of the molecule.

Fat

In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds, most commonly those that occur in living beings or in food.

In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds, most commonly those that occur in living beings or in food.

Idealized representation of a molecule of a typical triglyceride, the main type of fat. Note the three fatty acid chains attached to the central glycerol portion of the molecule.
Composition of fats from various foods, as percentage of their total fat
The obese mouse on the left has large stores of adipose tissue. For comparison, a mouse with a normal amount of adipose tissue is shown on the right.
Amounts of fat types in selected foods
Schematic diagram of a triglyceride with a saturated fatty acid (top), a monounsaturated one (middle) and a polyunsaturated one (bottom).
Margarine, a common product that can contain trans fatty acids
Cover of original Crisco cookbook, 1912. Crisco was made by hydrogenating cottonseed oil. The formula was revised in the 2000s and now has only a small amount of trans fat.
Wilhelm Normann patented the hydrogenation of liquid oils in 1902
Conversion of cis to trans fatty acids in partial hydrogenation
Reference ranges for blood tests, showing usual ranges for triglycerides (increasing with age) in orange at right.

The term may also be used more broadly as a synonym of lipid—any substance of biological relevance, composed of carbon, hydrogen, or oxygen, that is insoluble in water but soluble in non-polar solvents.

Priestley by Ellen Sharples (1794)

Joseph Priestley

English chemist, natural philosopher, separatist theologian, grammarian, multi-subject educator, and liberal political theorist who published over 150 works.

English chemist, natural philosopher, separatist theologian, grammarian, multi-subject educator, and liberal political theorist who published over 150 works.

Priestley by Ellen Sharples (1794)
Priestley's birthplace (since demolished) in Fieldhead, Birstall, West Yorkshire – about six miles (10 km) southwest of Leeds
Title page of Rudiments of English Grammar (1761)
Mary Priestley, by Carl F. von Breda (1793); daughter of ironmaster Isaac Wilkinson, sister of industrialist John Wilkinson
A redacted version of A New Chart of History (1765); Priestley believed this chart would "impress" upon students "a just image of the rise, progress, extent, duration, and contemporary state of all the considerable empires that have ever existed in the world"
Priestley's "electrical machine for amateur experimentalists", illustrated in the first edition of his Familiar Introduction to the Study of Electricity (1768)
The earliest known portrait of Priestley, known as the "Leeds" portrait (c. 1763); except for his membership on the Leeds Library Committee, Priestley was not active in the town's social life
Priestley had been working on Institutes of Natural and Revealed Religion since his Daventry days.
His Essay on the First Principles of Government (1768) influenced early 19th-century political philosophers, including Jeremy Bentham.
Optics: The History and Present State of Vision, Light, and Colours, published in 1772, London
A portrait of Priestley commissioned by his publisher and close friend Joseph Johnson from Henry Fuseli (c. 1783)
By 1782, at least a dozen hostile refutations were published to Disquisitions relating to Matter and Spirit, and Priestley was branded an atheist.
Equipment used by Priestley in his experiments on gases, 1775
The laboratory at Lord Shelburne's estate, Bowood House in Wiltshire, in which Priestley discovered oxygen
William Petty-Fitzmaurice, 1st Marquess of Landsdowne – a fellow Unitarian – built a laboratory for the famous dissenter at Bowood House.
One of a set of Lunar Society Moonstones commemorating Priestley at Great Barr, Birmingham
Antoine Lavoisier and his wife, Marie-Anne Pierrette Paulze, by Jacques-Louis David, 1788
DOCTOR PHLOGISTON, The PRIESTLEY politician or the Political Priest: An anti-Priestley cartoon shows him trampling on the Bible and burning documents representing English freedom. "Essays on Matter and Spirit", "Gunpowder", and "Revolution Toasts" bulge from his pockets.
"A Word of Comfort" by William Dent (dated 22 March 1790). Priestley is preaching in front of Charles James Fox who asks "Pray, Doctor, is there such a thing as a Devil?", to which Priestley responds "No" while the devil prepares to attack Priestley from behind.
The attack on Priestley's home, Fairhill, Sparkbrook, Birmingham
The Priestleys' rural Pennsylvania home never became the centre of a utopian community, as the expected emigrants could not afford the journey.
Priestley, painted late in life by Rembrandt Peale (c. 1800); Americans knew Priestley less as a man of science and more as a defender of the freedom of the colonies and of Dissenters.
Priestley's original 1804 gravestone in Riverview Cemetery, Northumberland, Pennsylvania. Visible at right is part of the new stone, placed in front of it in 1971.
A blue plaque from the Royal Society of Chemistry commemorates Priestley at New Meeting Street, Birmingham
Reproduction of Joseph Priestley's oxygen apparatus

Priestley is credited with his independent discovery of oxygen by the thermal decomposition of mercuric oxide, having isolated it in 1774.