Lavoisier renamed "vital air" to "oxygène", from Greek words meaning "sour making" or "producer of acid". He called it this because he thought oxygen was in all acids, which is wrong. Later chemists realised that Lavoiser's name for the gas was wrong, but the name was too common by then to change.
"Oxygen" became the name in the English language, even though English scientists were against it.
John Dalton's theory of atoms said that all elements had one atom and atoms in compounds were usually alone. For example, he wrongly thought that water (HO) had the formula of just HO. In 1805, Joseph Louis Gay-Lussac and Alexander von Humboldt showed that water is made up of two hydrogen atoms and one oxygen atom. By 1811, Amedeo Avogadro correctly worked out what water was made of based on Avogadro's law.
By the late 19th century, scientists found that air could be turned into a liquid and the compounds in it could be isolated by compressing and cooling it. Swiss chemist and physicist Raoul Pictet discovered liquid oxygen by evaporating sulfur dioxide to turn carbon dioxide into a liquid. This was then also evaporated to cool oxygen gas in order to turn it into a liquid. He sent a telegram to the French Academy of Sciences on 22 December 1877 telling them of his discovery.
At standard temperature and pressure, oxygen has no colour, odour or taste. It is a gas with the chemical formula called dioxygen.
As "dioxygen" (or just "oxygen gas"), two oxygen atoms are chemically bound to each other. This bond can be called many things, but simply called a covalent double bond. Oxygen gas is very reactive and can react with many other elements. Oxides are made when metal elements react with oxygen, such as iron oxide, which is known as rust. There are a lot of oxide compounds on Earth.
The common allotrope (type) of oxygen on Earth is called dioxygen (O). This is the second biggest part of the Earth's atmosphere, after dinitrogen (N). O has a bond length of 121 pm and a bond energy of 498 kJ/mol Because of its energy, O is used by complex life like animals.
Ozone (O) is very reactive and damages the lungs when breathed in. Ozone is made in the upper atmosphere when O combines with pure oxygen made when O is split by ultraviolet radiation. Ozone absorbs a lot of radiation in the UV part of the electromagnetic spectrum and so the ozone layer in the upper atmosphere protects Earth from radiation.
Above the ozone layer, (in low Earth orbits), atomic oxygen becomes the most common form.
Tetraoxygen (O) was discovered in 2001. It only exists in extreme conditions when a lot of pressure is put onto O.
Oxygen dissolves more easily from air into water than nitrogen does. When there is the same amount of air and water, there is one molecule of O for every 2 molecules of N (a ratio of 1:2). This is different to air, where there is a 1:4 ratio of oxygen to nitrogen. It is also easier for O to dissolve in freshwater than in seawater. Oxygen condenses at 90.20 K (-182.95°C, -297.31 °F) and freezes at 54.36 K (-218.79 °C, -361.82 °F). Both liquid and solid O are see-through with a light-blue colour.
Oxygen is very reactive and must be kept away from anything that can burn.
There are three stable isotopes of oxygen in nature. They are O, O, and O. About 99.7% of oxygen is the O isotope.
Oxygen is the third most common element in the universe, after hydrogen and helium. About 0.9% of the Sun's mass is oxygen.
Apart from iron, oxygen is the most common element on Earth (by mass). It makes up nearly half (46%
to 49.2% of the Earth's crust as part of oxide compounds like silicon dioxide and other compounds like carbonates. It is also the main part of the Earth's oceans, making up 88.8% by mass. Oxygen gas is the second most common part of the atmosphere, making up 20.95% of its volume and 23.1% of its volume. Earth is strange compared to other planets, as a large amount of its atmosphere is oxygen gas. Mars has only 0.1% by volume, with the other planets having less than that.
The much higher amount of oxygen gas around Earth is because of the oxygen cycle. Photosynthesis takes hydrogen from water using energy from sunlight, which gives off oxygen gas. The hydrogen combines with carbon dioxide to make carbohydrates. Respiration then takes oxygen gas out of the atmosphere and turns it into carbon dioxide and water. This happens at the nearly same rate, so the amount of oxygen gas and carbon dioxide doesn't change much because of it.
O is a very important part of respiration. Because of this, it is used in medicine. It is used to increase the amount of oxygen in a persons blood so more respiration can take place. This can make them become healthy quicker if they are ill. Oxygen therapy is used to treat emphysema, pneumonia, some heart problems, and any disease that makes it harder for a person to take in oxygen.
Low-pressure O is used in space suits, surrounding the body with the gas. Pure oxygen is used but at a much lower pressure. If the pressure were higher, it would be poisonous.
Smelting of iron ore into steel uses about 55% of oxygen made by humans. To do this, O gas is injected into the ore through a lance at high pressure. This removes any sulfur or carbon from the ore that would not be wanted. They are given off as sulfur oxide and carbon dioxide. The temperature can go as high as 1,700 °C because it is an exothermic reaction.
Around 25% of oxygen made by humans is used by chemists. Ethylene is reacted with O to make ethylene oxide. This is then changed to ethylene glycol, which is used to make many products such as antifreeze and polyester (these can then be turned into plastics and fabrics).
The other 20% of oxygen made by humans is used in medicine, metal cutting and welding, rocket fuel, and water treatment.
The oxidation state of oxygen is −2 in nearly every compound it is in. In a few compounds, the oxidation state is −1, such as peroxides. Compounds of oxygen with other oxygen states are very uncommon.
Water () is an oxide of hydrogen. It is the most common oxide on Earth. All known life needs water to live. Water is made of two hydrogen atoms covalent bonded to an oxygen atom (oxygen has a higher electronegativity than hydrogen). (this is the basic principle of covalent bonding)
There are also electrostatic forces (Van de'r Waals forces) between the hydrogen atoms and adjacent molecules' oxygen atoms. These pseudo-bonds bring the atoms around 15% closer to each other than most other simple liquids. This is because Water is a polar molecule (Net asymmetrical distribution of electrons) due to its bent shape, giving it an overall net field direction, mainly due to oxygens 2 non bonding pairs of electrons, pushing the bonding H's further together than the linear arrangement with lower enthalpy (see CO). This property is exploited by microwaves to oscillate polar molecules, especially water. And its responsible for the extra energy needed to disassociate H0.
Because of oxygen's high electronegativity, it makes chemical bonds with almost all other chemical elements. These bonds give oxides (for example iron reacts with oxygen to give iron oxide). Most metal's surfaces are turned into oxides when in air. Iron's surface will turn to rust (iron oxide) when in air for a long time. There are small amounts of carbon dioxide () in the air, and it is turned into carbohydrates during photosynthesis. Living things give it off during respiration.
Many organic compounds have oxygen in them. Some of the classes of organic compounds that have oxygen are alcohols, ethers, ketones, aldehydes, carboxylic acids, esters, and amides. Many organic solvents also have oxygen, such as acetone, methanol, and isopropanol. Oxygen is also found in nearly all biomolecules that are made by living things.
Oxygen also reacts quickly with many organic compounds at, or below, room temperature when autoxidation happens.