Oxygen is the most widely occurring element on Earth. Since, it forms compounds with virtually all chemical elements except the noble gases, most terrestrial oxygen is bound with other elements in compounds such as silicates, oxides, and water. Oxygen is also dissolved in rivers, lakes, and oceans. Molecular oxygen occurs almost entirely in the atmosphere. Its name derives from the Greek roots “oxys” ("acid", literally "sharp", referring to the sour taste of acids) and “genes” ("producer", literally "begetter"). At the time of naming, it was mistakenly thought that all acids required oxygen in their composition. Oxygen is a member of the group 16 on the periodic table, and is a highly reactive nonmetallic element that readily forms compounds (notably oxides) with almost all other elements. By mass, oxygen is the third most abundant element in the universe after hydrogen and helium and the most abundant element by mass in the Earth's crust, making up almost half of the crust's mass.
Free oxygen is too chemically reactive to appear on Earth without the photosynthetic action of living organisms, which use the energy of sunlight to produce elemental oxygen from water. Elemental O2 only began to accumulate in the atmosphere after the evolutionary appearance of these organisms, roughly 2.5 billion years ago. Diatomic oxygen gas constitutes 20.8% of the volume of air. 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. Elemental oxygen is produced by cyanobacteria, algae and plants, and is used in cellular respiration for all complex life. Another form 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.
What is the History of Oxygen?
One of the first known experiments on the relationship between combustion and air was conducted by the 2nd century Greek writer on mechanics, Philo of Byzantium. In the late 17th century, Robert Boyle, natural philosopher, chemist proved that air is necessary for combustion. Oxygen was first discovered by Swedish pharmacist, Carl Wilhelm Scheele. In the meantime, on August 1, 1774, an experiment conducted by the British clergyman, Joseph Priestley, focused sunlight on mercuric oxide (HgO) inside a glass tube, which liberated a gas he named "dephlogisticated air". Priestley is often given priority because his work was published first. The name oxygen was coined in 1777 by Antoine Lavoisier, a French nobleman.
In 1805, Joseph Louis Gay-Lussac, a French chemist and Alexander von Humboldt, a German naturalist showed that water is formed of two volumes of hydrogen and one volume of oxygen. Swiss chemist and physicist, Raoul Pierre Pictet, discovered liquid oxygen on December 22, 1877. In 1891 Scottish chemist, James Dewar, was able to produce enough liquid oxygen to study. The first commercially viable process for producing liquid oxygen was independently developed in 1895 by German engineer, Carl von Linde, and British engineer, William Hampson. In 1923 the American scientist, Robert H. Goddard, became the first person to develop a rocket engine; the engine used gasoline for fuel and liquid oxygen as the oxidizer. Goddard successfully flew a small liquid-fueled rocket 56 m at 97 km/h on March 16, 1926 in Auburn, Massachusetts, USA.
What is the structure 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.
Triplet oxygen (not to be confused with ozone, O3) is the ground state (lowest-energy state) of the O2 molecule
In normal triplet form, O2 molecules are paramagnetic. That is, they form a magnet in the presence of a magnetic field.
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.
Singlet oxygen is a name given to several higher-energy species of molecular O2 in which all the electron spins are paired. It is much more reactive towards common organic molecules than is molecular oxygen per second. In nature, singlet oxygen is commonly formed from water during photosynthesis, using the energy of sunlight.
Carotenoids (organic pigments) 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 You do not have access to view this node.
Oxygen is more soluble in water than nitrogen is; 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.
At 25 °C and 1 standard atmosphere (101.3 kPa) of air, freshwater contains about 6.04 milliliters (mL) of oxygen per liter, whereas seawater contains about 4.95 mL per liter.
Oxygen condenses at 90.20 K (−182.95 °C, −297.31 °F). Both liquid and solid O2 are clear substances with a light sky-blue color caused by absorption in the red.
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.
What are the Allotropes (physical forms) of Oxygen?
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. This is the form that is used by complex forms of life, such as animals, in cellular respiration and is the form that is a major part of the Earth's atmosphere.
Trioxygen (O3) is usually known as ozone and is a very reactive allotrope of oxygen that is damaging to lung tissue. Ozone is produced in the upper atmosphere when O2 combines with atomic oxygen made by the splitting of O2 by ultraviolet (UV) radiation. Since ozone absorbs strongly in the UV region of the spectrum, the ozone layer of the upper atmosphere functions as a protective radiation shield for the planet.
The metastable (general scientific concept which describes states of delicate equilibrium) molecule tetraoxygen (O4) was discovered in 2001, and was assumed to exist as “solid oxygen”. Solid oxygen forms at normal atmospheric pressure at a temperature below 54.36 K.
It was proven in 2006 that this phase, created by pressurizing O2 to 20 GPa, is in fact an O8 cluster. 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.
What are the Isotopes of Oxygen?
Naturally occurring oxygen is composed of three stable isotopes, O-16, O-17, and O-18, with O-16 being the most abundant (99.762% natural abundance).
Fourteen radioisotopes have been characterized, the most stable being O-15 with a half-life of 122.24 seconds and O-14 with a half-life of 70.606 seconds.
All of the remaining radioactive isotopes have half-lives that are less than 27 seconds and the majority of these have half-lives that are less than 83 milliseconds.
How is oxygen produced?
The most common method is to fractionally distill liquefied air into its various components, with nitrogen N2 distilling as a vapor while oxygen O2 is left as a liquid. 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.
The other major method of producing O2 gas involves passing a stream of clean, dry air through one bed of a pair of identical zeolite microporous, aluminosilicate minerals commonly used as commercial adsorbents) molecular sieves, which absorbs the nitrogen and delivers a gas stream that is 90% to 93% O2.
What are the Applications of Oxygen?
Medicine: Uptake of O2 from the air is the essential purpose of respiration, so oxygen supplementation is used in medicine. Treatment not only increases oxygen levels in the patient's blood, but has the secondary effect of decreasing resistance to blood flow in many types of diseased lungs, easing work load on the heart. Oxygen therapy is used to treat emphysema (disease of the lungs that primarily causes shortness of breath), pneumonia, some heart disorders (congestive heart failure).
Life support: A notable application of O2 as a low-pressure breathing gas is in modern space suits, which surround their occupant's body with pressurized air. These devices use nearly pure oxygen at about one third normal pressure, resulting in a normal blood partial pressure of O2. Scuba divers and submariners also rely on artificially delivered O2, but most often use normal pressure, and/or mixtures of oxygen and air.
Industrial: 25% of commercially produced oxygen is used by the chemical industry. Smelting of iron ore into steel consumes 55% of commercially produced oxygen.
Rockets: Larger rockets use liquid oxygen as their oxidizer, which is mixed and ignited with the fuel for propulsion.
Scientific purposes: Paleoclimatologists (study of changes in climate)measure the ratio of oxygen-18 and oxygen-16 in the shells and skeletons of marine organisms to determine what the climate was like millions of years ago. Planetary geologists have measured different abundances of oxygen isotopes in samples from the Earth, the Moon, Mars, and meteorites, but were long unable to obtain reference values for the isotope ratios in the Sun.