Cheat Engine

[Prince charming]

What's 2 + 2.

[Willy]

Oxygen.

[Jake!]

Feces?

[redslothx]

its an equation with no apparent product.


it is simple the numbers 2, the sign Plus, and the number 2 again.

[Prince charming]

[AndrewMan]

/ddd\\\\\\\\+++5n

[Willy]

[redslothx]

4


or


2+2 = 2+2

or

pie fatty pie

[Prince charming]

[AndrewMan]

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]

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.

Oxygen was independently discovered by Joseph Priestley in Wiltshire, in 1774, and Carl Wilhelm Scheele, in Uppsala, a year earlier, but Priestley is often 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.
Contents
[hide]

* 1 Characteristics
o 1.1 Structure
o 1.2 Allotropes
o 1.3 Physical properties
o 1.4 Isotopes and stellar origin
o 1.5 Occurrence
* 2 Biological role
o 2.1 Photosynthesis and respiration
o 2.2 Build-up in the atmosphere
* 3 History
o 3.1 Early experiments
o 3.2 Phlogiston theory
o 3.3 Discovery
o 3.4 Lavoisier's contribution
o 3.5 Later history
* 4 Industrial production
* 5 Applications
o 5.1 Medical
o 5.2 Life support and recreational use
o 5.3 Industrial
o 5.4 Scientific
* 6 Compounds
o 6.1 Oxides and other inorganic compounds
o 6.2 Organic compounds and biomolecules
* 7 Precautions
o 7.1 Toxicity
o 7.2 Combustion and other hazards
* 8 See also
* 9 Notes and citations
* 10 References
* 11 External links

Characteristics

Structure
Electron shell diagram of oxygen
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 simplified in description as a double bond[6] or as a combination of one two-electron bond and two three-electron bonds.[7]

Triplet oxygen is the ground state of the O2 molecule.[8] The electron configuration of the molecule has two unpaired electrons occupying two degenerate molecular orbitals.[9] 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.[8]

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.[10] 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.[11][12]

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.[13] It is also produced in the troposphere by the photolysis of ozone by light of short wavelength,[14] and by the immune system as a source of active oxygen.[15] 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.[16]

Allotropes

Main article: Allotropes of oxygen

Ozone is a rare gas on Earth found mostly in the stratosphere.
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.[17] 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.

Trioxygen (O3) is usually known as ozone and is a very reactive allotrope of oxygen that is damaging to lung tissue.[18] 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.[19]

The metastable molecule tetraoxygen (O4) was discovered in 2001,[20][21] 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.[22] 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.[20][21] A metallic phase was discovered in 1990 when solid oxygen is subjected to a pressure of above 96 GPa[23] and it was shown in 1998 that at very low temperatures, this phase becomes superconducting.[24]

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).[25][26] 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.[27] 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.

Oxygen condenses at 90.20 K (−182.95 °C, −297.31 °F), and freezes at 54.36 K (−218.79 °C, −361.82 °F).[28] 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;[29] 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.[30]

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.
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).[31] Oxygen isotopes range in mass number from 12 to 28.[31]

Most 16O is synthesized at the end of the helium fusion process in stars but some is made in the neon burning process.[32] 17O 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.[32] 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.[32]

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.[31] 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.[31] 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.[31]

Occurrence

See also: Silicate minerals and Category:Oxide minerals

Oxygen is the most abundant chemical element, by mass, in our biosphere, air, sea and land. 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] Oxygen gas 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).[33][3][34] 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.
Cold water holds more dissolved O2.
Cold water holds more dissolved O2.

The unusually high concentration of oxygen gas 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. Photosynthesis releases oxygen into the atmosphere, while respiration and decay remove it from the atmosphere. In the present equilibrium, production and consumption occur at the same rate of roughly 1/2000th of the entire atmospheric oxygen per year.

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.[35] 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.[36]

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.
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.[37]

A simplified overall formula for photosynthesis is:[38]

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.[39] 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.[40] The O2 remaining after oxidation of the water molecule is released into the atmosphere.[41]

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:

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.[42][18] Other animals use hemocyanin (molluscs and some arthropods) or hemerythrin (spiders and lobsters).[33] A liter of blood can dissolve 200 cc of O2.[33]

Reactive oxygen species, such as superoxide ion (O2−) and hydrogen peroxide (H2O2), are dangerous by-products of oxygen use in organisms.[33] 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.[40]

An adult human in rest inhales 1.8 to 2.4 grams of oxygen per minute.[43] This amounts to more than 6 billion tonnes of oxygen inhaled by humanity per year. [44]

Build-up in the atmosphere
O2 build-up in Earth's atmosphere: 1) no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates
O2 build-up in Earth's atmosphere: 1) no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates

Free oxygen gas was almost nonexistent in Earth's atmosphere before photosynthetic archaea and bacteria evolved. Free oxygen first appeared in significant quantities during the Paleoproterozoic era (between 2.5 and 1.6 billion years ago). At first, the oxygen combined with dissolved iron in the oceans to form banded iron formations. Free oxygen started to gas out of the oceans 2.7 billion years ago, reaching 10% of its present level around 1.7 billion years ago.[45]

The presence of large amounts of dissolved and free oxygen in the oceans and atmosphere may have driven most of the anaerobic organisms then living to extinction during the oxygen catastrophe about 2.4 billion years ago. However, cellular respiration using O2 enables aerobic organisms to produce much more ATP than anaerobic organisms, helping the former to dominate Earth's biosphere.[46] Photosynthesis and cellular respiration of O2 allowed for the evolution of eukaryotic cells and ultimately complex multicellular organisms such as plants and animals.

Since the beginning of the Cambrian era 540 million years ago, O2 levels have fluctuated between 15% and 30% per volume.[47] Towards the end of the Carboniferous era (about 300 million years ago) atmospheric O2 levels reached a maximum of 35% by volume,[47] allowing insects and amphibians to grow much larger than today's species. Human activities, including the burning of 7 billion tonnes of fossil fuels each year have had very little effect on the amount of free oxygen in the atmosphere.[10] At the current rate of photosynthesis it would take about 2,000 years to regenerate the entire O2 in the present atmosphere.[48]

History

Early experiments
Philo's experiment inspired later investigators.
Philo's experiment inspired later investigators.

One of the first known experiments on the relationship between combustion and air was conducted by the second century BCE Greek writer on mechanics, Philo of Byzantium. In his work Pneumatica, Philo observed that inverting a vessel over a burning candle and surrounding the vessel's neck with water resulted in some water rising into the neck.[49] Philo incorrectly surmised that parts of the air in the vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries later Leonardo da Vinci built on Philo's work by observing that a portion of air is consumed during combustion and respiration.[50]

In the late 17th century, Robert Boyle proved that air is necessary for combustion. English chemist John Mayow refined this work by showing that fire requires only a part of air that he called spiritus nitroaereus or just nitroaereus.[51] In one experiment he found that placing either a mouse or a lit candle in a closed container over water caused the water to rise and replace one-fourteenth of the air's volume before extinguishing the subjects.[52] From this he surmised that nitroaereus is consumed in both respiration and combustion.

Mayow observed that antimony increased in weight when heated, and inferred that the nitroaereus must have combined with it.[51] He also thought that the lungs separate nitroaereus from air and pass it into the blood and that animal heat and muscle movement result from the reaction of nitroaereus with certain substances in the body.[51] Accounts of these and other experiments and ideas were published in 1668 in his work Tractatus duo in the tract "De respiratione".[52]

[Jake!]

You sure it's not feces?

[HackOtaku]

Exactly.

[Restricted]

[redslothx]

paint

[Willy]