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Oxygen

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Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table and is a highly reactive nonmetallic element and oxidizing agent that readily forms compounds (notably oxides) with most elements.

Photosynthesis releases oxygen, and respiration consumes oxygen. Changes in phosphate are related to changes in oxygen concentrations.

Oxygen was discovered independently by Carl Wilhelm Scheele, in Uppsala, in 1773 or earlier, and Joseph Priestley in Wiltshire, in 1774, but Priestley is often given priority because his work was published first. The name oxygen was coined in 1777 by Antoine Lavoisier, whose experiments with oxygen helped to discredit the then-popular phlogiston theory of combustion and corrosion. Its name derives from the Greek roots ὀξύς oxys, "acid", literally "sharp", referring to the sour taste of acids and -γενής -genes, "producer", literally "begetter", because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition.

Geological history of oxygen. O2 build-up in the Earth's atmosphere.

Geological history of oxygen

Red and green lines represent the range of the estimates while time is measured in billions of years ago (Ga). Stage 1 (3.85–2.45 Ga): Practically no O2 in the atmosphere. Stage 2 (2.45–1.85 Ga): O2 produced, but absorbed in oceans & seabed rock. Stage 3 (1.85–0.85 Ga): O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer. Stages 4 & 5 (0.85 Ga–present): O2 sinks filled, the gas accumulates.[1] Before photosynthesis evolved, Earth's atmosphere had no free oxygen (O2).[2] Photosynthetic prokaryotic organisms that produced O2 as a waste product lived long before the first build-up of free oxygen in the atmosphere,[3] perhaps as early as 3.5 billion years ago.

Effects on life[edit] Oxygen. Oxygen was discovered independently by Carl Wilhelm Scheele, in Uppsala, in 1773 or earlier, and Joseph Priestley in Wiltshire, in 1774, but Priestley is often given priority because his work was published first.

Oxygen

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. Its name derives from the Greek roots ὀξύς oxys, "acid", literally "sharp", referring to the sour taste of acids and -γενής -genes, "producer", literally "begetter", because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition.

Characteristics By mass, oxygen is the third-most abundant element in the universe, after hydrogen and helium.[6] At standardized conditions for temperature and pressure, two atoms of the element bind to form dioxygen, a diatomic gas that is colorless, odorless, and tasteless, with the formula O 2. [citation needed] Allotropes Occurrence.

Characteristics

Biological role of O2. History. Industrial production. Storage. Applications. Compounds. Safety and precautions. Limiting oxygen concentration. Flammability diagram, green dotted line shows safe purging of an air-filled vessel, first with nitrogen, then with methane, to avoid the flammable region.

Limiting oxygen concentration

Hypoxia (medical) Hypoxia (also known as Hypoxiation or Anoxemia) is a condition in which the body or a region of the body is deprived of adequate oxygen supply.

Hypoxia (medical)

Hypoxia may be classified as either generalized, affecting the whole body, or local, affecting a region of the body. Although hypoxia is often a pathological condition, variations in arterial oxygen concentrations can be part of the normal physiology, for example, during hypoventilation training[1] or strenuous physical exercise. Hypoxia differs from hypoxemia in that hypoxia refers to a state in which oxygen supply is insufficient, whereas hypoxemia refers specifically to states that have low arterial oxygen supply.[2] Hypoxia in which there is complete deprivation of oxygen supply is referred to as "anoxia". Hypoxia is also a serious consequence of preterm birth in the neonate. The main cause for this is that the lungs of the human fetus are among the last organs to develop during pregnancy. Extreme pain may also be felt at or around the site. Ocean deoxygenation.

Ocean deoxygenation is a term that has been suggested to describe the expansion of oxygen minimum zones in the world's oceans as a consequence of anthropogenic emissions of carbon dioxide [1][2].

Ocean deoxygenation

Implications[edit] Ocean deoxygenation poses implications for ocean productivity, nutrient cycling, carbon cycling, and marine habitat. Ocean model simulations predict a decline of up to 7% in the global ocean O2 content over the next hundred years. Hypoxia (environmental) Hypoxia refers to low oxygen conditions.

Hypoxia (environmental)

Normally 20.9% of the gas in the atmosphere is oxygen. The partial pressure of oxygen in the atmosphere is 20.9% of the total barometric pressure.[1] In water however, oxygen levels are much lower, approximately 1%, and fluctuate locally depending on the presence of photosynthetic organisms and relative distance to the surface (there is more oxygen in the air, which will diffuse across the partial pressure gradient).[2] Atmospheric hypoxia occurs naturally at high altitudes.

Total atmospheric pressure decreases as altitude increases, causing a lower partial pressure of oxygen which is defined as hypobaric hypoxia. Geological history of oxygen.