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Oxygen is the third most abundant chemical element in the universe, after hydrogen and helium.[67] About 0.9% of the Sun's mass is oxygen.[18] Oxygen constitutes 49.2% of the Earth's crustby mass[68]as part of oxide compounds such as silicon dioxideand is the most abundant element by mass in the Earth's crust.
Geological history of oxygen. O 2 build-up in the Earth's atmosphere. 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 O 2 in the atmosphere. Stage 2 (2.45–1.85 Ga): O 2 produced, but absorbed in oceans and seabed rock.
The oxygen cycle is the biogeochemical cycle of oxygen atoms between different oxidation states in ions, oxides, and molecules through redox reactions within and between the spheres/reservoirs of the planet Earth. [1] The word oxygen in the literature typically refers to the most common oxygen allotrope, elemental/diatomic oxygen (O 2), as it ...
There are three known stable isotopes of oxygen (8 O): 16O, 17O, and 18O. Radioactive isotopes ranging from 11O to 28O have also been characterized, all short-lived. The longest-lived radioisotope is 15O with a half-life of 122.266 (43) s, while the shortest-lived isotope is the unbound 11O with a half-life of 198 (12) yoctoseconds, though half ...
There are several known allotropes of oxygen. The most familiar is molecular oxygen (O2), present at significant levels in Earth's atmosphere and also known as dioxygen or triplet oxygen. Another is the highly reactive ozone (O3). Others are: Atomic oxygen (O1), a free radical. Singlet oxygen (O*2), one of two metastable states of molecular oxygen.
In aquaticenvironments, oxygen saturation is a ratio of the concentration of "dissolved oxygen" (DO, O2), to the maximum amount of oxygen that will dissolve in that water body, at the temperature and pressure which constitute stable equilibrium conditions. Well-aerated water (such as a fast-moving stream) without oxygen producers or consumers ...
Stages 4 and 5 (0.85 Ga – present): Other O 2 reservoirs filled; gas accumulates in atmosphere. [1] The Great Oxidation Event (GOE) or Great Oxygenation Event, also called the Oxygen Catastrophe, Oxygen Revolution, Oxygen Crisis or Oxygen Holocaust, [2] was a time interval during the Earth 's Paleoproterozoic era when the Earth's atmosphere ...
Oxygen concentrator. An oxygen concentrator is a device that concentrates the oxygen from a gas supply (typically ambient air) by selectively removing nitrogen to supply an oxygen-enriched product gas stream. They are used industrially, to provide supplemental oxygen at high altitudes, and as medical devices for oxygen therapy.