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Oxygen is a chemical element; it has symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. Oxygen is the most abundant element in Earth's crust, and after hydrogen and helium, it ...
O. have also been characterized, all short-lived. The longest-lived radioisotope is 15. O. with a half-life of 122.266 (43) s, while the shortest-lived isotope is the unbound 11. O. with a half-life of 198 (12) yoctoseconds, though half-lives have not been measured for the unbound heavy isotopes 27. O. and 28.
These filaments have many functions and are involved in ion and water transfer as well as oxygen, carbon dioxide, acid and ammonia exchange. [4] Each filament contains a capillary network that provides a large surface area for the exchange of gases and ions. Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it ...
Kleiber's plot comparing body size to metabolic rate for a variety of species. [1] Kleiber's law, named after Max Kleiber for his biology work in the early 1930s, is the observation that, for the vast majority of animals, an animal's metabolic rate scales to the 3⁄4 power of the animal's mass. [2] More recently, Kleiber's law has also been ...
Stages 4 and 5 (0.85 Ga–present): O 2 sinks filled, the gas accumulates. [1] Before photosynthesis evolved, Earth's atmosphere had no free diatomic oxygen (O 2). [2] Small quantities of oxygen were released by geological [3] and biological processes, but did not build up in the atmosphere due to reactions with reducing minerals.
Oxygen compounds. Water (H 2 O) is the most familiar oxygen compound. The oxidation state of oxygen is −2 in almost all known compounds of oxygen. The oxidation state −1 is found in a few compounds such as peroxides. Compounds containing oxygen in other oxidation states are very uncommon: − 1⁄2 (superoxides), − 1⁄3 (ozonides), 0 ...
This reflects the fact that, at extremely high temperatures and pressures, the liquid and gaseous phases become indistinguishable, [3] in what is known as a supercritical fluid. In water, the critical point occurs at around T c = 647.096 K (373.946 °C), p c = 22.064 MPa (217.75 atm) and ρ c = 356 kg/m 3. [4]
Infobox references. Singlet oxygen, systematically named dioxygen (singlet) and dioxidene, is a gaseous inorganic chemical with the formula O=O (also written as 1. [O. 2] or 1. O. 2), which is in a quantum state where all electrons are spin paired. It is kinetically unstable at ambient temperature, but the rate of decay is slow.