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  2. Oxygen - Wikipedia

    en.wikipedia.org/wiki/Oxygen

    Oxygen is the most abundant element in Earth's crust, and the third-most abundant element in the universe after hydrogen and helium. 2. Dioxygen gas currently constitutes 20.95% molar fraction of the Earth's atmosphere, though this has changed considerably over long periods of time in Earth's history.

  3. Oxygen cycle - Wikipedia

    en.wikipedia.org/wiki/Oxygen_cycle

    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 ...

  4. Allotropes of oxygen - Wikipedia

    en.wikipedia.org/wiki/Allotropes_of_oxygen

    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.

  5. Oxygen compounds - Wikipedia

    en.wikipedia.org/wiki/Oxygen_compounds

    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 ...

  6. Gas - Wikipedia

    en.wikipedia.org/wiki/Gas

    Drifting smoke particles indicate the movement of the surrounding gas.. Gas is one of the four fundamental states of matter.The others are solid, liquid, and plasma. [1] A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or compound molecules made from a variety of atoms (e.g. carbon dioxide).

  7. Isotopes of oxygen - Wikipedia

    en.wikipedia.org/wiki/Isotopes_of_oxygen

    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 ...

  8. Carbon–oxygen bond - Wikipedia

    en.wikipedia.org/wiki/Carbon–oxygen_bond

    A carbon–oxygen bond is a polar covalent bond between atoms of carbon and oxygen. [ 1 ][ 2 ][ 3 ]: 16–22 Carbon–oxygen bonds are found in many inorganic compounds such as carbon oxides and oxohalides, carbonates and metal carbonyls, [ 4 ] and in organic compounds such as alcohols, ethers, and carbonyl compounds. [ 5 ]: 32–36 Oxygen has ...

  9. Molecule - Wikipedia

    en.wikipedia.org/wiki/Molecule

    Also carbohydrates, for example, have the same ratio (carbon:hydrogen:oxygen= 1:2:1) (and thus the same empirical formula) but different total numbers of atoms in the molecule. The molecular formula reflects the exact number of atoms that compose the molecule and so characterizes different molecules.