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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.
About 99% of the mass of the human body is made up of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about 0.85% is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium. All 11 are necessary for life. The remaining elements are trace elements, of which more than a dozen are ...
A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
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 ...
M N−1. In chemistry, the molar mass (M) (sometimes called molecular weight or formula weight, but see related quantities for usage) of a chemical compound is defined as the ratio between the mass and the amount of substance (measured in moles) of any sample of the compound. [1] The molar mass is a bulk, not molecular, property of a substance.
Chemical symbol. The periodic table, elements being denoted by their symbols. Chemical symbols are the abbreviations used in chemistry, mainly for chemical elements; but also for functional groups, chemical compounds, and other entities. Element symbols for chemical elements, also known as atomic symbols, normally consist of one or two letters ...
An oxide (/ ˈɒksaɪd /) is a chemical compound containing at least one oxygen atom and one other element [1] in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of –2) of oxygen, an O 2– ion with oxygen in the oxidation state of −2. Most of the Earth's crust consists of oxides.