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Oxygen is a chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table , a highly reactive nonmetal , and a potent oxidizing agent that readily forms oxides with most elements as well as with other compounds .
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 ...
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 from the Latin alphabet and are written with the first letter capitalised.
Oxygen is the chemical element with atomic number 8, occurring mostly as 16 O, but also 17 O and 18 O. Oxygen is the third-most common element by mass in the universe (although there are more carbon atoms, each carbon atom is lighter). It is highly electronegative and non-metallic, usually diatomic, gas down to very low temperatures.
Even though oxygen is a chalcogen, its chemical properties are different from those of other chalcogens. One reason for this is that the heavier chalcogens have vacant d-orbitals. Oxygen's electronegativity is also much higher than those of the other chalcogens.
Oxygen-18 (18 O, Ω [1]) is a natural, stable isotope of oxygen and one of the environmental isotopes.. 18 O is an important precursor for the production of fluorodeoxyglucose (FDG) used in positron emission tomography (PET).
Oxygen-16 (symbol: 16 O or 16 8 O) is a nuclide. It is a stable isotope of oxygen, with 8 neutrons and 8 protons in its nucleus, and when not ionized, 8 electrons orbiting the nucleus. Oxygen-16 has a mass of 15.994 914 619 56 u. It is the most abundant isotope of oxygen and accounts for 99.757% of oxygen's natural abundance. [2]
Atomic oxygen, denoted O or O 1, is very reactive, as the individual atoms of oxygen tend to quickly bond with nearby molecules. Its lowest-energy electronic state is a spin triplet, designated by the term symbol 3 P. On Earth's surface, it exists naturally for a very short time.