There are three known stable

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numb ...

s of

oxygen Oxygen is the 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 an oxidizing agent that readily forms oxides with most elements as ...

(₈O): , , and .

Radioactive isotopes A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...

ranging from to have also been characterized, all short-lived. The longest-lived radioisotope is with a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...

of , while the shortest-lived isotope is with a half-life of (though the half-lives of the neutron-unbound and are still unknown).

List of isotopes

, - , , style="text-align:right" , 8 , style="text-align:right" , 3 , ,
[] , proton emission, 2p , , (3/2−) , , , - , , style="text-align:right" , 8 , style="text-align:right" , 4 , , , 2p , , 0+ , , , - , rowspan=2, , rowspan=2 style="text-align:right" , 8 , rowspan=2 style="text-align:right" , 5 , rowspan=2, , rowspan=2, , β⁺ () , , rowspan=2, (3/2−) , rowspan=2, , rowspan=2, , - , β⁺p () , , - , , style="text-align:right" , 8 , style="text-align:right" , 6 , , , β⁺ , , 0+ , , , - , , style="text-align:right" , 8 , style="text-align:right" , 7 , , , β⁺ , , 1/2− , , , - , The ratio between and is used to deduce ancient temperatures. , style="text-align:right" , 8 , style="text-align:right" , 8 , , colspan="3" style="text-align:center;", Stable , 0+ , colspan="2" style="text-align:center;", ref name="Atomic Weight of Oxygen"> , - , Can be used in NMR studies of metabolic pathways. , style="text-align:right" , 8 , style="text-align:right" , 9 , , colspan="3" style="text-align:center;", Stable , 5/2+ , colspan="2" style="text-align:center;", ref name="Atomic Weight of Oxygen" /> , - , Can be used in studying certain metabolic pathways. , style="text-align:right" , 8 , style="text-align:right" , 10 , , colspan="3" style="text-align:center;", Stable , 0+ , colspan="2" style="text-align:center;", ref name="Atomic Weight of Oxygen" /> , - , , style="text-align:right" , 8 , style="text-align:right" , 11 , , , β⁻ , , 5/2+ , , , - , , style="text-align:right" , 8 , style="text-align:right" , 12 , , , β⁻ , , 0+ , , , - , rowspan=2, , rowspan=2 style="text-align:right" , 8 , rowspan=2 style="text-align:right" , 13 , rowspan=2, , rowspan=2, , β⁻ , , rowspan=2, (5/2+) , rowspan=2, , rowspan=2, , - , β⁻n ?Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide. , ? , - , rowspan=2, , rowspan=2 style="text-align:right" , 8 , rowspan=2 style="text-align:right" , 14 , rowspan=2, , rowspan=2, , β⁻ (> ) , , rowspan=2, 0+ , rowspan=2, , rowspan=2, , - , β⁻n (< ) , , - , rowspan=2, , rowspan=2 style="text-align:right" , 8 , rowspan=2 style="text-align:right" , 15 , rowspan=2, , rowspan=2, , β⁻ () , , rowspan=2, 1/2+ , rowspan=2, , rowspan=2, , - , β⁻n () , , - , rowspan=2, , rowspan=2 style="text-align:right" , 8 , rowspan=2 style="text-align:right" , 16 , rowspan=2, , rowspan=2, , β⁻ () , , rowspan=2, 0+ , rowspan=2, , rowspan=2, , - , β⁻n () , , - , , style="text-align:right" , 8 , style="text-align:right" , 17 , , , n , , 3/2+ , , , - , , style="text-align:right" , 8 , style="text-align:right" , 18 , , , 2n , , 0+ , , , - , rowspan=2, ?This isotope has not yet been observed; given data is inferred or estimated from periodic trends. , rowspan=2 style="text-align:right" , 8 , rowspan=2 style="text-align:right" , 19 , rowspan=2, , rowspan=2, < , n ?Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide. , ? , rowspan=2, 3/2+ , rowspan=2, , rowspan=2, , - , 2n ?Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide. , ? , - , rowspan=2, ? , rowspan=2 style="text-align:right" , 8 , rowspan=2 style="text-align:right" , 20 , rowspan=2, , rowspan=2, < , 2n ?Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide. , ? , rowspan=2, 0+ , rowspan=2, , rowspan=2, , - , β⁻ () ,

Stable isotopes

Natural oxygen is made of three stable

s, , , and , with being the most abundant (99.762%

natural abundance In physics, natural abundance (NA) refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass (a weighted average, weighted by mole-fraction abundance figures) of these isotopes is the atomi ...

). Depending on the terrestrial source, the standard atomic weight varies within the range of (the conventional value is 15.999). has high relative and absolute abundance because it is a principal product of stellar evolution and because it is a primary isotope, meaning it can be made by stars that were initially

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

only. Most is synthesized at the end of the

helium fusion The triple-alpha process is a set of nuclear fusion reactions by which three helium-4 nuclei (alpha particles) are transformed into carbon. Triple-alpha process in stars Helium accumulates in the cores of stars as a result of the proton–pro ...

process in stars; the

triple-alpha process The triple-alpha process is a set of nuclear fusion reactions by which three helium-4 nuclei (alpha particles) are transformed into carbon. Triple-alpha process in stars Helium accumulates in the cores of stars as a result of the proton–pro ...

creates , which captures an additional nucleus to produce . The

neon burning process The neon-burning process is a set of nuclear fusion reactions that take place in evolved massive stars with at least 8 Solar masses. Neon burning requires high temperatures and densities (around 1.2×109 K or 100 keV and 4×109 kg/m3). At such h ...

creates additional . Both and are secondary isotopes, meaning their synthesis requires seed nuclei. is primarily made by burning hydrogen into helium in the

CNO cycle The CNO cycle (for carbon–nitrogen–oxygen; sometimes called Bethe–Weizsäcker cycle after Hans Albrecht Bethe and Carl Friedrich von Weizsäcker) is one of the two known sets of fusion reactions by which stars convert hydrogen to helium, ...

, making it a common isotope in the hydrogen burning zones of stars. Most is produced when (made abundant from CNO burning) captures a nucleus, becoming . This quickly (half life around 110 minutes)

beta decay In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...

s to making that isotope common in the helium-rich zones of stars. About 10⁹

kelvin The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and phy ...

is needed to fuse oxygen into sulfur. An atomic mass of 16 was assigned to oxygen prior to the definition of the unified

atomic mass unit The dalton or unified atomic mass unit (symbols: Da or u) is a non-SI unit of mass widely used in physics and chemistry. It is defined as of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at ...

based on . Since physicists referred to only, while chemists meant the natural mix of isotopes, this led to slightly different mass scales.

Applications of various isotopes

Measurements of ¹⁸O/¹⁶O ratio are often used to interpret changes in paleoclimate. Oxygen in Earth's air is , and .

Water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...

molecules with a lighter isotope are slightly more likely to evaporate and less likely to fall as

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...

, so Earth's freshwater and polar ice have slightly less () than air () or

seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appr ...

(). This disparity allows analysis of temperature patterns via historic ice cores. Solid samples (organic and inorganic) for oxygen isotopic ratios are usually stored in silver cups and measured with

pyrolysis The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements ''py ...

and mass spectrometry. Researchers need to avoid improper or prolonged storage of the samples for accurate measurements. Due to natural oxygen being mostly samples enriched with the other stable isotopes can be used for

isotope labeling Isotopic labeling (or isotopic labelling) is a technique used to track the passage of an isotope (an atom with a detectable variation in neutron count) through a reaction, metabolic pathway, or cell. The reactant is 'labeled' by replacing specific ...

. For example, it was proven, that the oxygen released in

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

originates in , rather than in the also consumed , by isotope tracing experiments. The oxygen contained in in turn is used to make up the sugars formed by photosynthesis. In

heavy water reactor A pressurized heavy-water reactor (PHWR) is a nuclear reactor that uses heavy water ( deuterium oxide D2O) as its coolant and neutron moderator. PHWRs frequently use natural uranium as fuel, but sometimes also use very low enriched uranium. The ...

s the neutron moderator should preferably be low in and due to their higher neutron absorption cross section compared to . While this effect can also be observed in

light water reactor The light-water reactor (LWR) is a type of thermal-neutron reactor that uses normal water, as opposed to heavy water, as both its coolant and neutron moderator; furthermore a solid form of fissile elements is used as fuel. Thermal-neutron react ...

s, ordinary hydrogen ( protium) has a higher absorption cross section than any stable isotope of oxygen and its number density is twice as high in water as that of oxygen so that the effect is negligible. As some methods of

isotope separation Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes. The use of the nuclides produced is varied. The largest variety is used in research (e.g. in chemistry where atoms of "marker" n ...

enrich not only heavier isotopes of hydrogen but also heavier isotopes of oxygen when producing heavy water, the concentration of and can be measurably higher. Furthermore the (n,α) reaction is a further undesirable result of an elevated concentration of heavier isotopes of oxygen. Therefore facilities which remove

tritium Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with half-life about 12 years. The nucleus of tritium (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus of ...

from heavy water used in nuclear reactors often also remove or at least reduce the amount of heavier isotopes of oxygen. Oxygen isotopes are also used to trace ocean composition and temperature which seafood is from.

Radioisotopes

Thirteen

radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...

s have been characterized; the most stable are with

and with half-life . All remaining radioisotopes have half-lives less than and most have half-lives less than 0.1 s. has half-life . The most common decay mode for isotopes lighter than the stable isotopes is β⁺ decay to

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

, and the most common mode after is β⁻ decay to fluorine.

Oxygen-13

Oxygen-13 is an unstable

, with 8 protons and 5 neutrons. It has spin 3/2−, and

. Its atomic mass is . It decays to

nitrogen-13 Nitrogen-13 (13N) is a radioisotope of nitrogen used in positron emission tomography (PET). It has a half-life of a little under ten minutes, so it must be made at the PET site. A cyclotron may be used for this purpose. Nitrogen-13 is used to tag ...

by electron capture, with a decay energy of . Its parent nuclide is fluorine-14.

Oxygen-15

Oxygen-15 is a radioisotope, often used in positron emission tomography (PET). It can be used in, among other things,

water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...

for PET

myocardial perfusion imaging Myocardial perfusion imaging or scanning (also referred to as MPI or MPS) is a nuclear medicine procedure that illustrates the function of the heart muscle ( myocardium). It evaluates many heart conditions, such as coronary artery disease (CAD), ...

and for

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a ve ...

imaging. It has an atomic mass of , and a

of . It is produced through

deuteron Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two stable isotopes of hydrogen (the other being protium, or hydrogen-1). The nucleus of a deuterium atom, called a deuteron, contains one proton and one n ...

bombardment of

nitrogen-14 Natural nitrogen (7N) consists of two stable isotopes: the vast majority (99.6%) of naturally occurring nitrogen is nitrogen-14, with the remainder being nitrogen-15. Fourteen radioisotopes are also known, with atomic masses ranging from 10 to 25, ...

using a

cyclotron A cyclotron is a type of particle accelerator invented by Ernest O. Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: Jan ...

. Oxygen-15 and nitrogen-13 are produced in air when

gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...

s (for example from

lightning Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions, both in the atmosphere or with one on the ground, temporarily neutralize themselves, causing the instantaneous release of an avera ...

) knock neutrons out of ¹⁶O and ¹⁴N: : + γ → + n : + γ → + n decays to , emitting a positron. The positron quickly annihilates with an electron, producing two gamma rays of about 511 keV. After a lightning bolt, this gamma radiation dies down with half-life 2 min, but these low-energy gamma rays go on average only about 90 metres through the air. Together with rays produced from positrons from nitrogen-13 they may only be detected for a minute or so as the "cloud" of and floats by, carried by the wind.

References

* * * {{Authority control Oxygen

Oxygen Oxygen is the 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 an oxidizing agent that readily forms oxides with most elements as ...