| General | |
|---|---|
| Symbol | 16O |
| Names | oxygen-16, 16O, O-16 |
| Protons (Z) | 8 |
| Neutrons (N) | 8 |
| Nuclide data | |
| Natural abundance | 99.76% |
| Half-life (t1/2) | stable |
| Isotope mass | 15.99491461956 Da |
| Spin | 0 |
| Excess energy | −4737.00135(16)[1] keV |
| Isotopes of oxygen Complete table of nuclides | |
Oxygen-16 (symbol: 16O or 16
8O
) 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 15.99491461956 u. It is the most abundant isotope of oxygen and accounts for 99.762% of oxygen's natural abundance.[2]
The relative and absolute abundances of oxygen-16 are high because it is a principal product of stellar evolution and because it is a primordial isotope, meaning it can be made by stars that were initially made exclusively of hydrogen.
Most oxygen-16 is synthesized at the end of the helium fusion process in stars; the triple-alpha process creates carbon-12, which captures an additional helium-4 to make oxygen-16. The neon-burning process also makes it.
Oxygen-16 is doubly magic.
Solid samples (organic and inorganic) for oxygen-16 studies are usually stored in silver cups and measured with pyrolysis and mass spectrometry.[3] Researchers need to avoid improper or prolonged storage of the samples for accurate measurements.[3]
Originally, one atomic mass unit was defined as one sixteenth of the mass of oxygen-16, but the atomic mass unit has since been redefined as one twelfth of the mass of carbon-12.