Editing Oxygen (section)

===Isotopes and stellar origin===
<!--COPYEDITS AND CORRECTIONS ONLY: DIRECT EXPANSION OF THIS SUBTOPIC TO [[Isotopes of oxygen]] -->
{{Main|Isotopes of oxygen}}
[[File:Evolved star fusion shells.svg|thumb|Late in a massive star's life, <sup>16</sup>O concentrates in the O-shell, <sup>17</sup>O in the H-shell and <sup>18</sup>O in the He-shell.|alt=A concentric-sphere diagram, showing, from the core to the outer shell, iron, silicon, oxygen, neon, carbon, helium and hydrogen layers.]]
Naturally occurring oxygen is composed of three stable [[isotope]]s, [[oxygen-16|<sup>16</sup>O]], [[oxygen-17|<sup>17</sup>O]], and [[oxygen-18|<sup>18</sup>O]], with <sup>16</sup>O being the most abundant (99.762% [[natural abundance]]).<ref name="EnvChem-Iso">{{cite web|url=http://environmentalchemistry.com/yogi/periodic/O-pg2.html|title=Oxygen Nuclides / Isotopes|publisher=EnvironmentalChemistry.com|access-date=December 17, 2007|archive-date=July 12, 2012|archive-url=https://archive.today/20120712195516/http://environmentalchemistry.com/yogi/periodic/O-pg2.html|url-status=live}}</ref>

Most <sup>16</sup>O is [[nucleosynthesis|synthesized]] at the end of the [[helium fusion]] process in massive [[star]]s but some is made in the [[neon burning process]].<ref name="Meyer2005">{{cite conference|first=B. S.|last=Meyer|title=Nucleosynthesis and Galactic Chemical Evolution of the Isotopes of Oxygen|conference=Workgroup on Oxygen in the Earliest Solar System|date=September 19–21, 2005|location=Gatlinburg, Tennessee|url=http://www.lpi.usra.edu/meetings/ess2005/pdf/9022.pdf|access-date=January 22, 2007|work=Proceedings of the NASA Cosmochemistry Program and the Lunar and Planetary Institute|conference-url=http://www.lpi.usra.edu/meetings/ess2005/|id=9022|archive-date=December 29, 2010|archive-url=https://web.archive.org/web/20101229194925/http://www.lpi.usra.edu/meetings/ess2005/pdf/9022.pdf|url-status=live}}</ref> <sup>17</sup>O is primarily made by the burning of hydrogen into [[helium]] during the [[CNO cycle]], making it a common isotope in the hydrogen burning zones of stars.<ref name="Meyer2005" /> Most <sup>18</sup>O is produced when [[Nitrogen-14|<sup>14</sup>N]] (made abundant from CNO burning) captures a [[Helium-4|<sup>4</sup>He]] nucleus, making <sup>18</sup>O common in the helium-rich zones of [[Stellar evolution#Massive stars|evolved, massive stars]].<ref name="Meyer2005" />

Fifteen [[radioisotope]]s have been characterized, ranging from <sup>11</sup>O to <sup>28</sup>O.{{NUBASE2020|ref}}<ref name=O-28-SA>{{cite news |url=https://www.sciencealert.com/scientists-have-observed-a-never-before-seen-form-of-oxygen |first=Michelle |last=Starr |date=30 August 2023 |title=Scientists Have Observed A Never-Before-Seen Form of Oxygen |work=ScienceAlert |access-date=30 August 2023}}</ref> The most stable are <sup>15</sup>O with a [[half-life]] of 122.24&nbsp;seconds and <sup>14</sup>O with a half-life of 70.606&nbsp;seconds.<ref name="EnvChem-Iso" /> All of the remaining [[Radioactive decay|radioactive]] isotopes have half-lives that are less than 27&nbsp;seconds and the majority of these have half-lives that are less than 83&nbsp;milliseconds.<ref name="EnvChem-Iso" /> The most common [[decay mode]] of the isotopes lighter than <sup>16</sup>O is [[positron emission|β<sup>+</sup> decay]]<ref name="NUDAT-13O">{{cite web|url=http://www.nndc.bnl.gov/nudat2/decaysearchdirect.jsp?nuc=13O&unc=nds|title=NUDAT 13O|access-date=July 6, 2009|archive-date=June 9, 2022|archive-url=https://web.archive.org/web/20220609000104/http://www.nndc.bnl.gov/nudat2/decaysearchdirect.jsp?nuc=13O|url-status=live}}</ref><ref name="NUDAT-14O">{{cite web|url=http://www.nndc.bnl.gov/nudat2/decaysearchdirect.jsp?nuc=14O&unc=nds|title=NUDAT 14O|access-date=July 6, 2009|archive-date=June 7, 2022|archive-url=https://web.archive.org/web/20220607045357/http://www.nndc.bnl.gov/nudat2/decaysearchdirect.jsp?nuc=14O|url-status=live}}</ref><ref name="NUDAT-15O">{{cite web|url=http://www.nndc.bnl.gov/nudat2/decaysearchdirect.jsp?nuc=15O&unc=nds|title=NUDAT 15O|access-date=July 6, 2009|archive-date=June 7, 2022|archive-url=https://web.archive.org/web/20220607045434/http://www.nndc.bnl.gov/nudat2/decaysearchdirect.jsp?nuc=15O|url-status=live}}</ref> to yield nitrogen, and the most common mode for the isotopes heavier than <sup>18</sup>O is [[beta decay]] to yield [[fluorine]].<ref name="EnvChem-Iso" />