Editing Aluminium (section)

=== Isotopes ===
{{Main|Isotopes of aluminium}}
Of aluminium isotopes, only {{SimpleNuclide|Aluminium}} is stable. This situation is common for elements with an odd atomic number.{{efn|No elements with odd atomic numbers have more than two stable isotopes; even-numbered elements have multiple stable isotopes, with tin (element 50) having the highest number of stable isotopes of all elements, ten. The single exception is [[beryllium]] which is even-numbered but has only one stable isotope.<ref name="IAEA" /> See [[Even and odd atomic nuclei]] for more details.}} It is the only [[primordial nuclide|primordial]] aluminium isotope, i.e. the only one that has existed on Earth in its current form since the formation of the planet. It is therefore a [[mononuclidic element]] and its [[standard atomic weight]] is virtually the same as that of the isotope. This makes aluminium very useful in [[nuclear magnetic resonance]] (NMR), as its single stable isotope has a high NMR sensitivity.{{sfn|Greenwood|Earnshaw|1997|pp=242–252}} The standard atomic weight of aluminium is low in comparison with many other metals.{{efn|Most other metals have greater standard atomic weights: for instance, that of iron is {{val|55.845}}; copper {{val|63.546}}; lead {{val|207.2}}.{{CIAAW2021}} which has consequences for the element's properties (see [[#Bulk|below]])}}

All other isotopes of aluminium are [[radioactive decay|radioactive]]. The most stable of these is [[Aluminium-26|<sup>26</sup>Al]]: while it was present along with stable <sup>27</sup>Al in the interstellar medium from which the Solar System formed, having been produced by [[stellar nucleosynthesis]] as well, its [[half-life]] is only 717,000&nbsp;years and therefore a detectable amount has not survived since the formation of the planet.<ref name="CIAAWaluminium"/> However, minute traces of <sup>26</sup>Al are produced from [[argon]] in the [[Earth's atmosphere|atmosphere]] by [[spallation]] caused by [[cosmic ray]] protons. The ratio of <sup>26</sup>Al to [[beryllium-10|<sup>10</sup>Be]] has been used for [[Radiometric dating|radiodating]] of geological processes over 10<sup>5</sup> to 10<sup>6</sup>&nbsp;year time scales, in particular transport, deposition, [[sediment]] storage, burial times, and erosion.<ref>{{cite book
|chapter-url=http://www.onafarawayday.com/Radiogenic/Ch14/Ch14-6.htm
|title=Radiogenic Isotope Geology
|last1=Dickin|first1=A.P.|date=2005
|publisher=Cambridge University Press|isbn=978-0-521-53017-0|chapter=''In situ'' Cosmogenic Isotopes
|archive-url=https://web.archive.org/web/20081206010805/http://www.onafarawayday.com/Radiogenic/Ch14/Ch14-6.htm|archive-date=6 December 2008|url-status=dead
|access-date=16 July 2008}}
</ref> Most meteorite scientists believe that the energy released by the decay of <sup>26</sup>Al was responsible for the melting and [[planetary differentiation|differentiation]] of some [[asteroids]] after their formation 4.55&nbsp;billion years ago.<ref>{{cite book
|title=Thunderstones and Shooting Stars
|url=https://archive.org/details/thunderstonessho00dodd_673|url-access=limited
|last1=Dodd|first1=R.T.|date=1986
|publisher=Harvard University Press|isbn=978-0-674-89137-1|pages=[https://archive.org/details/thunderstonessho00dodd_673/page/n99 89]–90}}</ref>

The remaining isotopes of aluminium, with [[mass number]]s ranging from 21 to 43, all have half-lives well under an hour. Three [[metastable]] states are known, all with half-lives under a minute.<ref name="IAEA">{{cite web
|url=https://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html
|title=Livechart – Table of Nuclides – Nuclear structure and decay data
|author=IAEA – Nuclear Data Section|year=2017|website=www-nds.iaea.org|publisher=[[International Atomic Energy Agency]]|access-date=31 March 2017
|archive-date=23 March 2019|archive-url=https://web.archive.org/web/20190323230752/https://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html|url-status=live}}</ref>