Editing Metal (section)

===Formation===
{{See also|Nucleosynthesis}}
{{Periodic table (metal abundance in Earth crust)}}

Metallic elements up to the [[iron peak|vicinity of iron]] (in the periodic table) are largely made via [[stellar nucleosynthesis]]. In this process, lighter elements from hydrogen to [[silicon]] undergo successive [[nuclear fusion|fusion]] reactions inside stars, releasing light and heat and forming heavier elements with higher atomic numbers.<ref name="Cox">{{harvnb|Cox|1997|pp=73–89}}</ref>

Heavier elements are not usually formed this way since fusion reactions involving such nuclei would consume rather than release energy.<ref>{{harvnb|Cox|1997|pp=32, 63, 85}}</ref> Rather, they are largely synthesised (from elements with a lower atomic number) by [[neutron capture]], with the two main modes of this repetitive capture being the [[s-process]] and the [[r-process]]. In the s-process ("s" stands for "slow"), singular captures are separated by years or decades, allowing the less stable nuclei to [[beta decay]],<ref>{{harvnb|Podosek|2011|p=482}}</ref> while in the r-process ("rapid"), captures happen faster than nuclei can decay. Therefore the s-process takes a more-or-less clear path: for example, stable cadmium-110 nuclei are successively bombarded by free neutrons inside a star until they form cadmium-115 nuclei which are unstable and decay to form indium-115 (which is nearly stable, with a half-life {{val|30000}} times the age of the universe). These nuclei capture neutrons and form indium-116, which is unstable, and decays to form tin-116, and so on.<ref name="Cox" /><ref>{{harvnb|Padmanabhan|2001|p=234}}</ref>{{#tag:ref|In some cases, for example in the presence of [[photodisintegration|high energy gamma rays]] or in a [[rp-process|very high temperature hydrogen rich environment]], the subject nuclei may experience neutron loss or proton gain resulting in the production of (comparatively rare) [[p-nuclei|neutron deficient isotopes]].<ref>{{harvnb|Rehder|2010|pp=32, 33}}</ref>|group=n}} In contrast, there is no such path in the r-process. The s-process stops at bismuth due to the short half-lives of the next two elements, polonium and astatine, which decay to bismuth or lead. The r-process is so fast it can skip this zone of instability and go on to create heavier elements such as [[thorium]] and uranium.<ref>{{harvnb|Hofmann|2002|pp=23–24}}</ref>

Metals condense in planets as a result of stellar evolution and destruction processes. Stars lose much of their mass when it is [[stellar mass loss|ejected]] late in their lifetimes, and sometimes thereafter as a result of a [[neutron star]] merger,<ref>{{harvnb|Hadhazy|2016}}</ref>{{#tag:ref|The ejection of matter when two neutron stars collide is attributed to the interaction of their [[tidal force]]s, possible crustal disruption, and shock heating (which is what happens if you floor the accelerator in car when the engine is cold).<ref>{{harvnb|Choptuik|Lehner|Pretorias|2015|p=383}}</ref>|group=n}} thereby increasing the abundance of elements heavier than helium in the [[interstellar medium]]. When gravitational attraction causes this matter to coalesce and collapse [[nebular hypothesis|new stars and planets are formed]].<ref>{{harvnb|Cox|1997|pp=83, 91, 102–103}}</ref>