Editing Gold (section)

=== Isotopes ===
{{Main|Isotopes of gold}}
Gold has only one stable [[isotope]], {{chem|197|Au}}, which is also its only naturally occurring isotope, so gold is both a [[Mononuclidic element|mononuclidic]] and [[monoisotopic element]]. Thirty-six [[radioisotopes]] have been synthesized, ranging in [[atomic mass]] from 169 to 205. The most stable of these is {{chem|195|Au}} with a [[half-life]] of 186.1 days. The least stable is {{chem|171|Au}}, which decays by [[proton emission]] with a half-life of 30 μs. Most of gold's radioisotopes with atomic masses below 197 decay by some combination of [[proton emission]], [[alpha decay|α decay]], and [[β+ decay|β<sup>+</sup> decay]]. The exceptions are {{chem|195|Au}}, which decays by electron capture, and {{chem|196|Au}}, which decays most often by electron capture (93%) with a minor [[β− decay|β<sup>−</sup> decay]] path (7%).<ref>{{cite web |url=http://www.nndc.bnl.gov/nudat2/ |website=National Nuclear Data Center |title=Nudat 2 |access-date=12 April 2012}}</ref> All of gold's radioisotopes with atomic masses above 197 decay by β<sup>−</sup> decay.<ref name="Audi-2003">{{NUBASE 2003}}</ref>

At least 32 [[nuclear isomer]]s have also been characterized, ranging in atomic mass from 170 to 200. Within that range, only {{chem|178|Au}}, {{chem|180|Au}}, {{chem|181|Au}}, {{chem|182|Au}}, and {{chem|188|Au}} do not have isomers. Gold's most stable isomer is {{chem|198m2|Au}} with a half-life of 2.27 days. Gold's least stable isomer is {{chem|177m2|Au}} with a half-life of only 7&nbsp;ns. {{chem|184m1|Au}} has three decay paths: β<sup>+</sup> decay, [[isomeric transition]], and alpha decay. No other isomer or isotope of gold has three decay paths.<ref name="Audi-2003" />

==== Synthesis ====
{{See also|Synthesis of precious metals}}
The possible production of gold from a more common element, such as [[lead]], has long been a subject of human inquiry, and the ancient and medieval discipline of [[alchemy]] often focused on it; however, the transmutation of the chemical elements did not become possible until the understanding of [[nuclear physics]] in the 20th century. The first synthesis of gold was conducted by Japanese physicist [[Hantaro Nagaoka]], who synthesized gold from [[mercury (element)|mercury]] in 1924 by neutron bombardment.<ref>{{Cite journal |last1=Miethe |first1=A. |title=Der Zerfall des Quecksilberatoms |doi=10.1007/BF01505547 |journal=Die Naturwissenschaften |volume=12 |issue=29 |pages=597–598 |year=1924 |bibcode=1924NW.....12..597M|s2cid=35613814 }}</ref> An American team, working without knowledge of Nagaoka's prior study, conducted the same experiment in 1941, achieving the same result and showing that the [[isotopes of gold]] produced by it were all [[radioactive]].<ref>{{cite journal |last1=Sherr |first1=R. |first2=K. T. |last2=Bainbridge |first3=H. H. |last3=Anderson |name-list-style=amp |title=Transmutation of Mercury by Fast Neutrons |date=1941 |journal=[[Physical Review]] |volume=60 |issue=7 |pages=473–479 |doi=10.1103/PhysRev.60.473 |bibcode=1941PhRv...60..473S}}</ref> In 1980, [[Glenn T. Seaborg|Glenn Seaborg]] transmuted several thousand atoms of bismuth into gold at the Lawrence Berkeley Laboratory.<ref>{{Cite journal|last1=Aleklett |first1=K.|last2=Morrissey |first2=D.|last3=Loveland |first3=W.|last4=McGaughey |first4=P.|last5=Seaborg |first5=G.|year=1981|title=Energy dependence of <sup>209</sup>Bi fragmentation in relativistic nuclear collisions|journal=[[Physical Review C]]|volume=23 |issue=3 |page=1044|bibcode=1981PhRvC..23.1044A|doi=10.1103/PhysRevC.23.1044}}</ref><ref>{{cite news |url=https://www.telegraph.co.uk/education/4791069/The-Philosophers-Stone.html |newspaper=[[The Daily Telegraph]] |first=Robert |last=Matthews |title=The Philosopher's Stone |date=2 December 2001 |access-date=22 September 2020 }}</ref> Gold can be manufactured in a nuclear reactor, but doing so is highly impractical and would cost far more than the value of the gold that is produced.<ref>{{cite book |last1=Shipman |first1=James |last2=Wilson |first2=Jerry D. |last3=Higgins |first3=Charles A. |title=An Introduction to Physical Science |date=2012 |publisher=Cengage Learning |isbn=978-1-133-70949-7 |page=273 |edition=13th}}</ref>