Gold Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! == Characteristics == [[File:Au atomic wire.jpg|thumb|left|Gold can be drawn into a monatomic wire, and then stretched more before it breaks.<ref name="Kizuka-2008" />]] [[File:Small gold nugget 5mm dia and corresponding foil surface of half sq meter.jpg|thumb|left|A gold nugget of {{convert|5|mm|abbr=on}} in size can be hammered into a [[gold foil]] of about {{convert|0.5|m2|abbr=on}} in area.]] Gold is the most [[malleable]] of all metals. It can be drawn into a wire of single-atom width, and then stretched considerably before it breaks.<ref name="Kizuka-2008">{{cite journal |last=Kizuka |first=Tokushi |title=Atomic configuration and mechanical and electrical properties of stable gold wires of single-atom width |url=https://tsukuba.repo.nii.ac.jp/record/16027/files/PRB-77_15.pdf |archive-url=https://web.archive.org/web/20210716175414/https://tsukuba.repo.nii.ac.jp/record/16027/files/PRB-77_15.pdf |archive-date=16 July 2021 |url-status=live |journal=Physical Review B |volume=77 |issue=15 |pages=155401 |date=1 April 2008 |bibcode=2008PhRvB..77o5401K|issn=1098-0121 |doi=10.1103/PhysRevB.77.155401 |hdl-access=free |hdl=2241/99261}}</ref> Such nanowires distort via the formation, reorientation, and migration of [[dislocation]]s and [[Crystal twinning|crystal twins]] without noticeable hardening.<ref>{{cite journal |last1=Che Lah |first1=Nurul Akmal |last2=Trigueros |first2=Sonia |title=Synthesis and modelling of the mechanical properties of Ag, Au and Cu nanowires |journal=[[Science and Technology of Advanced Materials]] |volume=20 |issue=1 |pages=225–261 |year=2019 |bibcode=2019STAdM..20..225L |pmid=30956731 |pmc=6442207 |doi=10.1080/14686996.2019.1585145}}</ref> A single gram of gold can be beaten into a sheet of {{convert|1|m2}}, and an [[avoirdupois ounce]] into {{convert|300|sqft|disp=flip}}. Gold leaf can be beaten thin enough to become semi-transparent. The transmitted light appears greenish-blue because gold strongly reflects yellow and red.<ref>{{cite web |url=http://www.webexhibits.org/causesofcolor/9.html |title=Gold: causes of color |access-date=6 June 2009}}</ref> Such semi-transparent sheets also strongly reflect [[infrared]] light, making them useful as infrared (radiant heat) shields in the visors of heat-resistant suits and in sun visors for [[spacesuit]]s.<ref>{{cite book |title=Suiting up for space: the evolution of the space suit |last=Mallan |first=Lloyd |date=1971 |publisher=John Day Co. |isbn=978-0-381-98150-1 |page=216}}</ref> Gold is a good [[Conduction (heat)|conductor of heat]] and [[Electrical conductor|electricity]]. Gold has a density of 19.3 g/cm<sup>3</sup>, almost identical to that of [[tungsten]] at 19.25 g/cm<sup>3</sup>; as such, tungsten has been used in the [[counterfeiting]] of [[gold bar]]s, such as by plating a tungsten bar with gold.<ref name="popsci">{{cite magazine |last=Gray |first=Theo |title=How to Make Convincing Fake-Gold Bars |url=http://www.popsci.com/diy/article/2008-03/how-make-convincing-fake-gold-bars |magazine=[[Popular Science]] |date=14 March 2008 |access-date=18 June 2008}}</ref><ref>Willie, Jim (18 November 2009) "[http://www.kitco.com/ind/willie/nov182009.html Zinc Dimes, Tungsten Gold & Lost Respect] {{webarchive |url=https://web.archive.org/web/20111008050729/http://www.kitco.com/ind/willie/nov182009.html |date=8 October 2011}}". Kitco</ref><ref>{{cite web |url=http://news.coinupdate.com/largest-private-refinery-discovers-gold-plated-tungsten-bar-0171/ |title=Largest Private Refinery Discovers Gold-Plated Tungsten Bar | Coin Update |website=news.coinupdate.com}}</ref><ref>{{cite news |title=Austrians Seize False Gold Tied to London Bullion Theft |work=[[The New York Times]] |access-date=25 March 2012 |date=22 December 1983 |url=https://www.nytimes.com/1983/12/22/world/austrians-seize-false-gold-tied-to-london-bullion-theft.html}}</ref> By comparison, the density of [[lead]] is 11.34 g/cm<sup>3</sup>, and that of the densest element, [[osmium]], is {{val|22.588|0.015|u=g/cm<sup>3</sup>}}.<ref name="Densest">{{cite journal |last=Arblaster |first=J. W. |title=Osmium, the Densest Metal Known |journal=Platinum Metals Review |volume=39 |issue=4 |date=1995 |page=164 |doi=10.1595/003214095X394164164 |s2cid=267393021 |url=http://www.technology.matthey.com/pdf/pmr-v39-i4-164-164.pdf |access-date=14 October 2016 |archive-date=18 October 2016 |archive-url=https://web.archive.org/web/20161018195547/http://www.technology.matthey.com/pdf/pmr-v39-i4-164-164.pdf |url-status=dead }}</ref><!-- 10.1038/nchem.1479 from 2012 gives same value--> === Color === {{Main|Colored gold}} [[File:Ag-Au-Cu-colours-english.svg|thumb|left|Different colors of [[Silver|Ag]]–Au–[[Copper|Cu]] alloys]] Whereas most metals are gray or silvery white, gold is slightly reddish-yellow.<ref name="chem">{{cite book |title=Encyclopædia of Chemistry, Theoretical, Practical, and Analytical, as Applied to the Arts and Manufacturers: Glass-zinc |url=https://books.google.com/books?id=o-FYAAAAYAAJ&pg=PA70 |year=1880 |publisher=J.B. Lippincott & Company |pages=70–}}</ref> This color is determined by the frequency of [[plasma oscillation]]s among the metal's valence electrons, in the ultraviolet range for most metals but in the visible range for gold due to [[relativistic quantum chemistry|relativistic effects]] affecting the [[atomic orbital|orbitals]] around gold atoms.<ref>{{cite web |url=http://math.ucr.edu/home/baez/physics/Relativity/SR/gold_color.html |title=Relativity in Chemistry |publisher=Math.ucr.edu |access-date=5 April 2009}}</ref><ref>{{Cite journal |first1=Hubert |last1=Schmidbaur |first2=Stephanie |last2=Cronje |first3=Bratislav |last3=Djordjevic |first4=Oliver |last4=Schuster |journal=Chemical Physics |volume=311 |pages=151–161 |title=Understanding gold chemistry through relativity |doi=10.1016/j.chemphys.2004.09.023 |date=2005 |issue=1–2 |bibcode=2005CP....311..151S}}</ref> Similar effects impart a golden hue to metallic [[caesium]]. Common colored gold alloys include the distinctive eighteen-karat [[rose gold]] created by the addition of copper. Alloys containing [[palladium]] or [[nickel]] are also important in commercial jewelry as these produce white gold alloys. Fourteen-karat gold-copper alloy is nearly identical in color to certain [[bronze]] alloys, and both may be used to produce police and other [[badge]]s. Fourteen- and eighteen-karat gold alloys with silver alone appear greenish-yellow and are referred to as [[green gold]]. Blue gold can be made by alloying with [[iron]], and purple gold can be made by alloying with [[aluminium]]. Less commonly, addition of [[manganese]], [[indium]], and other elements can produce more unusual colors of gold for various applications.<ref name="utilisegold" /> [[Colloidal gold]], used by electron-microscopists, is red if the particles are small; larger particles of colloidal gold are blue.<ref>{{Cite book |url=https://books.google.com/books?id=MzT9eWxtmRgC&pg=PA180 |title=Electron Microscopy in Microbiology |date=1988 |publisher=Academic Press |isbn=978-0-08-086049-7}}</ref> === 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="nubase">{{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 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="nubase" /> ==== 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=9781133709497 |page=273 |edition=13th}}</ref> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. 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