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! === 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> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Christianpedia:Copyrights for details). Do not submit copyrighted work without permission! Cancel Editing help (opens in new window) Discuss this page