Editing Silver (section)

==Characteristics==
[[Image:1000oz.silver.bullion.bar.top.jpg|thumb|left|Silver bullion bar, 1000 ounces]]
[[File:Ag atomic wire.jpg|thumb|left|upright|Silver is extremely ductile, and can be drawn into a wire one atom wide.<ref>{{cite book |doi=10.5772/62288 |isbn=978-953-51-2252-4 |chapter=Combined Transmission Electron Microscopy – In situ Observation of the Formation Process and Measurement of Physical Properties for Single Atomic-Sized Metallic Wires |author=Masuda, Hideki |title=Modern Electron Microscopy in Physical and Life Sciences |editor=Janecek, Milos |editor2=Kral, Robert |publisher=InTech |year=2016|s2cid=58893669 }}</ref><!-- This is content from a predatory publisher (intechopen.com); recommend finding an alternative source for a comparable image, but I hesitate to remove the image at this time. -->]]
Silver is similar in its physical and chemical properties to its two vertical neighbours in [[group 11 element|group 11]] of the [[periodic table]]: [[copper]], and [[gold]]. Its 47 electrons are arranged in the [[electron configuration|configuration]] [Kr]4d<sup>10</sup>5s<sup>1</sup>, similarly to copper ([Ar]3d<sup>10</sup>4s<sup>1</sup>) and gold ([Xe]4f<sup>14</sup>5d<sup>10</sup>6s<sup>1</sup>); group 11 is one of the few groups in the [[d-block]] which has a completely consistent set of electron configurations.<ref name="Hammond-2004" /> This distinctive electron configuration, with a single electron in the highest occupied s [[Electron shell|subshell]] over a filled d subshell, accounts for many of the singular properties of metallic silver.<ref name="Greenwood and Earnshaw-5" />

Silver is a relatively soft and extremely [[Ductility|ductile]] and [[Malleability|malleable]] [[transition metal]], though it is slightly less malleable than gold. Silver crystallises in a [[face-centred cubic]] lattice with bulk coordination number 12, where only the single 5s electron is delocalised, similarly to copper and gold.<ref name="Greenwood and Earnshaw-6">Greenwood and Earnshaw, p. 1178</ref> Unlike metals with incomplete d-shells, metallic bonds in silver are lacking a [[covalent bond|covalent]] character and are relatively weak. This observation explains the low [[hardness]] and high ductility of [[monocrystalline|single crystals]] of silver.<ref name="Trigg-1992">{{cite book|author1=George L. Trigg|author2=Edmund H. Immergut|title=Encyclopedia of applied physics|url=https://books.google.com/books?id=sVQ5RAAACAAJ|access-date=2 May 2011|date=1992|publisher=VCH Publishers|isbn=978-3-527-28126-8|pages=267–72|volume=4: Combustion to Diamagnetism}}</ref>

Silver has a brilliant, white, metallic luster that can take a high [[polishing|polish]],<ref name="Austin, Alex-2007">{{cite book |title=The Craft of Silversmithing: Techniques, Projects, Inspiration |page=43 |author=Austin, Alex |isbn=978-1-60059-131-0 |date=2007 |publisher=Sterling Publishing Company, Inc.}}</ref> and which is so characteristic that the name of the metal itself has become a [[silver (color)|color name]].<ref name="Greenwood and Earnshaw-5">Greenwood and Earnshaw, p. 1177</ref> Protected silver has greater optical [[reflectivity]] than [[aluminium]] at all wavelengths longer than ~450&nbsp;nm.<ref name="Edwards-1936">{{cite journal|last1 = Edwards |first1=H.W. |last2 = Petersen |first2=R.P. |date = 1936|title = Reflectivity of evaporated silver films|journal = Physical Review |volume = 50|page=871|bibcode = 1936PhRv...50..871E|doi = 10.1103/PhysRev.50.871|issue = 9}}</ref> At wavelengths shorter than 450&nbsp;nm, silver's reflectivity is inferior to that of aluminium and drops to zero near 310&nbsp;nm.<ref name="Gemini Observatory">{{cite web |url=http://www.gemini.edu/sciops/telescopes-and-sites/optics/silver-vs-aluminum |title=Silver vs. Aluminum |access-date=1 August 2014 |publisher=Gemini Observatory}}</ref>

Very high electrical and thermal conductivity are common to the elements in group 11, because their single s electron is free and does not interact with the filled d subshell, as such interactions (which occur in the preceding transition metals) lower electron mobility.<ref>{{Cite book|title=Structure-Property Relations in Nonferrous Metals|first1=Alan M. |last1=Russell |first2=Kok Loong |last2= Lee |date=2005 |publisher=John Wiley & Sons |location=New York |isbn=9780471649526 |doi=10.1002/0471708542 |doi-access=free |page=302}}</ref> The [[thermal conductivity]] of silver is among the highest of all materials, although the thermal conductivity of [[carbon]] (in the [[diamond]] [[Allotropy|allotrope]]) and [[superfluid helium-4]] are higher.<ref name="Hammond-2004">{{cite book|last = Hammond|first = C. R.|title = The Elements, in Handbook of Chemistry and Physics|edition = 81st|publisher = CRC press|isbn = 978-0-8493-0485-9|year = 2004|url-access = registration|url = https://archive.org/details/crchandbookofche81lide}}</ref> The [[electrical conductivity]] of silver is the highest of all metals, greater even than copper. Silver also has the lowest [[contact resistance]] of any metal.<ref name="Hammond-2004" /> Silver is rarely used for its electrical conductivity, due to its high cost, although an exception is in [[radio-frequency engineering]], particularly at [[VHF]] and higher frequencies where silver plating improves electrical conductivity because those [[Skin effect|currents tend to flow on the surface of conductors]] rather than through the interior. During [[World War II]] in the US, {{gaps|13540}} tons of silver were used for the [[electromagnets]] in [[calutron]]s for enriching [[uranium]], mainly because of the wartime shortage of copper.<ref>{{cite book|last = Nichols |first=Kenneth D.|title = The Road to Trinity| page = 42|date =1987|location = Morrow, NY|isbn = 978-0-688-06910-0|publisher = Morrow}}</ref><ref>{{cite web|date = 11 September 2002 |url = http://www.tnengineering.net/AICHE/eastman-oakridge-young.htm |title = Eastman at Oak Ridge During World War II|last=Young |first=Howard |archive-url=https://web.archive.org/web/20120208054014/http://www.tnengineering.net/AICHE/eastman-oakridge-young.htm |archive-date=8 February 2012}}</ref><ref>{{cite journal|title = Not invented here? Check your history|last = Oman|first = H.|journal = IEEE Aerospace and Electronic Systems Magazine|date = 1992|volume = 7|issue = 1|pages = 51–53|doi = 10.1109/62.127132|s2cid = 22674885}}</ref>

Silver readily forms [[alloy]]s with copper, gold, and [[zinc]]. Zinc-silver alloys with low zinc concentration may be considered as face-centred cubic solid solutions of zinc in silver, as the structure of the silver is largely unchanged while the electron concentration rises as more zinc is added. Increasing the electron concentration further leads to [[body-centred cubic]] (electron concentration 1.5), [[cubic crystal system|complex cubic]] (1.615), and [[hexagonal close-packed]] phases (1.75).<ref name="Greenwood and Earnshaw-6" />

===Isotopes===
{{Main|Isotopes of silver}}

Naturally occurring silver is composed of two stable [[isotope]]s, <sup>107</sup>Ag and <sup>109</sup>Ag, with <sup>107</sup>Ag being slightly more abundant (51.839% [[natural abundance]]). This almost equal abundance is rare in the periodic table. The [[atomic weight]] is 107.8682(2) [[atomic mass unit|u]];<ref name="Atomic Weights of the Elements 2007">{{cite web|access-date = 11 November 2009|url = http://www.chem.qmul.ac.uk/iupac/AtWt/index.html|title = Atomic Weights of the Elements 2007 (IUPAC)|archive-url = https://web.archive.org/web/20170906114640/http://www.chem.qmul.ac.uk/iupac/AtWt/index.html|archive-date = 6 September 2017|url-status = dead}}</ref><ref>{{cite web|access-date = 11 November 2009|url = http://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=&ascii=html&isotype=some|title = Atomic Weights and Isotopic Compositions for All Elements (NIST)}}</ref> this value is very important because of the importance of silver compounds, particularly halides, in [[gravimetric analysis]].<ref name="Atomic Weights of the Elements 2007" /> Both isotopes of silver are produced in stars via the [[s-process]] (slow neutron capture), as well as in supernovas via the [[r-process]] (rapid neutron capture).<ref name="Cameron-1973">{{cite journal | last1 = Cameron |first1 = A.G.W. | year = 1973 | title = Abundance of the Elements in the Solar System | url = https://pubs.giss.nasa.gov/docs/1973/1973_Cameron_ca06310p.pdf | journal = Space Science Reviews | volume = 15 |issue = 1 | pages = 121–46 | doi = 10.1007/BF00172440 | bibcode = 1973SSRv...15..121C |s2cid = 120201972 }}</ref>

Twenty-eight [[radioisotope]]s have been characterised, the most stable being <sup>105</sup>Ag with a [[half-life]] of 41.29 days, <sup>111</sup>Ag with a half-life of 7.45 days, and <sup>112</sup>Ag with a half-life of 3.13 hours. Silver has numerous [[nuclear isomer]]s, the most stable being <sup>108m</sup>Ag (''t''<sub>1/2</sub> = 418 years), <sup>110m</sup>Ag (''t''<sub>1/2</sub> = 249.79 days) and <sup>106m</sup>Ag (''t''<sub>1/2</sub> = 8.28 days). All of the remaining [[radioactive]] isotopes have half-lives of less than an hour, and the majority of these have half-lives of less than three minutes.<ref name="Audi-2003">{{NUBASE 2003}}</ref>

Isotopes of silver range in [[Atomic weight|relative atomic mass]] from 92.950&nbsp;u (<sup>93</sup>Ag) to 129.950&nbsp;u (<sup>130</sup>Ag);<ref>{{cite web|access-date = 11 November 2009|url = http://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Ag&ascii=html&isotype=all|title = Atomic Weights and Isotopic Compositions for Silver (NIST)}}</ref> the primary [[decay mode]] before the most abundant stable isotope, <sup>107</sup>Ag, is [[electron capture]] and the primary mode after is [[beta decay]]. The primary [[decay product]]s before <sup>107</sup>Ag are [[palladium]] (element 46) isotopes, and the primary products after are [[cadmium]] (element 48) isotopes.<ref name="Audi-2003" />

The palladium [[isotope]] <sup>107</sup>Pd decays by beta emission to <sup>107</sup>Ag with a half-life of 6.5 million years. [[Iron meteorite]]s are the only objects with a high-enough palladium-to-silver ratio to yield measurable variations in <sup>107</sup>Ag abundance. [[Radiogenic]] <sup>107</sup>Ag was first discovered in the [[Santa Clara, Durango|Santa Clara]] meteorite in 1978.<ref>{{cite journal|doi = 10.1029/GL005i012p01079|title = Evidence for the existence of <sup>107</sup>Pd in the early solar system|date = 1978|last1 = Kelly |first1=William R. |journal = Geophysical Research Letters|volume = 5|pages = 1079–82|first2 = G. J.|last2 = Wasserburg|bibcode=1978GeoRL...5.1079K|issue = 12|url = http://authors.library.caltech.edu/43037/1/grl921.pdf}}</ref> <sup>107</sup>Pd–<sup>107</sup>Ag correlations observed in bodies that have clearly been melted since the [[accretion (astrophysics)|accretion]] of the [[Solar System]] must reflect the presence of unstable nuclides in the early Solar System.<ref>{{cite journal|title = Origin of Short-Lived Radionuclides|first1 = Sara S.|last1 = Russell|author1-link = Sara Russell|last2=Gounelle|first2=Matthieu|last3=Hutchison|first3=Robert|journal = [[Philosophical Transactions of the Royal Society A]]|volume = 359|issue = 1787|date = 2001 |pages = 1991–2004|doi = 10.1098/rsta.2001.0893|jstor=3066270|bibcode = 2001RSPTA.359.1991R |s2cid = 120355895}}</ref>