Editing Group 12 element

{{short description|Group of chemical elements}}
{{Good article}}
{{Infobox periodic table group
| title       = Group&nbsp;12 {{nowrap|in the periodic table}}
| group number= 12
| trivial name=
| by element  = zinc group
| CAS         = IIB
| old IUPAC   = IIB
| mark        = Zn,Cd,Hg,Cn
| left        = [[Group 11 element|group 11]]
| right       = [[boron group]]}}
{| class="floatright"
! colspan=2 style="text-align:left;" | ↓&nbsp;<small>[[Period (periodic table)|Period]]</small>
|-
! [[Period 4 element|4]]
| {{element cell image|30|Zinc|Zn| |Solid|Transition metal|Primordial|image=Zinc fragment sublimed and 1cm3 cube.jpg|image caption=Zinc, fragment and sublimed 99.995%}}
|-
! [[Period 5 element|5]]
| {{element cell image|48|Cadmium|Cd| |Solid|Transition metal|Primordial|image=Cadmium-crystal bar.jpg|image caption=Cadmium, crystal bar 99.99%}}
|-
! [[Period 6 element|6]]
| {{element cell image|80|Mercury|Hg| |Liquid|Transition metal|link=Mercury (element)|Primordial|image=Pouring liquid mercury bionerd.jpg|image caption=Mercury, liquid}}
|-
! [[Period 7 element|7]]
| {{element cell image|112|Copernicium|Cn| |Unknown phase|Transition metal|Synthetic|legend=transition metal}}
|-
| colspan="2"|
----
''Legend''
{| style="text-align:center; border:0; margin:1em auto;"
|-
| style="border:{{element color|Primordial}}; background:{{Element color|table mark}}; padding:0 2px;" | [[primordial element]]
|-
| style="border:{{element color|Synthetic}}; background:{{Element color|table mark}}; padding:0 2px;" | [[synthetic element]]
|}
|}

'''Group 12''', by modern [[Group (periodic table)#CAS and old IUPAC numbering (A/B)|IUPAC]] numbering,<ref>{{cite journal |last1=Fluck |first1=E. |year=1988 |title=New Notations in the Periodic Table |journal=[[Pure and Applied Chemistry|Pure Appl. Chem.]] |volume=60 |pages=431–436 |doi=10.1351/pac198860030431 |url=http://www.iupac.org/publications/pac/1988/pdf/6003x0431.pdf |access-date=24 March 2012 |issue=3 |s2cid=96704008 }}</ref> is a [[Periodic table group|group]] of [[chemical element]]s in the [[periodic table group|periodic table]]. It includes [[zinc]] (Zn), [[cadmium]] (Cd), [[Mercury (element)|mercury]] (Hg),{{sfn|Greenwood|Earnshaw|1997|p=}}{{sfn|Cotton|Wilkinson|Murillo|Bochmann|1999|p=}}<ref>{{Housecroft3rd}}</ref> and [[copernicium]] (Cn).<ref name=07Ei01>{{cite journal |title=Chemical Characterization of Element 112 |journal=[[Nature (journal)|Nature]]|year=2007|volume=447|pages=72–75 |doi=10.1038/nature05761 |pmid=17476264 |last1=Eichler |first1=R. |last2=Aksenov |first2=N. V. |last3=Belozerov |first3=A. V. |last4=Bozhikov |first4=G. A. |last5=Chepigin |first5=V. I. |last6=Dmitriev |first6=S. N. |last7=Dressler |first7=R. |last8=Gäggeler |first8=H. W. |last9=Gorshkov |first9=V. A. |last10=Haenssler |first10=F. |last11=Itkis |first11=M. G. |last12=Laube |first12=A. |last13=Lebedev |first13=V. Ya. |last14=Malyshev |first14=O. N. |last15=Oganessian |first15=Yu. Ts. |last16=Petrushkin |first16=O. V. |last17=Piguet |first17=D. |last18=Rasmussen |first18=P. |last19=Shishkin |first19=S. V. |last20=Shutov |first20=A. V. |last21=Svirikhin |first21=A. I. |last22=Tereshatov |first22=E. E. |last23=Vostokin |first23=G. K. |last24=Wegrzecki |first24=M. |last25=Yeremin |first25=A. V. |display-authors=10 |issue=7140 |bibcode=2007Natur.447...72E|s2cid=4347419}}</ref> Formerly this group was named ''IIB'' (pronounced as "group two B", as the "II" is a [[Roman numeral]]) by [[Group (periodic table)#CAS and old IUPAC numbering (A/B)|CAS]] and old IUPAC system.{{refn|The name '''volatile metals''' for group 12 has occasionally been used,<ref>{{cite journal |last1=Simmons |first1=L. M. |date=December 1947 |title=A modification of the periodic table |journal=Journal of Chemical Education |volume=24 |issue=12 |pages=588 |doi=10.1021/ed024p588 |bibcode=1947JChEd..24..588S}}</ref> although this much more commonly refers to any metal having a high [[volatility (chemistry)|volatility]].|group=note}}

The three group 12 elements that occur naturally are zinc, cadmium and mercury. They are all widely used in electric and electronic applications, as well as in various alloys. The first two members of the group share similar properties as they are solid metals under standard conditions. Mercury is the only [[metal]] that is known to be a liquid at room temperature – as copernicium's boiling point has not yet been measured accurately enough,{{refn|group=note|refn={{val|340|10|u=K}} predicted, {{val|357|112|108|u=K}} experimentally<ref name=CRNL>{{cite journal |last1=Mewes |first1=J.-M. |last2=Smits |first2=O. R. |last3=Kresse |first3=G. |last4=Schwerdtfeger |first4=P. |title=Copernicium is a Relativistic Noble Liquid |journal=Angewandte Chemie International Edition  |date=2019 |volume=58 |issue=50 |pages=17964–17968 |doi=10.1002/anie.201906966 |pmid=31596013 |pmc=6916354 |url=https://www.researchgate.net/publication/336389017}}</ref>}} it is not yet known whether it is a liquid or a gas under standard conditions. While zinc is very important in the biochemistry of living organisms, cadmium and mercury are both highly toxic. As copernicium does not occur in nature, it has to be synthesized in the laboratory.

Due to their complete [[Electron shell|d-shell]] they are sometimes excluded from the [[transition metal]]s.

==Physical and atomic properties==
Like other [[group (periodic table)|groups]] of the [[periodic table]], the members of group 12 show patterns in its electron configuration, especially the outermost shells, which result in trends in their chemical behavior:
{| class="wikitable" style="white-space:nowrap;"
|-
!''[[Atomic number|Z]]'' !! [[Chemical element|Element]] !! Electrons per [[Electron shell|shell]]
|-
| 30 || zinc || 2, 8, 18, 2
|-
| 48 || cadmium || 2, 8, 18, 18, 2
|-
| 80 || mercury || 2, 8, 18, 32, 18, 2
|-
| 112 || copernicium || 2, 8, 18, 32, 32, 18, 2<br/>(predicted)
|}

The group 12 elements are all soft, [[diamagnetic]], [[divalent]] metals. They have the lowest melting points among all [[transition metals]].<ref name=ZincMetalProps/> Zinc is bluish-white and lustrous,<ref name="CRCp4-41">{{cite book |editor=David R. Lide |title=Handbook of Chemistry and Physics |edition=87th |year=2006 |publisher=CRC Press, Taylor & Francis Group |location=Boca Raton, Florida |isbn=978-0-8493-0487-3 |url=https://books.google.com/books?id=WDll8hA006AC |page=4{{hyphen}}41}}<!-- sic "-" not a range! --></ref> though most common commercial grades of the metal have a dull finish.<ref name="Heiserman1992p123">{{cite book |last=Heiserman |first=David L. |year=1992 |title=Exploring Chemical Elements and their Compounds |location=New York |publisher=TAB Books |isbn=978-0-8306-3018-9 |chapter=Element 30: Zinc |chapter-url=https://books.google.com/books?id=24l-Cpal9oIC |url=https://archive.org/details/exploringchemica01heis |page=123}}</ref> Zinc is also referred to in nonscientific contexts as ''[[spelter]]''.<ref name="Ingalls"/> Cadmium is soft, [[malleable]], [[ductile]], and with a bluish-white color. Mercury is a liquid, heavy, silvery-white metal. It is the only common liquid metal at ordinary temperatures, and as compared to other metals, it is a poor conductor of heat, but a fair conductor of electricity.<ref name=CRC>Hammond, C. R [http://www-d0.fnal.gov/hardware/cal/lvps_info/engineering/elements.pdf The Elements] in {{RubberBible86th}}</ref>

The table below is a summary of the key physical properties of the group 12 elements. The data for [[copernicium]] is based on relativistic density-functional theory simulations.<ref name=":0">{{Cite journal|last1=Mewes|first1=Jan-Michael|last2=Smits|first2=Odile R.|last3=Kresse|first3=Georg |last4=Schwerdtfeger|first4=Peter|date=2019|title=Copernicium: A Relativistic Noble Liquid |journal=Angewandte Chemie|volume=131|issue=50|pages=18132–18136 |doi=10.1002/ange.201906966|bibcode=2019AngCh.13118132M |issn=1521-3757 |doi-access=free}}</ref>

{| class="wikitable centered" style="text-align:center;"
|+Properties of the Group 12 elements| Properties of the group 12 elements
! Name
! Zinc
! Cadmium
! Mercury
! Copernicium
|-
| style="background:lightgrey; text-align:left;"|[[Melting point]]
| 693 [[Kelvin|K]] (420 [[Celsius|°C]]) || 594 K (321&nbsp;°C) || 234 K (−39&nbsp;°C) || 283±11 K<ref name=":0" /> (10&nbsp;°C)
|-
| style="background:lightgrey; text-align:left;"|[[Boiling point]]
| 1180 K (907&nbsp;°C) || 1040 K (767&nbsp;°C) || 630 K (357&nbsp;°C) || 340±10 K<ref name=":0" /> (60&nbsp;°C)
|-
| style="background:lightgrey; text-align:left;"|[[Density]]
| 7.14&nbsp;g·cm<sup>−3</sup> || 8.65&nbsp;g·cm<sup>−3</sup> || 13.534&nbsp;g·cm<sup>−3</sup> || 14.0&nbsp;g·cm<sup>−3</sup> <ref name=":0" />
|-
| style="background:lightgrey; text-align:left;"|Appearance
| silvery bluish-gray || silver-gray || silvery || ?
|-
| style="background:lightgrey; text-align:left;"|[[Atomic radius]]
| 135 pm || 155 pm || 150 pm || ? 147 pm
|}

Zinc is somewhat less dense than [[iron]] and has a hexagonal [[crystal structure]].{{sfn|Lehto|1968|p=826}} The metal is hard and brittle at most temperatures but becomes malleable between {{convert|100 and 150|C|F}}.<ref name="CRCp4-41"/><ref name="Heiserman1992p123"/> Above {{convert|210|C|F}}, the metal becomes brittle again and can be pulverized by beating.<ref>{{Cite book|title=The Useful Metals and Their Alloys |url=https://archive.org/details/usefulmetalsand00scofgoog|first=John|last=Scoffern|author-link=John Scoffern|pages=[https://archive.org/details/usefulmetalsand00scofgoog/page/n613 591]–603|publisher=Houlston and Wright|year=1861 |access-date=2009-04-06}}</ref> Zinc is a fair [[electrical conductivity|conductor of electricity]].<ref name="CRCp4-41"/> For a metal, zinc has relatively low melting ({{convert|419.5|C|F|disp=comma}}) and boiling points ({{convert|907|C|F|disp=comma}}).<ref name=ZincMetalProps>{{cite web |title=Zinc Metal Properties |url=http://www.galvanizeit.org/aga/designing-fabricating/design-considerations/zinc-metal-properties |publisher=American Galvanizers Association |year=2008 |access-date=2009-02-15 |url-status=dead |archive-url=https://web.archive.org/web/20090221111748/http://galvanizeit.org/aga/designing-fabricating/design-considerations/zinc-metal-properties |archive-date=February 21, 2009 }}</ref> Cadmium is similar in many respects to zinc but forms [[Complex (chemistry)|complex]] compounds.<ref>{{cite book |publisher=Walter de Gruyter|year=1985|edition=91–100|pages=1056–1057|isbn=978-3-11-007511-3 |title=Lehrbuch der Anorganischen Chemie|first1=Arnold F.|last1=Holleman|last2=Wiberg|first2=Egon |last3=Wiberg|first3=Nils|language=de|chapter=Cadmium}}</ref> Unlike other metals, cadmium is resistant to [[corrosion]] and as a result it is used as a protective layer when deposited on other metals. As a bulk metal, cadmium is insoluble in water and is not [[Flammability|flammable]]; however, in its powdered form it may burn and release toxic fumes.<ref name="ATSDR">{{cite web |title=Case Studies in Environmental Medicine (CSEM) Cadmium |url=http://www.atsdr.cdc.gov/csem/cadmium/cdcontents.html |publisher=Agency for Toxic Substances and Disease Registry |access-date=May 30, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110203222234/http://www.atsdr.cdc.gov/csem/cadmium/cdcontents.html |archive-date=February 3, 2011 }}</ref> Mercury has an exceptionally low melting temperature for a d-block metal. A complete explanation of this fact requires a deep excursion into [[quantum physics]], but it can be summarized as follows: mercury has a unique electronic configuration where electrons fill up all the available 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, 5s, 5p, 5d and 6s subshells. As such configuration strongly resists removal of an electron, mercury behaves similarly to [[noble gas]] elements, which form weak bonds and thus easily melting solids. The stability of the 6s shell is due to the presence of a filled 4f shell. An f shell poorly screens the nuclear charge that increases the attractive [[Coulomb's law|Coulomb interaction]] of the 6s shell and the nucleus (see [[lanthanide contraction]]). The absence of a filled inner f shell is the reason for the somewhat higher melting temperature of cadmium and zinc, although both these metals still melt easily and, in addition, have unusually low boiling points. [[Gold]] has atoms with one less 6s electron than mercury. Those electrons are more easily removed and are shared between the gold atoms forming relatively strong [[metallic bonds]].<ref name="Norrby">{{cite journal |author=Norrby, L.J.|title=Why is mercury liquid? Or, why do relativistic effects not get into chemistry textbooks?| journal= Journal of Chemical Education|volume=68|issue=2|page=110 |year=1991 |doi=10.1021/ed068p110 |bibcode=1991JChEd..68..110N}}</ref><ref>{{cite web|title=Why is mercury a liquid at STP? |url=http://antoine.frostburg.edu/chem/senese/101/periodic/faq/why-is-mercury-liquid.shtml|access-date=2009-07-07}}</ref>

Zinc, cadmium and mercury form a large range of [[alloy]]s. Among the zinc containing ones, [[brass]] is an alloy of zinc and [[copper]]. Other metals long known to form binary alloys with zinc are [[aluminium]], [[antimony]], [[bismuth]], [[gold]], iron, [[lead]], mercury, [[silver]], [[tin]], [[magnesium]], [[cobalt]], [[nickel]], [[tellurium]] and [[sodium]].<ref name="Ingalls">{{Cite book|title=Production and Properties of Zinc: A Treatise on the Occurrence and Distribution of Zinc Ore, the Commercial and Technical Conditions Affecting the Production of the Spelter, Its Chemical and Physical Properties and Uses in the Arts, Together with a Historical and Statistical Review of the Industry|last=Ingalls|first=Walter Renton |publisher=The Engineering and Mining Journal|year=1902|pages=[https://archive.org/details/productionandpr01ingagoog/page/n332 142]–6 |url=https://archive.org/details/productionandpr01ingagoog}}</ref> While neither zinc nor [[zirconium]] are [[Ferromagnetism|ferromagnetic]], their alloy {{chem|ZrZn|2}} exhibits ferromagnetism below 35&nbsp;[[Kelvin|K]].<ref name="CRCp4-41"/> Cadmium is used in many kinds of [[solder]] and bearing alloys, due to a low [[coefficient of friction]] and fatigue resistance.<ref name="HgCdPb"/> It is also found in some of the lowest-melting alloys, such as [[Wood's metal]].<ref>{{cite book|first1= George Stuart|last1= Brady|first2= George S.|last2= Brady|first3= Henry R.|last3= Clauser|first4 = John A.|last4 = Vaccari|isbn = 978-0-07-136076-0|url = https://books.google.com/books?id=vIhvSQLhhMEC&pg=PA425|title = Materials handbook: an encyclopedia for managers, technical professionals, purchasing and production managers, technicians, and supervisors|publisher = McGraw-Hill Professional|year = 2002| page = 425}}</ref> Because it is a liquid, mercury dissolves other metals and the alloys that are formed are called [[amalgam (chemistry)|amalgams]]. For example, such amalgams are known with gold, zinc, sodium, and many other metals. Because iron is an exception, iron flasks have been traditionally used to trade mercury. Other metals that do not form amalgams with mercury include [[tantalum]], [[tungsten]] and [[platinum]]. [[Sodium amalgam]] is a common reducing agent in [[organic synthesis]], and is also used in [[high-pressure sodium]] lamps. Mercury readily combines with [[aluminium]] to form a [[aluminium amalgam|mercury-aluminium amalgam]] when the two pure metals come into contact. Since the amalgam reacts with air to give aluminium oxide, small amounts of mercury corrode aluminium. For this reason, mercury is not allowed aboard an aircraft under most circumstances because of the risk of it forming an amalgam with exposed aluminium parts in the aircraft.<ref name="CorrAl">{{cite book |author1=Vargel, C. |author2=Jacques, M. |author3=Schmidt, M. P. | title = Corrosion of Aluminium|year =2004| isbn = 978-0-08-044495-6|publisher = Elsevier |url=https://books.google.com/books?id=NAABS5KrVDYC&pg=PA158|page=158}}</ref>

==Chemistry==
Most of the chemistry has been observed only for the first three members of the group 12. The chemistry of copernicium is not well established and therefore the rest of the section deals only with zinc, cadmium and mercury.

===Periodic trends===
All elements in this group are [[metal]]s. The similarity of the metallic radii of cadmium and mercury is an effect of the [[lanthanide contraction]]. So, the trend in this group is unlike the trend in group 2, the [[alkaline earth]]s, where metallic radius increases smoothly from top to bottom of the group. All three metals have relatively low melting and boiling points, indicating that the [[metallic bond]] is relatively weak, with relatively little overlap between the [[valence band]] and the [[conduction band]].<ref name = "chemyst">{{cite web |url=http://www.alchemyst.co.uk/alchemystry/pdf/Inorganic/descriptive_pblock.pdf |title= Descriptive P-block Notes|author=Moss, Alex |year=2003 |publisher=Alchemyst Online|access-date=June 2, 2011}}</ref> Thus, zinc is close to the boundary between metallic and [[metalloid]] elements, which is usually placed between [[gallium]] and [[germanium]], though gallium participates in [[semi-conductor]]s such as [[gallium arsenide]].

Zinc and cadmium are [[Electropositivity|electropositive]] while mercury is not.<ref name = "chemyst"/> As a result, zinc and cadmium metal are good reducing agents. The elements of group 12 have an oxidation state of +2 in which the ions have the rather stable d<sup>10</sup> electronic configuration, with a full [[electron shell|sub-shell]]. However, mercury can easily be reduced to the +1 oxidation state; usually, as in the ion {{chem|Hg|2|2+}}, two mercury(I) ions come together to form a metal-metal bond and a [[diamagnetic]] species.<ref>{{cite journal |last1=Lindberg |first1=S. E. |last2=Stratton |first2=W. J. |year=1998 |title=Atmospheric Mercury Speciation: Concentrations and Behavior of Reactive Gaseous Mercury in Ambient Air|journal=Environmental Science and Technology |volume=32 |issue=1 |doi=10.1021/es970546u |pages=49–57 |bibcode = 1998EnST...32...49L }}</ref> Cadmium can also form species such as [Cd<sub>2</sub>Cl<sub>6</sub>]<sup>4−</sup> in which the metal's oxidation state is +1. Just as with mercury, the formation of a metal-metal bond results in a diamagnetic compound in which there are no unpaired electrons; thus, making the species very reactive. Zinc(I) is known mostly in the gas phase, in such compounds as linear Zn<sub>2</sub>Cl<sub>2</sub>, analogous to [[calomel]].  In the solid phase, the rather exotic compound [[decamethyldizincocene]] (Cp*Zn–ZnCp*) is known.

===Classification===
The elements in group 12 are usually considered to be [[d-block]] elements, but not [[transition element]]s as the d-shell is full. Some authors classify these elements as [[main-group element]]s because the [[valence electron]]s are in ns<sup>2</sup> orbitals. Nevertheless, they share many characteristics with the neighboring [[group 11 element]]s on the periodic table, which are almost universally considered to be transition elements. For example, zinc shares many characteristics with the neighboring transition metal, copper. Zinc complexes merit inclusion in the [[Irving-Williams series]] as zinc forms many complexes with the same [[stoichiometry]] as complexes of copper(II), albeit with smaller [[stability constants of complexes|stability constants]].<ref>{{cite journal |last1=Al-Niaimi |first1=N. S. |last2=Hamid|first2=H. A. |year=1976 |title=Stabilities of nickel(II), copper(II), zinc(II) and dioxouranium(II) complexes of some β-diketones  |journal= Journal of Inorganic and Nuclear Chemistry |volume=3 |issue=5|doi=10.1016/0022-1902(77)80167-X |pages=849–852 }}</ref> There is little similarity between cadmium and silver as compounds of silver(II) are rare and those that do exist are very strong oxidizing agents. Likewise the common oxidation state for gold is +3, which precludes there being much common chemistry between mercury and gold, though there are similarities between mercury(I) and gold(I) such as the formation of linear dicyano complexes, [M(CN)<sub>2</sub>]<sup>−</sup>. According to [[IUPAC]]'s definition of transition metal as ''an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell'',<ref>{{GoldBookRef |title=transition element |file=T06456 }}</ref> zinc and cadmium are not transition metals, while mercury is. This is because only mercury is known to have a compound where its oxidation state is higher than +2, in [[mercury(IV) fluoride]] (though its existence is disputed, as later experiments trying to confirm its synthesis could not find evidence of HgF<sub>4</sub>).<ref>[http://www.speciation.net/News/Elusive-HgIV-species-has-been-synthesized-under-cryogenic-conditions-;~/2007/10/12/3303.html Elusive Hg(IV) species has been synthesized under cryogenic conditions]</ref><ref>{{cite journal|doi=10.1002/ange.200703710|title=Mercury is a Transition Metal: The First Experimental Evidence for HgF4|year=2007|last1=Wang|first1=Xuefang|last2=Andrews|first2=Lester|last3=Riedel|first3=Sebastian|last4=Kaupp|first4=Martin|journal=Angewandte Chemie|volume=119|issue=44|pages=8523–8527|bibcode=2007AngCh.119.8523W }}</ref> However, this classification is based on one highly atypical compound seen at non-equilibrium conditions and is at odds to mercury's more typical chemistry, and Jensen has suggested that it would be better to regard mercury as not being a transition metal.<ref name=Jensen/>

===Relationship with the alkaline earth metals===
Although group 12 lies in the [[d-block]] of the modern 18-column periodic table, the d electrons of zinc, cadmium, and (almost always) mercury behave as core electrons and do not take part in bonding. This behavior is similar to that of the [[main-group element]]s, but is in stark contrast to that of the neighboring [[group 11 element]]s ([[copper]], [[silver]], and [[gold]]), which also have filled d-subshells in their ground-state [[electron configuration]] but behave chemically as transition metals. For example, the bonding in [[chromium(II) sulfide]] (CrS) involves mainly the 3d electrons; that in [[iron(II) sulfide]] (FeS) involves both the 3d and 4s electrons; but that of [[zinc sulfide]] (ZnS) involves only the 4s electrons and the 3d electrons behave as core electrons. Indeed, useful comparison can be made between their properties and the first two members of [[alkaline earth metal|group 2]], [[beryllium]] and [[magnesium]], and in earlier short-form periodic table layouts, this relationship is illustrated more clearly. For instance, zinc and cadmium are similar to beryllium and magnesium in their [[atomic radius|atomic radii]], [[ionic radius|ionic radii]], [[electronegativity|electronegativities]], and also in the structure of their [[binary compound]]s and their ability to form complex ions with many [[nitrogen]] and [[oxygen]] [[ligand]]s, such as complex [[hydride]]s and [[amine]]s. However, beryllium and magnesium are small atoms, unlike the heavier [[alkaline earth metal]]s and like the group 12 elements (which have a greater nuclear charge but the same number of [[valence electron]]s), and the [[periodic trend]]s down group 2 from beryllium to [[radium]] (similar to that of the [[alkali metal]]s) are not as smooth when going down from beryllium to mercury (which is more similar to that of the p-block main groups) due to the [[d-block contraction|d-block]] and [[lanthanide contraction]]s. It is also the d-block and lanthanide contractions that give mercury many of its distinctive properties.<ref name="Jensen">{{cite journal|author1-link=William B. Jensen|last1=Jensen |first1=William B. |year=2003 |title=The Place of Zinc, Cadmium, and Mercury in the Periodic Table |journal=Journal of Chemical Education |volume=80 |issue=8 |pages=952–961 |doi=10.1021/ed080p952 |bibcode=2003JChEd..80..952J |url=http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/091.%20Zn-Cd-Hg.pdf |access-date=2012-05-06 |url-status=dead |archive-url=https://web.archive.org/web/20100611152417/http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/091.%20Zn-Cd-Hg.pdf |archive-date=2010-06-11 }}</ref>
{| class="wikitable centered" style="text-align:center;"
|+Comparison of the properties of the alkaline earth metals and the group 12 elements (predictions for copernicium)<ref name="Jensen"/>
! Name
! Beryllium
! Magnesium
! Calcium
! Strontium
! Barium
! Radium
|-
| style="background:lightgrey; text-align:left;"|[[Valence electron]] configuration
| 2s<sup>2</sup> || 3s<sup>2</sup> || 4s<sup>2</sup> || 5s<sup>2</sup> || 6s<sup>2</sup> || 7s<sup>2</sup>
|-
| style="background:lightgrey; text-align:left;"|Core electron configuration
| &#91;[[Helium|He]]&#93; || &#91;[[Neon|Ne]]&#93; || &#91;[[Argon|Ar]]&#93; || &#91;[[Krypton|Kr]]&#93; || &#91;[[Xenon|Xe]]&#93; || &#91;[[Radon|Rn]]&#93;
|-
| style="background:lightgrey; text-align:left;"|[[Oxidation state]]s<ref group="note" name="oxidation-states">See [[list of oxidation states of the elements]]. Oxidation states in '''bold''' are common.</ref>
| '''+2''', +1 || '''+2''', +1 || '''+2''', +1 || '''+2''', +1 || '''+2''' || '''+2'''
|-
| style="background:lightgrey; text-align:left;"|[[Melting point]]
| 1560 [[Kelvin|K]] (1287 [[Celsius|°C]]) || 923 K (650&nbsp;°C) || 1115 K (842&nbsp;°C) || 1050 K (777&nbsp;°C) || 1000 K (727&nbsp;°C) || 973 K (700&nbsp;°C)
|-
| style="background:lightgrey; text-align:left;"|[[Boiling point]]
| 2742 K (2469&nbsp;°C) || 1363 K (1090&nbsp;°C) || 1757 K (1484&nbsp;°C) || 1655 K (1382&nbsp;°C) || 2170 K (1897&nbsp;°C) || 2010 K (1737&nbsp;°C)
|-
| style="background:lightgrey; text-align:left;"|Appearance
| white-gray metallic || shiny gray metallic || dull silver-gray || silvery white metallic || silvery gray || silvery white metallic
|-
| style="background:lightgrey; text-align:left;"|[[Density]]
| 1.85&nbsp;g·cm<sup>−3</sup> || 1.738&nbsp;g·cm<sup>−3</sup> || 1.55&nbsp;g·cm<sup>−3</sup> || 2.64&nbsp;g·cm<sup>−3</sup> || 3.51&nbsp;g·cm<sup>−3</sup> || 5.5&nbsp;g·cm<sup>−3</sup>
|-
| style="background:lightgrey; text-align:left;"|Pauling [[electronegativity]]
| 1.57 || 1.31 || 1.00 || 0.95 || 0.89 || 0.9
|-
| style="background:lightgrey; text-align:left;"|[[Atomic radius]]
| 105 pm || 150 pm || 180 pm || 200 pm || 215 pm || 215 pm
|-
| style="background:lightgrey; text-align:left;"|Crystal [[ionic radius]]
| 59 pm || 86 pm || 114 pm || 132 pm || 149 pm || 162 pm
|-
| style="background:lightgrey; text-align:left;"|[[Flame test]] color
| white<ref name="Jensen"/> || brilliant white<ref name="rsc">{{cite web|url=http://www.rsc.org/chemsoc/visualelements/PAGES/data/intro_groupii_data.html |title=Visual Elements: Group 2–The Alkaline Earth Metals |author=Royal Society of Chemistry |work=Visual Elements |publisher=Royal Society of Chemistry|access-date=13 January 2012|author-link=Royal Society of Chemistry }}</ref> || brick-red<ref name="rsc"/> || crimson<ref name="rsc"/> || apple green<ref name="rsc"/> || crimson red{{refn|The color of the flame test of pure radium has never been observed; the crimson red color is an extrapolation from the flame test color of its compounds.<ref name="RaFlameTest">{{cite book | url = https://books.google.com/books?id=3cgQLgEACAAJ | title = The Radiochemistry of Radium | last1 = Kirby | first1 = H. W. | last2 = Salutsky | first2 = Murrell L. | year = 1964 | publisher = National Academies Press }}{{Dead link|date=May 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>|group=note}}
|-
| style="background:lightgrey; text-align:left;"|[[Organometallic chemistry]]
| good || good || poor || very poor || very poor || extremely poor
|-
| style="background:lightgrey; text-align:left;"|[[Hydroxide]]
| [[amphoteric]] || [[base (chemistry)|basic]] || basic || strongly basic || strongly basic || strongly basic
|-
| style="background:lightgrey; text-align:left;"|[[Oxide]]
| amphoteric || strongly basic || strongly basic || strongly basic || strongly basic || strongly basic
|-
! Name
! Beryllium
! Magnesium
! Zinc
! Cadmium
! Mercury
! Copernicium
|-
| style="background:lightgrey; text-align:left;"|Valence electron configuration
| 2s<sup>2</sup> || 3s<sup>2</sup> || 4s<sup>2</sup> || 5s<sup>2</sup> || 6s<sup>2</sup> || ? 7s<sup>2</sup>
|-
| style="background:lightgrey; text-align:left;"|Core electron configuration
| [He] || [Ne] || [Ar]3d<sup>10</sup> || [Kr]4d<sup>10</sup> || [Xe]4f<sup>14</sup>5d<sup>10</sup> || ? [Rn]5f<sup>14</sup>6d<sup>10</sup>
|-
| style="background:lightgrey; text-align:left;"|Oxidation states<ref group="note" name="oxidation-states"/>
| '''+2''', +1 || '''+2''', +1 || '''+2''', +1 || '''+2''', +1 || '''+2''', '''+1''' || ? '''+4''', '''+2''', '''+1''', '''0'''<ref name="superheavy chemistry">{{Cite web|author=H. W. Gäggeler |title=Gas Phase Chemistry of Superheavy Elements |year=2007 |pages=26–28 |publisher=[[Paul Scherrer Institute]] |url=http://lch.web.psi.ch/files/lectures/TexasA&M/TexasA&M.pdf |url-status=dead |archive-url=https://web.archive.org/web/20120220090755/http://lch.web.psi.ch/files/lectures/TexasA%26M/TexasA%26M.pdf |archive-date=2012-02-20 }}</ref><ref name="Haire">{{cite book| title = The Chemistry of the Actinide and Transactinide Elements| editor1-last = Morss|editor2-first = Norman M.| editor2-last = Edelstein| editor3-last = Fuger|editor3-first = Jean| last = Haire|first = Richard G.| chapter = Transactinides and the future elements| publisher = [[Springer Science+Business Media]]| year = 2006| page = 1675| isbn = 978-1-4020-3555-5| location = Dordrecht, The Netherlands| edition = 3rd}}</ref><ref name=BFricke>{{cite book |last1=Fricke |first1=Burkhard |year=1975 |title=Superheavy elements: a prediction of their chemical and physical properties |journal=Recent Impact of Physics on Inorganic Chemistry |volume=21 |pages=[https://archive.org/details/recentimpactofph0000unse/page/89 89–144] |doi=10.1007/BFb0116498 |url=https://archive.org/details/recentimpactofph0000unse/page/89 |access-date=4 October 2013 |series=Structure and Bonding |isbn=978-3-540-07109-9 }}</ref>
|-
| style="background:lightgrey; text-align:left;"|Melting point
| 1560 K (1287&nbsp;°C) || 923 K (650&nbsp;°C) || 693 K (420&nbsp;°C) || 594 K (321&nbsp;°C) || 234 K (−39&nbsp;°C) || 283±11 K (10&nbsp;°C)
|-
| style="background:lightgrey; text-align:left;"|Boiling point
| 2742 K (2469&nbsp;°C) || 1363 K (1090&nbsp;°C) || 1180 K (907&nbsp;°C) || 1040 K (767&nbsp;°C) || 630 K (357&nbsp;°C) || 340±10 K (60&nbsp;°C)
|-
| style="background:lightgrey; text-align:left;"|Appearance
| white-gray metallic || shiny gray metallic || silvery bluish-gray metallic || silver-gray || silvery || ?
|-
| style="background:lightgrey; text-align:left;"|Density
| 1.85&nbsp;g·cm<sup>−3</sup> || 1.738&nbsp;g·cm<sup>−3</sup> || 7.14&nbsp;g·cm<sup>−3</sup> || 8.65&nbsp;g·cm<sup>−3</sup> || 13.534&nbsp;g·cm<sup>−3</sup> || 14.0&nbsp;g·cm<sup>−3</sup>
|-
| style="background:lightgrey; text-align:left;"|Pauling electronegativity
| 1.57 || 1.31 || 1.65 || 1.69 || 2.00 || ?
|-
| style="background:lightgrey; text-align:left;"|Atomic radius
| 105 pm || 150 pm || 135 pm || 155 pm || 150 pm || ? 147 pm<ref name="Haire"/>
|-
| style="background:lightgrey; text-align:left;"|Crystal ionic radius
| 59 pm || 86 pm || 88 pm || 109 pm || 116 pm || ? 75 pm<ref name="Haire"/>
|-
| style="background:lightgrey; text-align:left;"|Flame test color
| white || brilliant white || bluish-green{{refn|Sometimes reported as white.<ref name="Jensen"/>|group="note"}} || ? || ? || ?
|-
| style="background:lightgrey; text-align:left;"|Organometallic chemistry
| good || good || good || good || good || ?
|-
| style="background:lightgrey; text-align:left;"|Hydroxide
| amphoteric || basic || amphoteric || weakly basic || ? || ?
|-
| style="background:lightgrey; text-align:left;"|Oxide
| amphoteric || strongly basic || amphoteric || mildly basic || mildly basic || ?
|}

===Compounds===
{{see also|Compounds of zinc|Organozinc compounds|Organocadmium compound|Organomercury}}
All three metal ions form many [[Tetrahedral molecular geometry|tetrahedral]] species, such as {{chem|MCl|4|2-}}. Both zinc and cadmium can also form octahedral complexes such as the [[Metal ions in aqueous solution|aqua ions]] [M(H<sub>2</sub>O)<sub>6</sub>]<sup>2+</sup> which are present in aqueous solutions of salts of these metals.<ref>{{cite book |last= Richens |first= David T. |title=The Chemistry of Aqua Ions |publisher=J. Wiley  |date=September 1997 |isbn= 978-0-471-97058-3}}</ref> Covalent character is achieved by using the s and p orbitals. Mercury, however, rarely exceeds a [[coordination number]] of four. Coordination numbers of 2, 3, 5, 7 and 8 are also known.

==History==
The elements of group 12 have been found throughout history, being used since ancient times to being discovered in laboratories.  The group itself has not acquired a [[trivial name]], but it has been called ''group IIB'' in the past.

===Zinc===
Zinc has been found being used in impure forms in ancient times as well as in alloys such as brass that have been found to be over 2000 years old.{{sfn|Weeks|1933|p=20}}{{sfn|Greenwood|Earnshaw|1997|p=1201}} Zinc was distinctly recognized as a metal under the designation of ''Fasada'' in the medical Lexicon ascribed to the Hindu king Madanapala (of Taka dynasty) and written about the year 1374.<ref name="Ray1903">{{cite book |last=Ray|first=Prafulla Chandra|title=A History of Hindu Chemistry from the Earliest Times to the Middle of the Sixteenth Century, A.D.: With Sanskrit Texts, Variants, Translation and Illustrations |publisher=The Bengal Chemical & Pharmaceutical Works |year=1903|edition=2nd|volume=1|pages=157–158 |url=https://books.google.com/books?id=DL1HAAAAIAAJ}} (public domain text)</ref> The metal was also of use to [[Alchemy|alchemists]].<ref>{{Cite book|last=Arny|first=Henry Vinecome|title=Principles of Pharmacy|url=https://archive.org/details/principlespharm01arnygoog|publisher=W. B. Saunders company |year=1917|edition=2nd|page=[https://archive.org/details/principlespharm01arnygoog/page/n487 483]}}</ref> The name of the metal was first documented in the 16th century,<ref name="iza">{{cite web |last=Habashi|first=Fathi|title=Discovering the 8th Metal |publisher=International Zinc Association (IZA) |url=http://www.iza.com/Documents/Communications/Publications/History.pdf|access-date=2008-12-13|archive-url=https://web.archive.org/web/20090304154217/http://www.iza.com/Documents/Communications/Publications/History.pdf|archive-date=2009-03-04|url-status=dead}}</ref><ref>{{Cite book|title=Georgius Agricola de Re Metallica |first=Herbert Clark|last=Hoover|publisher=Kessinger Publishing|year=2003|page=409|isbn=978-0-7661-3197-2}}</ref> and is probably derived from the German {{lang|de|zinke}} for the needle-like appearance of metallic crystals.<ref>{{Cite book|title=Ullmann's Encyclopedia of Industrial Chemistry |last=Gerhartz|edition=5th|year=1996|isbn=978-3-527-20100-6 |publisher=VHC|page=509|first=Wolfgang}}</ref>

[[File:Zinc symbol (fixed width).svg|thumb|right|Alchemical symbol for the element zinc]]

The isolation of metallic zinc in the West may have been achieved independently by several people in the 17th century.{{sfn|Emsley|2001|p=502}} German chemist [[Andreas Sigismund Marggraf|Andreas Marggraf]] is usually given credit for discovering pure metallic zinc in a 1746 experiment by heating a mixture of [[calamine]] and charcoal in a closed vessel without copper to obtain a metal.{{sfn|Weeks|1933|p=21}} Experiments on frogs by the Italian doctor [[Luigi Galvani]] in 1780 with brass paved the way for the discovery of [[Battery (electricity)|electrical batteries]], galvanization and [[cathodic protection]].<ref name="ExcelPhysics">{{Cite book |title=Excel Preliminary Physics|last=Warren|first=Neville G.|publisher=Pascal Press|year=2000|page=47|isbn=978-1-74020-085-1|url=https://books.google.com/books?id=eL9Xn6nQ6XQC}}</ref><ref name=IntEncyl>{{Cite book |title=The New International Encyclopaedia|chapter=Galvanic Cell|page=80|year=1903|publisher=Dodd, Mead and Company|chapter-url=https://books.google.com/books?id=gV1MAAAAMAAJ&pg=PA80}}</ref> In 1799, Galvani's friend, [[Alessandro Volta]], invented the [[Voltaic pile]].<ref name="ExcelPhysics"/> The biological importance of zinc was not discovered until 1940 when [[carbonic anhydrase]], an enzyme that scrubs carbon dioxide from blood, was shown to have zinc in its [[active site]].{{sfn|Cotton|Wilkinson|Murillo|Bochmann|1999|p=626}}

===Cadmium===
In 1817, cadmium was discovered in Germany as an impurity in [[zinc carbonate]] minerals (calamine) by [[Friedrich Stromeyer]] and [[Karl Samuel Leberecht Hermann]].<ref>{{cite book|chapter = Cadmium |title = Kirk-Othmer Encyclopedia of Chemical Technology |edition = 4th |place=New York |publisher = John Wiley & Sons |year=1994 |volume= 5}}</ref> It was named after the Latin ''cadmia'' for "[[calamine]]", a cadmium-bearing mixture of minerals, which was in turn named after the Greek mythological character, Κάδμος [[Cadmus]], the founder of [[Ancient Thebes (Boeotia)|Thebes]].<ref>{{cite journal|journal = Annalen der Physik|year = 1818|pages = 113–116|volume = 59|title = Noch ein schreiben über das neue Metall (Another letter about the new metal)|author = Hermann|url = http://gallica.bnf.fr/ark:/12148/bpt6k150680/f125.chemindefer|bibcode = 1818AnP....59..113H |doi = 10.1002/andp.18180590511|issue = 5 }}</ref> Stromeyer eventually isolated cadmium metal by [[Roasting (metallurgy)|roasting]] and reduction of the [[cadmium sulfide|sulfide]].<ref>{{cite book|url = https://books.google.com/books?id=84VAAAAAYAAJ&pg=PA122|page = 122|title = Cyclopædia of commerce, mercantile law, finance, commercial geography and navigation|author1 = Waterston, William|author2 = Burton, J. H|year = 1844}}</ref><ref>{{cite book|url = https://books.google.com/books?id=Q-cHAAAAQAAJ&pg=PA10|page = 10|title = The art of landscape painting in water colours, by T. and T. L. Rowbotham|author1 = Rowbotham, Thomas Leeson|year = 1850}}</ref><ref name="Cadold">{{cite book|pages = 135–141|url = https://books.google.com/books?id=gGHOz1G3AqwC&pg=PA135|title = The life cycle of copper, its co-products and byproducts|isbn = 978-1-4020-1552-6|author1 = Ayres, Robert U.|author2 = Ayres, Leslie|author3 = Råde, Ingrid|year = 2003| publisher=Springer }}</ref>

In 1927, the [[Bureau International des Poids et Mesures|International Conference on Weights and Measures]] redefined the meter in terms of a red cadmium spectral line (1 m = 1,553,164.13 wavelengths).<ref>{{cite journal|title = On the new determination of the meter|journal = Measurement Techniques|volume = 1|issue = 3|year = 1958|doi = 10.1007/BF00974680|pages = 259–264|first= G. D.|last = Burdun| bibcode=1958MeasT...1..259B |s2cid = 121450003}}</ref> This definition has since been changed (see [[krypton]]). At the same time, the [[International Prototype Meter]] was used as standard for the length of a meter until 1960,<ref>{{cite journal |url=https://nvlpubs.nist.gov/nistpubs/jres/104/3/j43bee.pdf |title=The NIST Length Scale Interferometer |volume=104 |issue= 3 |date=May–June 1999 |journal=Journal of Research of the National Institute of Standards and Technology |first1=John S. |last1=Beers |first2=William B. |last2=Penzes |page=226|doi=10.6028/jres.104.017 |s2cid=2981956 }}</ref> when at the [[General Conference on Weights and Measures]] the meter was defined in terms of the orange-red [[emission line]] in the [[electromagnetic spectrum]] of the [[krypton]]-86 atom in [[vacuum]].<ref name=Marion>{{cite book|last=Marion|first=Jerry B.|title=Physics For Science and Engineering|year=1982|publisher=CBS College Publishing|isbn=978-4-8337-0098-6|page=3}}</ref>

===Mercury===
[[File:Mercury symbol.svg|thumb|right|120px|The symbol for [[Mercury (planet)|the planet Mercury]] (☿) has been used since ancient times to represent the element.]]

Mercury has been found in Egyptian tombs which have been dated back to 1500 BC,<ref>{{cite web|title=Mercury and the environment&nbsp;— Basic facts|publisher=[[Environment Canada]], Federal Government of Canada|year=2004|url=http://www.ec.gc.ca/MERCURY/EN/bf.cfm|access-date=2008-03-27|url-status=dead|archive-url=https://web.archive.org/web/20070115042236/http://www.ec.gc.ca/MERCURY/EN/bf.cfm|archive-date=2007-01-15}}</ref> where mercury was used in cosmetics. It was also used by the ancient Chinese who believed it would improve and prolong health.<ref>{{cite book|title=The History of China|year=2001|author=Wright, David Curtis|publisher=Greenwood Publishing Group|isbn=978-0-313-30940-3|page=[https://archive.org/details/historyofchina00wrig/page/49 49]|url=https://archive.org/details/historyofchina00wrig/page/49}}</ref> By 500 BC mercury was used to make [[amalgam (chemistry)|amalgams]] (Medieval Latin amalgama, "alloy of mercury") with other metals.<ref>{{cite book|url=https://books.google.com/books?id=DIWEi5Hg93gC&pg=PA120|page=120|title=Jewelrymaking through history|author=Hesse, R. W.|publisher=Greenwood Publishing Group|year= 2007|isbn=978-0-313-33507-5}}</ref> [[Alchemy|Alchemists]] thought of mercury as the [[Prima materia|First Matter]] from which all metals were formed. They believed that different metals could be produced by varying the quality and quantity of [[sulfur]] contained within the mercury. The purest of these was gold, and mercury was called for in attempts at the [[wiktionary:Transmutation|transmutation]] of base (or impure) metals into gold, which was the goal of many alchemists.<ref name="Stillman">{{cite book|title = Story of Alchemy and Early Chemistry|author = Stillman, J. M.|publisher = Kessinger Publishing|year = 2003|isbn = 978-0-7661-3230-6|pages = 7–9|url = https://books.google.com/books?id=hdaAGF5Y1N0C}}{{Dead link|date=May 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

Hg is the modern [[chemical symbol]] for mercury. It comes from ''hydrargyrum'', a [[Latin]]ized form of the [[Greek language|Greek]] word Ύδραργυρος (''hydrargyros''), which is a compound word meaning "water-silver" (hydr- = water, argyros = silver)&nbsp;— since it is liquid like water and shiny like silver. The element was named after the Roman god [[Mercury (mythology)|Mercury]], known for speed and mobility. It is associated with the planet [[Mercury (planet)|Mercury]]; the astrological symbol for the planet is also one of the [[alchemical symbol]]s for the metal.<ref>{{cite book|url=https://books.google.com/books?id=ykEN2zHvCpQC&pg=PA260|page=260|title=The Pillar of Celestial Fire|author=Cox, R.|publisher=1st World Publishing|year= 1997|isbn=978-1-887472-30-2}}</ref> Mercury is the only metal for which the alchemical planetary name became the common name.<ref name="Stillman"/>

===Copernicium===
The heaviest known group 12 element, copernicium, was [[discovery of the chemical elements|first created]] on February 9, 1996, at the [[Gesellschaft für Schwerionenforschung]] (GSI) in [[Darmstadt]], Germany, by Sigurd Hofmann, [[Victor Ninov]] et al.<ref name="Hoffman">{{Cite journal|title=The new element 112 |journal=[[Zeitschrift für Physik A]]|author=Hofmann, S.|volume=354|issue=1|year=1996|pages=229–230 |doi=10.1007/BF02769517 |display-authors=etal |bibcode=1996ZPhyA.354..229H|s2cid=119975957}}</ref> It was then officially named by the [[International Union of Pure and Applied Chemistry]] (IUPAC) after [[Nicolaus Copernicus]] on February 19, 2010, the 537th anniversary of Copernicus' birth.<ref>{{cite journal |title=Element 112 is Named Copernicium |doi=10.1351/PAC-REP-08-03-05 |last1=Barber |first1=Robert C. |last2=Gäggeler |first2=Heinz W. |last3=Karol |first3=Paul J. |last4=Nakahara |first4=Hiromichi |last5=Vardaci |first5=Emanuele |last6=Vogt |first6=Erich |journal=Pure and Applied Chemistry |volume=81 |issue=7 |pages=1331–1343 |year=2009 |doi-access=free }}</ref>

==Occurrence==
Like in most other [[d-block]] groups, the [[Abundance of elements in Earth's crust|abundance in Earth's crust]] of group 12 elements decreases with higher atomic number. Zinc is with 65 [[parts per million]] (ppm) the most abundant in the group while cadmium with 0.1 ppm and mercury with 0.08 ppm are orders of magnitude less abundant.<ref>{{cite journal | doi = 10.1016/0016-7037(95)00038-2 | title = The composition of the continental crust | year = 1995 | last1 = Wedepohl | first1 = K. Hans | journal = Geochimica et Cosmochimica Acta | volume = 59 | issue = 7 | pages = 1217–1232|bibcode = 1995GeCoA..59.1217W }}</ref> Copernicium, as a synthetic element with a [[half-life]] of a few minutes, may only be present in the laboratories where it was produced.
[[File:Sphalerite4.jpg|thumb|left|upright|[[Sphalerite]] (ZnS), an important zinc ore|alt=A black shiny lump of solid with uneven surface.]]

Group 12 metals are [[Goldschmidt classification#Chalcophile elements|chalcophiles]], meaning the elements have low affinities for [[oxide]]s and prefer to bond with [[sulfide]]s. Chalcophiles formed as the crust solidified under the [[redox|reducing]] conditions of the early Earth's atmosphere.{{sfn|Greenwood|Earnshaw|1997|p=1202}} The commercially most important minerals of group 12 elements are sulfide minerals.<ref name = "chemyst"/> [[Sphalerite]], which is a form of zinc sulfide, is the most heavily mined zinc-containing ore because its concentrate contains 60–62% zinc.{{sfn|Lehto|1968|p=826}} No significant deposits of cadmium-containing ores are known. [[Greenockite]] (CdS), the only cadmium [[mineral]] of importance, is nearly always associated with sphalerite (ZnS). This association is caused by the geochemical similarity between zinc and cadmium which makes geological separation unlikely. As a consequence, cadmium is produced mainly as a byproduct from mining, smelting, and refining sulfidic ores of zinc, and, to a lesser degree, [[lead]] and [[copper]].<ref name="price">{{cite web |title=Annual Average Cadmium Price |url=http://minerals.usgs.gov/minerals/pubs/commodity/cadmium/140798.pdf |first=Jozef |last=Plachy |publisher=USGS |access-date=June 16, 2010}}</ref><ref name="lifecycle">{{cite journal |doi=10.1016/j.rser.2003.12.001 |title=Life cycle impact analysis of cadmium in CdTe PV production |year=2004 |last1=Fthenakis |first1=V. |journal=Renewable and Sustainable Energy Reviews |volume=8 |pages=303–334 |issue=4 |bibcode=2004RSERv...8..303F |url=https://zenodo.org/record/1259335}}</ref> One place where metallic cadmium can be found is the [[Vilyuy River]] basin in [[Siberia]].<ref>{{cite journal|title=New Mineral Names |first=Michael|last=Fleischer|journal=American Mineralogist|year=1980|volume=65|pages=1065–1070 |url=http://www.minsocam.org/ammin/AM65/AM65_1065.pdf}}</ref> Although mercury is an extremely rare element in the Earth's [[Crust (geology)|crust]],<ref>{{cite book|title=Geomicrobiology|author1=Ehrlich, H. L. |author2=Newman D. K. |publisher=CRC Press|year=2008|isbn=978-0-8493-7906-2 |url=https://books.google.com/books?id=GerdDmwMTLkC&pg=PA265 |page=265}}</ref> because it does not blend [[geochemistry|geochemically]] with those elements that constitute the majority of the crustal mass, mercury ores can be highly concentrated considering the element's abundance in ordinary rock. The richest mercury ores contain up to 2.5% mercury by mass, and even the leanest concentrated deposits are at least 0.1% mercury (12,000 times average crustal abundance). It is found either as a native metal (rare) or in [[cinnabar]] (HgS), [[corderoite]], [[livingstonite]] and other [[mineral]]s, with cinnabar being the most common ore.<ref>{{cite journal|doi = 10.1007/s00254-002-0629-5|title=Mercury from mineral deposits and potential environmental impact |journal=Environmental Geology|volume=43|issue=3|pages=326–338|author=Rytuba, James J|year=2003|bibcode=2003EnGeo..43..326R |s2cid=127179672 }}</ref>

While mercury and zinc minerals are found in large enough quantities to be mined, cadmium is too similar to zinc and therefore is always present in small quantities in zinc ores from where it is recovered. Identified world zinc resources total about 1.9 billion [[tonne]]s.<ref name=USGSMCS2009>{{cite web |last=Tolcin|first=A. C.|year=2011|url=http://minerals.usgs.gov/minerals/pubs/commodity/zinc/mcs-2011-zinc.pdf |publisher=[[United States Geological Survey]]|access-date=2011-06-06|title=Mineral Commodity Summaries 2009: Zinc}}</ref> Large deposits are in Australia, Canada and the United States with the largest reserves in [[Iran]].{{sfn|Greenwood|Earnshaw|1997|p=1202}}<ref>{{cite web|title=Country Partnership Strategy—Iran: 2011–12|publisher=ECO Trade and development bank |url=http://www.etdb.org/StrategiesAndResearch/Countries/CSPReports/ReportsLibrary/CPS%20Report%20-%20Islamic%20Republic%20of%20Iran.doc |access-date=2011-06-06 |url-status=dead |archive-url=https://web.archive.org/web/20111026135641/http://www.etdb.org/StrategiesAndResearch/Countries/CSPReports/ReportsLibrary/CPS%20Report%20-%20Islamic%20Republic%20of%20Iran.doc |archive-date=2011-10-26}}</ref><ref>{{cite web|url=http://www.iranconmin.de/en/leftnavigation/market|title=IRAN – a growing market with enormous potential|access-date=2010-03-03|publisher=IMRG|date=July 5, 2010|archive-date=2013-02-17|archive-url=https://web.archive.org/web/20130217181730/http://www.iranconmin.de/en/leftnavigation/market|url-status=dead}}</ref> At the current rate of consumption, these reserves are estimated to be depleted sometime between 2027 and 2055.<ref>{{Cite journal |title=Earth audit|first=David|last=Cohen|journal=New Scientist|year=2007|volume=194|issue=2605|page=8 |doi=10.1016/S0262-4079(07)61315-3}}</ref><ref>{{cite web|title=Augsberg University Calculate When Our Materials Run Out |url=http://www.idtechex.com/products/en/articles/00000591.asp|date=2007-06-04 |publisher=IDTechEx|access-date=2008-12-09}}</ref> About 346 million tonnes have been extracted throughout history to 2002, and one estimate found that about 109 million tonnes of that remains in use.<ref>{{Cite journal|last1=Gordon|first1=R. B.|last2=Bertram|first2=M.|last3=Graedel|first3=T. E.|title=Metal stocks and sustainability|journal=Proceedings of the National Academy of Sciences|volume=103|year=2006|pmid=16432205 |pmc=1360560|doi=10.1073/pnas.0509498103|issue=5|bibcode=2006PNAS..103.1209G|pages=1209–14|doi-access=free}}</ref> In 2005, China was the top producer of mercury with almost two-thirds global share followed by [[Kyrgyzstan]].<ref>{{cite report|title=World Mineral Production|publisher=British Geological Survey, NERC|location=London |year=2007}}</ref> Several other countries are believed to have unrecorded production of mercury from copper [[electrowinning]] processes and by recovery from effluents. Because of the high toxicity of mercury, both the mining of cinnabar and refining for mercury are hazardous and historic causes of mercury poisoning.<ref>[http://act.credoaction.com/campaign/thanks_mercury/?rc=fb_share1 About the Mercury Rule] {{webarchive|url= https://web.archive.org/web/20120501171523/http://act.credoaction.com/campaign/thanks_mercury/?rc=fb_share1 |date=2012-05-01}}</ref>

==Production==
Zinc is the fourth most common metal in use, trailing only [[iron]], [[aluminium]], and [[copper]] with an annual production of about 10 million tonnes.<ref name="ZincUSGS2006">{{Cite journal |url=http://minerals.usgs.gov/minerals/pubs/commodity/zinc/myb1-2006-zinc.pdf|page=Table 15|title=Zinc: World Mine Production (zinc content of concentrate) by Country|journal=2006 Minerals Yearbook: Zinc|date=February 2008|access-date=2009-01-19 }}</ref> Worldwide, 95% of the zinc is mined from [[sulfide|sulfidic]] ore deposits, in which sphalerite (ZnS) is nearly always mixed with the sulfides of copper, lead and iron. Zinc metal is produced using [[extractive metallurgy]].<ref name="Rosenqvist1922">{{Cite book|title=Principles of Extractive Metallurgy|last=Rosenqvist|first=Terkel|pages=7, 16, 186|edition=2|year=1922|isbn=978-82-519-1922-7|publisher=Tapir Academic Press}}</ref><!-- page 7 --> [[Roasting (metallurgy)|Roasting]] converts the zinc sulfide concentrate produced during processing to zinc oxide.<ref name="Zinchand">{{Cite book|url=https://books.google.com/books?id=laACw9i0D_wC|title=Zinc Handbook|first=Frank C.|last=Porter|publisher=CRC Press|year=1991|isbn=978-0-8247-8340-2}}</ref> For further processing two basic methods are used: [[pyrometallurgy]] or [[electrowinning]]. Pyrometallurgy processing reduces zinc oxide with [[carbon]] or [[carbon monoxide]] at {{convert|950|C|F|abbr=on}} into the metal, which is distilled as zinc vapor.<ref>{{Cite book|last=Bodsworth|first=Colin|title=The Extraction and Refining of Metals|page=148|year=1994|isbn=978-0-8493-4433-6|publisher=CRC Press}}</ref> The zinc vapor is collected in a condenser.<ref name="Zinchand"/> Electrowinning processing leaches zinc from the ore concentrate by [[sulfuric acid]].<ref>{{Cite book|title=Hydrometallurgy in Extraction Processes|last1=Gupta|first1=C. K.|last2=Mukherjee|first2=T. K.|page=62|publisher=CRC Press|isbn=978-0-8493-6804-2|year=1990}}</ref> After this step [[electrolysis]] is used to produce zinc metal.<ref name="Zinchand"/>

Cadmium is a common impurity in zinc ores, and it is most isolated during the production of zinc. Some zinc ores concentrates from sulfidic zinc ores contain up to 1.4% of cadmium.<ref name="Cd-Trend">{{cite book|url = https://books.google.com/books?id=okArAAAAYAAJ| title = Trends in Usage of Cadmium: Report|publisher = National Research Council, National Academy of Sciences-National Academy of Engineering|author = ((National Research Council, Panel on Cadmium, Committee on Technical Aspects of Critical and Strategic Material))|year = 1969|pages = 1–3}}</ref>  Cadmium is isolated from the zinc produced from the flue dust by [[vacuum distillation]] if the zinc is smelted, or cadmium sulfate is [[precipitate]]d out of the electrolysis solution.<ref>{{cite book | url = https://books.google.com/books?id=9yzN-QGag_8C&pg=PA104 | pages= 104–116 | title = Mercury, cadmium, lead: handbook for sustainable heavy metals policy and regulation | isbn = 978-1-4020-0224-3 | author1 = Scoullos, Michael J | date = 2001-12-31| publisher= Springer }}</ref>

The richest mercury ores contain up to 2.5% mercury by mass, and even the leanest concentrated deposits are at least 0.1% mercury, with cinnabar (HgS) being the most common ore in the deposits.<ref>{{cite journal |doi= 10.1007/s00254-002-0629-5|title=Mercury from mineral deposits and potential environmental impact |author=Rytuba, James J. |journal=Environmental Geology|volume=43|issue=3|pages=326–338|year=2003|bibcode=2003EnGeo..43..326R |s2cid=127179672 }}</ref>
Mercury is extracted by heating cinnabar in a current of air and condensing the vapor.<ref>{{cite book |url=https://books.google.com/books?id=4AV2Wds_NZAC&pg=PA865 |pages=865–866 |title=Fundamentals of air pollution |isbn=978-0-12-373615-4 |author1=Vallero, Daniel A. |year=2008|publisher=Elsevier }}</ref>

[[Superheavy element]]s such as copernicium are produced by bombarding lighter elements in [[particle accelerator]]s that induces [[fusion reaction]]s. Whereas most of the isotopes of copernicium can be synthesized directly this way, some heavier ones have only been observed as decay products of elements with higher [[atomic number]]s.<ref name=fusion>{{cite journal|last1=Barber|first1=Robert C.| last2=Gäggeler| first2=Heinz W.| last3=Karol| first3=Paul J.| last4=Nakahara| first4=Hiromichi| last5=Vardaci|  first5=Emanuele|last6=Vogt| first6=Erich|title=Discovery of the element with atomic number 112 (IUPAC Technical Report)|journal=Pure and Applied Chemistry| volume=81| issue=7| page=1331| year=2009| doi=10.1351/PAC-REP-08-03-05|s2cid=95703833|url=http://doc.rero.ch/record/297412/files/pac-rep-08-03-05.pdf}}</ref> The first fusion reaction to produce copernicium was performed by GSI in 1996, who reported the detection of two decay chains of copernicium-277 (though one was later retracted, as it had been based on data fabricated by [[Victor Ninov]]):<ref name="Hoffman"/>

:{{nuclide|link=yes|lead|208}} + {{nuclide|link=yes|zinc|70}} → {{nuclide|copernicium|277}} + {{SubatomicParticle|link=yes|Neutron}}

==Applications==
Due to the physical similarities which they share, the group 12 elements can be found in many common situations. Zinc and cadmium are commonly used as [[anti-corrosion]] (galvanization) agents{{sfn|Greenwood|Earnshaw|1997|p=}} as they will attract all local [[oxidation]] until they completely corrode.{{sfn|Stwertka|1998|p={{pn|date=June 2020}}}} These protective coatings can be applied to other metals by [[hot-dip galvanizing]] a substance into the molten form of the metal,{{sfn|Emsley|2001|pp=499–505}} or through the process of [[electroplating]] which may be [[Passivation (chemistry)|passivated]] by the use of [[Monochromate|chromate]] salts.<ref name="fff"/> Group 12 elements are also used in [[electrochemistry]] as they may act as an alternative to the [[standard hydrogen electrode]] in addition to being a secondary reference electrode.<ref>{{cite book |title=Electrochemical Systems |last=Newman |first=John |year=2004 |publisher=John Wiley & Sons |location=New Jersey |isbn=978-0-471-47756-3 }}</ref>

In the US, zinc is used predominantly for [[Galvanization|galvanizing]] (55%) and for [[brass]], [[bronze]] and other alloys (37%).<ref name="USGS-yb2006">{{cite web|title=Zinc: World Mine Production (zinc content of concentrate) by Country |url=http://minerals.usgs.gov/minerals/pubs/commodity/zinc/myb1-2009-zinc.pdf |work=2009 Minerals Yearbook: Zinc|publisher=United States Geological Survey|location=Washington, D.C. |date=February 2010|access-date=2010-06-06}}</ref>  The relative reactivity of zinc and its ability to attract oxidation to itself makes it an efficient [[sacrificial anode]] in [[cathodic protection]] (CP). For example, cathodic protection of a buried pipeline can be achieved by connecting anodes made from zinc to the pipe.{{sfn|Lehto|1968|p=829}} Zinc acts as the [[anode]] (negative terminus) by slowly corroding away as it passes electric current to the steel pipeline.{{sfn|Lehto|1968|p=829}}<ref group=note>Electric current will naturally flow between zinc and steel but in some circumstances inert anodes are used with an external DC source.</ref> Zinc is used to cathodically protect metals that are exposed to sea water from corrosion.<ref>{{Cite journal|title=A comparative study of the electrochemical behaviour of Algerian zinc and a zinc from a commercial sacrificial anode|first1=M.|last1=Bounoughaz |last2=Salhi |first2=E.|last3=Benzine |first3=K.|last4=Ghali|first4=E.|last5=Dalard|first5=F.|year=2003 |journal=Journal of Materials Science|volume=38|issue=6|pages=1139–1145 |doi=10.1023/A:1022824813564|bibcode=2003JMatS..38.1139B|s2cid=135744939}}</ref>{{sfn|Stwertka|1998|p=99}}
Zinc is used as an anode material for batteries such as in [[zinc–carbon battery|zinc–carbon batteries]]<ref>{{Cite book|first=Jürgen O.|last=Besenhard|title=Handbook of Battery Materials|access-date=2008-10-08 |publisher=Wiley-VCH|url=http://www.ulb.tu-darmstadt.de/tocs/60178752.pdf|isbn=978-3-527-29469-5|year=1999|bibcode=1999hbm..book.....B}}</ref><ref>{{Cite journal|doi=10.1016/0378-7753(95)02242-2|year=1995|title=Recycling zinc batteries: an economical challenge in consumer waste management|first1=J.-P.|last1=Wiaux|last2=Waefler|first2=J.-P.|journal=Journal of Power Sources|volume=57|issue=1–2|pages=61–65|bibcode=1995JPS....57...61W}}</ref> or [[zinc–air battery]]/fuel cells.<ref>{{Cite book|last=Culter|first=T.|title=Southcon/96 Conference Record |chapter=A design guide for rechargeable zinc-air battery technology |doi=10.1109/SOUTHC.1996.535134 |isbn=978-0-7803-3268-3 |year=1996 |page=616|s2cid=106826667}}</ref><ref>{{cite web |url=http://www.electric-fuel.com/evtech/papers/paper11-1-98.pdf |title=Zinc Air Battery-Battery Hybrid for Powering Electric Scooters and Electric Buses|first1=Jonathan|last1=Whartman|last2=Brown |first2=Ian |publisher=The 15th International Electric Vehicle Symposium|access-date=2008-10-08|url-status=dead|archive-url=https://web.archive.org/web/20060312003601/http://www.electric-fuel.com/evtech/papers/paper11-1-98.pdf |archive-date=2006-03-12}}</ref><ref>{{cite journal|title=A refuelable zinc/air battery for fleet electric vehicle propulsion|journal=NASA Sti/Recon Technical Report N|volume=96|pages=11394|last1=Cooper|first1=J. F. |last2=Fleming |first2=D.|last3=Hargrove|first3=D.|last4=Koopman|last5=R.|last6=Peterman|first6=K. |publisher=Society of Automotive Engineers future transportation technology conference and exposition |osti=82465|bibcode=1995STIN...9611394C |year=1995}}</ref>
A widely used alloy which contains zinc is brass, in which copper is alloyed with anywhere from 3% to 45% zinc, depending upon the type of brass.{{sfn|Lehto|1968|p=829}} Brass is generally more [[ductile]] and stronger than copper and has superior [[corrosion resistance]].{{sfn|Lehto|1968|p=829}} These properties make it useful in communication equipment, hardware, musical instruments, and water valves.{{sfn|Lehto|1968|p=829}} Other widely used alloys that contain zinc include [[nickel silver]], typewriter metal, soft and aluminium [[solder]], and commercial [[bronze]].<ref name="CRCp4-41"/> Alloys of primarily zinc with small amounts of copper, aluminium, and magnesium are useful in [[die casting]] as well as [[spin casting]], especially in the automotive, electrical, and hardware industries.<ref name="CRCp4-41"/> These alloys are marketed under the name [[Zamak]].<ref>{{cite web |url=http://www.eazall.com/diecastalloys.aspx |title=Diecasting Alloys|publisher=Eastern Alloys|access-date=2009-01-19|location=Maybrook, NY}}</ref> Roughly one quarter of all zinc output in the United States (2009) is consumed in the form of zinc compounds, a variety of which are used industrially.<ref name="USGS-yb2006"/>

Cadmium has many common industrial uses as it is a key component in battery production, is present in [[cadmium pigments]],<ref name="colors">{{cite book|last1=Buxbaum|first1=Gunter|last2=Pfaff|first2=Gerhard|chapter=Cadmium Pigments|chapter-url=https://books.google.com/books?id=_OrB0ew_HgAC&pg=PA121|pages=121–123|isbn=978-3-527-30363-2|publisher=Wiley-VCH|year=2005|title=Industrial inorganic pigments}}{{Dead link|date=May 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> coatings,<ref name="fff">{{cite web |url=http://ftp.rta.nato.int/public//PubFulltext/RTO/MP/RTO-MP-025///MP-025-15.pdf |title=Advances to Protective Coatings and their Application to Ageing Aircraft |author1=Smith, C.J.E. |author2=Higgs, M.S. |author3=Baldwin, K.R. |date=April 20, 1999 |publisher=RTO MP-25 |access-date=May 29, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20160304105705/http://ftp.rta.nato.int/public//PubFulltext/RTO/MP/RTO-MP-025///MP-025-15.pdf |archive-date=March 4, 2016 }}</ref> and is commonly used in electroplating.<ref name="HgCdPb"/> In 2009, 86% of cadmium was used in [[Battery (electricity)|batteries]], predominantly in [[rechargeable battery|rechargeable]] [[nickel-cadmium battery|nickel-cadmium batteries]]. The European Union banned the use of cadmium in electronics in 2004 with several exceptions but reduced the allowed content of cadmium in electronics to 0.002%.<ref>{{cite web |title=Battery collection; recycling, nature protected|publisher=[[European Union]] |url=http://www.europarl.europa.eu/sides/getDoc.do?pubRef=-//EP//TEXT+IM-PRESS+20060628BRI09328+FULL-TEXT+DOC+XML+V0//EN|access-date=November 4, 2008}}</ref> Cadmium [[electroplating]], consuming 6% of the global production,  can be found in the aircraft industry due to the ability to resist [[corrosion]] when applied to steel components.<ref name="HgCdPb">{{cite book |url=https://books.google.com/books?id=9yzN-QGag_8C|title=Mercury, Cadmium, Lead: Handbook for Sustainable Heavy Metals Policy and Regulation|first1=Michael J.|last1=Scoullos|last2=Vonkeman|first2=Gerrit H.|last3=Thornton |first3=Iain |last4=Makuch|first4=Zen|publisher=Springer|year=2001|isbn=978-1-4020-0224-3}}</ref>

Mercury is used primarily for the manufacture of industrial chemicals or for electrical and electronic applications. It is used in some thermometers, especially ones which are used to measure high temperatures. A still increasing amount is used as gaseous mercury in [[fluorescent lamps]],<ref>{{cite book|title = A guide to the use and calibration of detector array equipment|author1=Hopkinson, G. R. |author2=Goodman, T. M. |author3=Prince, S. R. | publisher = SPIE Press| year = 2004| page = 125| isbn = 978-0-8194-5532-1|bibcode=2004gucd.book.....H }}</ref>  while most of the other applications are slowly phased out due to health and safety regulations,<ref>{{cite news| title = Mercury Reduction Act of 2003|url =https://openlibrary.org/b/OL17617678M|access-date = 2009-06-06| publisher = United States. Congress. Senate. Committee on Environment and Public Works}}</ref> and is in some applications replaced with less toxic but considerably more expensive [[Galinstan]] alloy.<ref>{{cite journal|doi=10.1007/s00216-005-0069-7|date=Nov 2005|author1=Surmann, P. |author2=Zeyat, H. |title=Voltammetric analysis using a self-renewable non-mercury electrode|volume=383|issue=6|pages=1009–13|pmid=16228199|journal=Analytical and Bioanalytical Chemistry|s2cid=22732411}}</ref> Mercury and its compounds have been used in medicine, although they are much less common today than they once were, now that the toxic effects of mercury and its compounds are more widely understood.<ref>{{cite web|author = FDA|url =https://www.fda.gov/Cber/vaccine/thimerosal.htm|archive-url =https://web.archive.org/web/20011030175538/http://www.fda.gov/cber/vaccine/thimerosal.htm|url-status =dead|archive-date =October 30, 2001|title = Thimerosal in Vaccines|website =[[Food and Drug Administration]]|access-date=October 25, 2006}}</ref> It is still used as an ingredient in [[amalgam (dentistry)|dental amalgams]]. In the late 20th century the largest use of mercury<ref>{{cite journal|title=The CRB Commodity Yearbook (annual)|journal= The CRB Commodity Yearbook|year= 2000|page=173|issn=1076-2906}}</ref><ref name="USEPA">{{cite web|url=http://www.epa.gov/nrmrl/pubs/600r02104/600r02104chap3.pdf|author=Leopold, B. R.|year=2002|title=Chapter 3: Manufacturing Processes Involving Mercury. ''Use and Release of Mercury in the United States''|publisher=National Risk Management Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, Ohio|access-date=May 1, 2007 |archive-url =https://web.archive.org/web/20070621093346/http://www.epa.gov/nrmrl/pubs/600r02104/600r02104chap3.pdf |archive-date = June 21, 2007}}</ref> was in the mercury cell process (also called the [[Castner-Kellner process]]) in the production of [[chlorine]] and [[caustic soda]].<ref>{{cite web|url=http://www.eurochlor.org/animations/mercury-cell.asp |title=Chlorine Online Diagram of mercury cell process |publisher=Euro Chlor |access-date=2012-04-09 |url-status=dead |archive-url=https://web.archive.org/web/20110918011944/http://www.eurochlor.org/animations/mercury-cell.asp |archive-date=September 18, 2011 }}</ref>

Copernicium has no use other than research due to its very high radioactivity.

==Biological role and toxicity==
The group 12 elements have multiple effects on biological organisms as cadmium and mercury are toxic while zinc is required by most plants and animals in trace amounts.

Zinc is an essential [[trace element]], necessary for plants,<ref name=Broadley2007>{{cite journal|last1=Broadley|first1=M. R.|last2=White|first2=P. J.|last3=Hammond|first3=J. P.|last4=Zelko|first4=I.|last5=Lux|first5=A.|title=Zinc in plants|journal=New Phytologist|volume=173|year=2007|pmid=17286818|doi=10.1111/j.1469-8137.2007.01996.x|issue=4|pages=677–702|doi-access=free}}</ref> animals,<ref>{{cite journal|author=Prasad A. S.|title=Zinc in Human Health: Effect of Zinc on Immune Cells|journal=Mol. Med.|volume=14|year=2008|pmid=18385818|pmc=2277319|doi=10.2119/2008-00033.Prasad|issue=5–6|pages=353–7}}</ref> and [[microorganism]]s.<ref>Zinc's role in microorganisms is particularly reviewed in: {{cite journal|author=Sugarman, B.|title=Zinc and infection|journal=Reviews of Infectious Diseases|volume=5|year=1983|pmid=6338570|issue=1|pages=137–47|doi=10.1093/clinids/5.1.137}}</ref> It is "typically the second most abundant transition metal in organisms" after [[iron]] and it is the only metal which appears in all [[Enzyme#Naming conventions|enzyme classes]].<ref name=Broadley2007/> There are 2–4&nbsp;grams of zinc<ref name=Rink2000>{{cite journal|last1=Rink|first1 =L.|last2=Gabriel|first2=P.|title=Zinc and the immune system|journal=Proc Nutr Soc|volume=59|year=2000|pmid=11115789|doi=10.1017/S0029665100000781|issue=4|pages=541–52|doi-access=free}}</ref> distributed throughout the human body,<ref>{{cite book|last=Wapnir|first=Raul A.|title=Protein Nutrition and Mineral Absorption|publisher=CRC Press|location=Boca Raton, Florida|year=1990|isbn=978-0-8493-5227-0|url=https://books.google.com/books?id=qfKdaCoZS18C}}</ref><!-- page 131 --> and it plays "ubiquitous biological roles".<ref name=Hambridge2007>{{Cite journal|author1=Hambidge, K. M.|author2=Krebs, N. F.|title=Zinc deficiency: a special challenge|journal=J. Nutr.|volume=137|year=2007|pmid=17374687|issue=4|pages=1101–5|doi=10.1093/jn/137.4.1101|doi-access=free}}</ref> A 2006 study estimated that about 10% of human proteins (2800) potentially bind zinc, in addition to hundreds which transport and traffic zinc.<ref name=Broadley2007/> In the U.S., the [[Recommended Dietary Allowance]] (RDA) is 8&nbsp;mg/day for women and 11&nbsp;mg/day for men.<ref name=rda>{{cite book|author1=Connie W. Bales|author2=Christine Seel Ritchie|title=Handbook of Clinical Nutrition and Aging|url=https://books.google.com/books?id=jtsBbP2087wC&pg=PA151|access-date=23 June 2011|date=21 May 2009|publisher=Springer|isbn=978-1-60327-384-8|pages=151–}}</ref> Harmful excessive supplementation may be a problem and should probably not exceed 20&nbsp;mg/day in healthy people,<ref>{{Cite journal|last1 =Maret|first1=W.|last2=Sandstead|first2=H. H.|title=Zinc requirements and the risks and benefits of zinc supplementation|journal=[[Journal of Trace Elements in Medicine and Biology]]|volume=20|year=2006|pmid=16632171|doi=10.1016/j.jtemb.2006.01.006|issue =1|pages =3–18|bibcode=2006JTEMB..20....3M }}</ref> although the U.S. National Research Council set a Tolerable Upper Intake of 40&nbsp;mg/day.<ref>{{cite book|url=http://books.nap.edu/openbook.php?record_id=10026&page=442|title=Zinc – Summary|access-date=2010-03-30|publisher=[[Institute of Medicine]], Food and Nutrition Board|work=Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2001)|year=2001 |doi=10.17226/10026 |pmid=25057538 |isbn=978-0-309-07279-3 |author1=Institute of Medicine (US) Panel on Micronutrients }}</ref>

Mercury and cadmium are toxic and may cause environmental damage if they enter rivers or rain water. This may result in contaminated crops<ref>{{cite journal|title = Environmental cadmium exposure, adverse effects, and preventative measures in Japan|first1 = Koji|last1 = Nogawa|journal = Biometals|year = 2004|volume = 17|issue = 5|pages =581–587|doi = 10.1023/B:BIOM.0000045742.81440.9c|pmid = 15688869|last2 = Kobayashi|first2 = E.|last3 = Okubo|first3 = Y.|last4 = Suwazono|first4 = Y.|s2cid = 8053594}}</ref> as well as the [[bioaccumulation]] of mercury in a food chain leading to an increase in illnesses caused by [[mercury poisoning|mercury]] and [[cadmium poisoning]].<ref name="Mozaffarian D, Rimm EB 2006 1885–99">{{cite journal |journal=JAMA |year=2006 |volume=296 |issue=15 |pages=1885–99 |title= Fish intake, contaminants, and human health: evaluating the risks and the benefits |vauthors=Mozaffarian D, Rimm EB |pmid=17047219 |doi=10.1001/jama.296.15.1885|doi-access=free }}</ref>

==Notes==
<references group=note/>

==References==
{{reflist|30em}}

==Bibliography==
{{sfn whitelist |CITEREFGreenwoodEarnshaw1997}}
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|isbn=978-0-442-15598-8
|chapter=Zinc
|pages=[https://archive.org/details/encyclopediaofch00hamp/page/822 822]–830
|lccn=68-29938
}}
*<!-- Sw -->{{cite book
|title=Guide to the Elements
|url=https://archive.org/details/guidetoelements00stwe
|url-access=registration
|edition=Revised
|first=Albert
|last=Stwertka
|publisher=Oxford University Press
|year=1998
|chapter=Zinc
|isbn=978-0-19-508083-4
}}
*<!-- We -->{{cite book
|last=Weeks
|first=Mary Elvira
|author-link=Mary Elvira Weeks
|year=1933
|title=The Discovery of the Elements
|publisher=Journal of Chemical Education
|location=Easton, PA
|chapter=III. Some Eighteenth-Century Metals
|isbn=978-0-7661-3872-8
}}
{{refend}}

{{Periodic table (navbox)}}
{{Navbox periodic table}}
{{Group 12 elements}}

[[Category:Groups (periodic table)]]