Editing Group 12 element (section)

===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 || ?
|}