Editing Group 12 element (section)

===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.