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In chemistry, the term post-transition metal is used to describe the category of metallic elements to the right of the transition elements on the periodic table. There are two IUPAC definitions of "transition element"[1] that have been in apparent conflict with one another since September 2007.
According to the first definition, transition metals are elements in group 3 through group 11. In this case, post-transition metals include all of group 12—zinc, cadmium, mercury, and ununbium.
According to the second definition, transition elements either have an incomplete d-subshell or have the ability to form an incomplete d-subshell. In 2007, mercury(IV) fluoride was synthesized.[2][3] This compound contains a mercury atom with an incomplete d-subshell, and ununbium is predicted to have the capacity to form a similar electronic configuration. In this case, post-transition metals include only zinc and cadmium within group 12. This situation is illustrated by the element boxes colored gray to the right.
Finally, there is a common non-IUPAC definition that equates transition metals with the d-block. In this case, all of group 12 would consist of transition metals. This definition is not used at the university level.[4]
Antimony (atomic number=51, placed to the right of Sn on the table) is arguably either a metalloid or a metal and is often considered to be a post-transition metal.[4] Aluminium (atomic number=13, placed above Ga) is neither a transition nor a post-transition metal because it has no d-subshell and is located above the transition elements in the table. Also, the categorization of all "Uu" elements is speculative and not based on experimental data.
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Poor metals
The trivial name poor metals is sometimes applied to the metallic elements in the p-block of the periodic table. Their melting and boiling points are generally lower than those of the transition metals and their electronegativity higher, and they are also softer. They are distinguished from the metalloids, however, by their significantly higher boiling points in the same row.
"Poor metals" is not a rigorous IUPAC-approved nomenclature, but the grouping is generally taken to include aluminium, gallium, indium, tin, thallium, lead, and bismuth. Occasionally germanium, antimony, and polonium are also included, although these are usually considered to be metalloids or "semi-metals". Elements 113 to 116, which are currently allocated the systematic names ununtrium, ununquadium, ununpentium and ununhexium, would likely exhibit properties characteristic of poor metals; however sufficient quantities of them have not yet been synthesized to examine their chemical properties.
| 13 | 14 | 15 | 16 |
|---|---|---|---|
| Al Aluminium |
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| Ga Gallium |
Ge Germanium |
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| In Indium |
Sn Tin |
Sb Antimony |
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| Tl Thallium |
Pb Lead |
Bi Bismuth |
Po Polonium |
| Uut ununtrium |
Uuq ununquadium |
Uup ununpentium |
Uuh ununhexium |
See also
References
Notes
- ^ IUPAC Provisional Recommendations for the Nomenclature of Inorganic Chemistry (2004) (online draft of an updated version of the "Red Book" IR 3-6.2)
- ^ Xuefang Wang; Lester Andrews; Sebastian Riedel; and Martin Kaupp (2007). "Mercury Is a Transition Metal: The First Experimental Evidence for HgF4.". Angew. Chem. Int. Ed. 46 (44): 8371–8375. doi:10.1002/anie.200703710
- ^ Elusive Hg(IV) species has been synthesized under cryogenic conditions (October 12, 2007) Accessed December 2, 2007
- ^ a b "Post Transition Metal Chemistry Lecture 1" WebLearn - Oxford Campus, Department of Chemistry, public anonymous access, Michaelmas Term 2007, Prof. R.G. Egdell, Accessed December 2, 2007
Bibliography
- The Chemistry Student's Companion, Stephen Schaffter, Lulu Press, Inc 2006 ISBN 1-4116-9247-0
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- This page was last modified on 23 September 2008, at 12:15.
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