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{{Short description|Metals resistant to corrosion and oxidation}} |
{{Short description|Metals resistant to corrosion and oxidation}} |
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{{Use British English|date = February 2019}} |
{{Use British English|date = February 2019}} |
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In [[chemistry]], the '''noble metals''' are [[metal]]s that are resistant to [[corrosion]] and [[oxidation]] in moist air (unlike most [[base metal]]s). The short list of chemically noble metals (those elements upon which almost all [[chemist]]s agree) comprises [[ruthenium]] (Ru), [[rhodium]] (Rh), [[palladium]] (Pd), [[silver]] (Ag), [[osmium]] (Os), [[iridium]] (Ir), [[platinum]] (Pt), and [[gold]] (Au).<ref>A. Holleman, N. Wiberg, "Lehrbuch der Anorganischen Chemie", de Gruyter, 1985, 33. edition, p. 1486</ref> |
In [[chemistry]], the '''noble metals''' are [[metal]]s that are resistant to [[corrosion]] and [[oxidation]] in moist air (unlike most [[base metal]]s). In periodic table terms they correspond to the [[noble gas]]es.<ref name="HW2001"/> The short list of chemically noble metals (those elements upon which almost all [[chemist]]s agree) comprises [[ruthenium]] (Ru), [[rhodium]] (Rh), [[palladium]] (Pd), [[silver]] (Ag), [[osmium]] (Os), [[iridium]] (Ir), [[platinum]] (Pt), and [[gold]] (Au).<ref>A. Holleman, N. Wiberg, "Lehrbuch der Anorganischen Chemie", de Gruyter, 1985, 33. edition, p. 1486</ref> |
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More inclusive lists include one or more of [[mercury (element)|mercury]] (Hg),<ref>{{cite web|url=http://www.uni-protokolle.de/Lexikon/Edelmetall.html|title=Edelmetall|author=|date=|website=www.uni-protokolle.de|accessdate=6 April 2018}}</ref><ref>"Dictionary of Mining, Mineral, and Related Terms", Compiled by the American Geological Institute, 2nd edition, 1997</ref><ref>Scoullos, M.J., Vonkeman, G.H., Thornton, I., Makuch, Z., "Mercury – Cadmium – Lead: Handbook for Sustainable Heavy Metals Policy and Regulation",Series: Environment & Policy, Vol. 31, Springer-Verlag, 2002</ref> [[rhenium]] (Re),<ref>The New Encyclopædia Britannica, 15th edition, Vol. VII, 1976</ref> and [[copper]] (Cu) as noble metals. On the other hand, [[titanium]] (Ti), [[niobium]] (Nb), and [[tantalum]] (Ta) are not included as noble metals although they are very resistant to corrosion. |
More inclusive lists include one or more of [[mercury (element)|mercury]] (Hg),<ref>{{cite web|url=http://www.uni-protokolle.de/Lexikon/Edelmetall.html|title=Edelmetall|author=|date=|website=www.uni-protokolle.de|accessdate=6 April 2018}}</ref><ref>"Dictionary of Mining, Mineral, and Related Terms", Compiled by the American Geological Institute, 2nd edition, 1997</ref><ref>Scoullos, M.J., Vonkeman, G.H., Thornton, I., Makuch, Z., "Mercury – Cadmium – Lead: Handbook for Sustainable Heavy Metals Policy and Regulation",Series: Environment & Policy, Vol. 31, Springer-Verlag, 2002</ref> [[rhenium]] (Re),<ref>The New Encyclopædia Britannica, 15th edition, Vol. VII, 1976</ref> and [[copper]] (Cu) as noble metals. On the other hand, [[titanium]] (Ti), [[niobium]] (Nb), and [[tantalum]] (Ta) are not included as noble metals although they are very resistant to corrosion. |
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In physics, the definition of a noble metal is most strict. It requires that the [[atomic orbital|d-bands]] of the [[Electronic band structure|electronic structure]] be filled. From this perspective, only copper, silver and gold are noble metals, as all d-like bands are filled and do not cross the [[Fermi level]].<ref>{{cite journal | doi = 10.1209/epl/i2005-10075-5 | title = Making a noble metal of Pd | year = 2005 |author1=Hüger, E. |author2=Osuch, K. | journal = EPL | volume = 71 | pages = 276|bibcode = 2005EL.....71..276H | issue = 2 }}</ref> However, d-hybridized bands do cross the Fermi level to a small extent. In the case of platinum, two d bands cross the Fermi level, changing its chemical behaviour such that it can function as a [[Catalysis|catalyst]]. The difference in reactivity can easily be seen during the preparation of clean metal surfaces in an [[ultra-high vacuum]]: surfaces of "physically defined" noble metals (e.g., gold) are easy to clean and keep clean for a long time, while those of platinum or palladium, for example, are covered by [[carbon monoxide]] very quickly.<ref>S. Fuchs, T.Hahn, H.G. Lintz, "The oxidation of carbon monoxide by oxygen over platinum, palladium and rhodium catalysts from 10<sup>−10</sup> to 1 bar", Chemical engineering and processing, 1994, V 33(5), pp. 363–369 [http://cat.inist.fr/?aModele=afficheN&cpsidt=3322977]</ref> |
In physics, the definition of a noble metal is most strict. It requires that the [[atomic orbital|d-bands]] of the [[Electronic band structure|electronic structure]] be filled. From this perspective, only copper, silver and gold are noble metals, as all d-like bands are filled and do not cross the [[Fermi level]].<ref>{{cite journal | doi = 10.1209/epl/i2005-10075-5 | title = Making a noble metal of Pd | year = 2005 |author1=Hüger, E. |author2=Osuch, K. | journal = EPL | volume = 71 | pages = 276|bibcode = 2005EL.....71..276H | issue = 2 }}</ref> However, d-hybridized bands do cross the Fermi level to a small extent. In the case of platinum, two d bands cross the Fermi level, changing its chemical behaviour such that it can function as a [[Catalysis|catalyst]]. The difference in reactivity can easily be seen during the preparation of clean metal surfaces in an [[ultra-high vacuum]]: surfaces of "physically defined" noble metals (e.g., gold) are easy to clean and keep clean for a long time, while those of platinum or palladium, for example, are covered by [[carbon monoxide]] very quickly.<ref>S. Fuchs, T.Hahn, H.G. Lintz, "The oxidation of carbon monoxide by oxygen over platinum, palladium and rhodium catalysts from 10<sup>−10</sup> to 1 bar", Chemical engineering and processing, 1994, V 33(5), pp. 363–369 [http://cat.inist.fr/?aModele=afficheN&cpsidt=3322977]</ref> |
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== |
== Electrochemistry == |
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The following table lists [[standard reduction potential]] in volts;<ref>G. Wulfsberg, "Inorganic Chemistry", University Science Books, 2000, pp. 247–249 ✦ Bratsch S. G., "Standard Electrode Potentials and Temperature Coefficients in Water at 298.15 K", ''Journal of Physical Chemical Reference Data,'' vol. 18, no. 1, 1989, pp. 1–21 ✦ B. Douglas, D. McDaniel, J. Alexander, "Concepts and Models of Inorganic Chemistry", John Wiley & Sons, 1994, p. E-3</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| last1=Hoffman|first1=Darleane C. |last2=Lee |first2=Diana M. |last3=Pershina |first3=Valeria |chapter=Transactinides and the future elements| publisher= [[Springer Science+Business Media]]| year=2006| isbn=1-4020-3555-1| location=Dordrecht, The Netherlands| edition=3rd| ref=CITEREFHaire2006}}</ref>; electronegativity (revised Pauling); and electron affinity values (kJ/mol), for some metals and metalloids. Metals commonly recognised as noble metals are flagged with a ✣ symbol; elements marked  ☢ are synthetic, radioactive, and short-lived; metalloids are denoted <sup><small>MD</small></sup>; values with a † are predicted; a blank na = not available or applicable. |
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{| class="wikitable sortable" |
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⚫ | The [[superheavy element]]s from [[hassium]] to [[livermorium]] inclusive are expected to be "partially very noble metals"; chemical investigations of hassium has established that it behaves like its lighter congener osmium, and preliminary investigations of [[nihonium]] and [[flerovium]] have suggested but not definitively established noble behavior.<ref>{{cite journal | |
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!Element !! Atomic<br>number !! Group !! Period !! Reaction !! Poten-<br>tial (V) || Electro-<br>negativity||Electron<br>affinity||Note |
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|| [[Copernicium]] ☢ || 112 || 12 || 7 || {{chem|Cn|2+}} + 2 e<sup>−</sup> → Cn || 2.1|| || ||† |
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|| [[Roentgenium]] ☢ || 111 || 11 || 7 || {{chem|Rg|3+}} + 3 e<sup>−</sup> → Rg || 1.9|| || ||† |
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|| [[Darmstadtium]] ☢ || 110 || 10 || 7 || {{chem|Ds|2+}} + 2 e<sup>−</sup> → Ds || 1.7|| || ||† |
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|| [[Gold]] ✣ || 79 || 11 || 6 || {{chem|Au|3+}} + 3 e<sup>−</sup> → Au || 1.5 ||2.54|| 223 || |
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|| [[Platinum]] ✣ || 78 || 10 || 6 || {{chem|Pt|2+}} + 2 e<sup>−</sup> → Pt || 1.2 ||2.28|| 205 || |
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|| [[Iridium]] ✣ || 77 || 9 || 6 || {{chem|Ir|3+}} + 3 e<sup>−</sup> → Ir || 1.16 ||2.2|| 151 || |
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|| [[Astatine]] ☢ || 85 || 17 || 6 || {{chem|At|+}} + e<sup>−</sup> → At || 1.0 ||2.2|| 233 || |
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|| [[Palladium]] ✣ || 46 || 10 || 5 || {{chem|Pd|2+}} + 2 e<sup>−</sup> → Pd || 0.915 ||2.2|| 54 || |
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|| [[Flerovium]] ☢ || 114 || 14 || 7 || {{chem|Fl|2+}} + 2 e<sup>−</sup> → Fl || 0.9  ||2.21 || ||† |
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|| [[Osmium]] ✣ || 76 || 8 || 6 || {{chem|OsO|2}} + 4 {{chem|H|+}} + 4 e<sup>−</sup> → Os + 2 {{chem|H|2|O}} || 0.85 ||2.2|| 104 || |
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|| [[Mercury (element)|Mercury]] || 80 || 12 || 6 || {{chem|Hg|2+}} + 2 e<sup>−</sup> → Hg || 0.85 ||2.0|| −50 || |
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|| [[Rhodium]] ✣ || 45 || 9 || 5 || {{chem|Rh|3+}} + 3 e<sup>−</sup> → Rh || 0.8 ||2.28|| 110 || |
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|| [[Meitnerium]] ☢ || 109 || 9 || 7 || {{chem|Mt|3+}} + 3 e<sup>−</sup> → Mt || 0.8  || || ||† |
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|| [[Silver]] ✣ || 47 || 11 || 5 || {{chem|Ag|+}} + e<sup>−</sup> → Ag || 0.7993 ||1.93|| 126 || |
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|| [[Ruthenium]] ✣ || 44 || 8 || 5 || {{chem|Ru|3+}} + 3 e<sup>−</sup> → Ru || 0.6 ||2.2|| 101 || |
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|| [[Polonium]] ☢ || 84 || 16 || 6 || {{chem|Po|2+}} + 2 e<sup>−</sup> → Po || 0.6 ||2.0|| 136 || |
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|| [[Nihonium]] ☢ || 113 || 13 || 7 || {{chem|Nh|+}} + e<sup>−</sup> → Nh || 0.6 †||2.09 || ||† |
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|| [[Tellurium]] <sup><small>MD</small></sup> || 52 || 16 || 5 || {{chem|Te|O|2}} + 4 {{chem|H|+}} + 4 e<sup>−</sup> → Te + 2 {{chem|H|2|O}} || 0.53 ||2.1|| 190|| |
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|| [[Rhenium]] || 75 || 7 || 6 || {{chem|Re|3+}} + 3 e<sup>−</sup> → Re || 0.5 ||1.9 || 6 || |
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|- style="background:orange" |
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|| Water || 75 || 7 || 6 || {{chem|H|2|O}} + 4 e<sup>−</sup> +{{chem|O|2}} → 4 OH<sup>−</sup> || 0.4 || || || |
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|| [[Hassium]] ☢ || 108 || 8 || 7 || {{chem|Hs|4+}} + 4 e<sup>−</sup> → Hs || 0.4 || || ||† |
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|| [[Copper]] || 29 || 11 || 4 || {{chem|Cu|2+}} + 2 e<sup>−</sup> → Cu || 0.339 ||2.0 || 119 || |
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|| [[Bismuth]] || 83 || 15 || 6 || {{chem|Bi|3+}} + 3 e<sup>−</sup> → Bi || 0.308 ||2.02 || 91 || |
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|| [[Technetium]] ☢ || 43 || 7 || 5 || {{chem|Tc|2+}} 3 e<sup>−</sup> → Tc || 0.3 ||1.9 || 53|| |
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|| [[Arsenic]] <sup><small>MD</small></sup> || 33 || 15 || 4 || {{chem|As|4|O|6}} + 12 {{chem|H|+}} + 12 e<sup>−</sup> → 4 As + 6 {{chem|H|2|O}} || 0.24 ||2.18 || 78 || |
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|| [[Antimony]] <sup><small>MD</small></sup> || 51 || 15 || 5 || {{chem|Sb|2|O|3}} + 6 {{chem|H|+}} + 6 e<sup>−</sup> → 2 Sb + 3 {{chem|H|2|O}} || 0.147 ||2.05 || 101 || |
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|| [[Bohrium]] ☢ || 107 || 7 || 7 || {{chem|Bh|5+}} + 5 e<sup>−</sup> → Bh || 0.1|| || ||† |
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|| [[Livermorium]] ☢ || 116 || 16 || 7 || {{chem|Lv|2+}} + 2 e<sup>−</sup> → Lv || 0.1||2.58|| ||† |
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|} |
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The simplified entries in the reaction column can be read in detail from the [[Pourbaix diagram]]s of the considered element in water. All elements not in this table are either not metals or have a negative standard potential. |
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Arsenic, antimony and tellurium are considered to be [[metalloid]]s rather than noble metals. |
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The black tarnish commonly seen on silver arises from its sensitivity to [[hydrogen sulfide]]: 2Ag + H<sub>2</sub>S + ½O<sub>2</sub> → Ag<sub>2</sub>S + H<sub>2</sub>O. Rayner-Canham<ref>{{cite book |last=Rayner-Canham|first=G|editor-last1=Scerri |editor-first1=E |editor-last2=Restrepo |editor-first2=G |title=Mendeleev to Oganesson: A multidisciplinary perspective on the periodic table |publisher=Oxford University |date=2018 |pages=195–205 |chapter=Organizing the transition metals|isbn=978-0-190-668532}}</ref> contends that, "silver is so much more chemically-reactive and has such a different chemistry, that it should not be considered as a 'noble metal'." In [[dentistry]], silver is not regarded as a noble metal due to its tendency to corrode in the oral environment.<ref> |
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{{cite book |last1=Powers |first1= JM|last2=Wataha|first2=JE|date= 2013|title= Dental materials: Properties and manipulation| url= |location=St Louis |publisher= Elsevier Health Sciences|page= 134|isbn= 9780323291507 |edition=10th}}</ref> |
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The relevance of the entry for water is addressed by Li et. al.<ref>{{cite book |last=Li |first=Y |last2=Lu|first2=D|last3=Wong|first3=CP|date=2010 |title=Electrical conductive adhesives with nanotechnologies |location=New York |publisher=Springer |page=179 |isbn=978-0-387-88782-1}}</ref> in the context of galvanic corrosion. Such a process will only occur when: |
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:"(1) two metals which have different electrochemical potentials are…connected, (2) an aqueous phases with electrolyte exists, and (3) one of the two metals has…potential lower than the potential of the reaction ({{chem|H|2|O}} + 4e +{{chem|O|2}} = 4 OH<sup><big>•</big></sup>) which is 0.4 V…The…metal with…a potential less than 0.4 V acts as an anode…loses electrons…and dissolves in the aqueous medium. The noble metal (with higher electrochemical potential) acts as a cathode and, under many conditions, the reaction on this electrode is generally {{chem|H|2|O}} − 4 e<sup><big>•</big></sup> − {{chem|O|2}} = 4 OH<sup><big>•</big></sup>)." |
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⚫ | The [[superheavy element]]s from [[hassium]] (element 108) to [[livermorium]] (116) inclusive are expected to be "partially very noble metals"; chemical investigations of hassium has established that it behaves like its lighter congener osmium, and preliminary investigations of [[nihonium]] and [[flerovium]] have suggested but not definitively established noble behavior.<ref>{{cite journal |last=Nagame |first=Yuichiro |last2=Kratz |first2=Jens Volker |last3=Matthias |first3=Schädel |date=December 2015 |title=Chemical studies of elements with Z ≥ 104 in liquid phase |journal=Nuclear Physics A |volume=944 |pages=614–639 |doi=10.1016/j.nuclphysa.2015.07.013|bibcode=2015NuPhA.944..614N |url=https://jopss.jaea.go.jp/search/servlet/search?5050598 }}</ref> [[Copernicium]]'s behaviour seems to partly resemble both its lighter congener mercury and the noble gas [[radon]].<ref name=CRNL>{{cite journal |last=Mewes |first=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 <!-- |volume= |issue= --> |date=2019 | |doi=10.1002/anie.201906966 |url=https://www.researchgate.net/publication/336389017|doi-access=free }}</ref> |
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Electronegativity is included since it is reckoned to be, "a major driver of metal nobleness and reactivity."<ref>{{cite journal |last1=Kepp |first1=K |date=2020 |title=Chemical causes of metal nobleness |journal=ChemPhysChem |volume= 21|issue= 5|pages=360-369 |doi=10.1002/cphc.202000013}}</ref> Predicted values for nihonium, flerovium, moscovium, and livermorium are given by Karol.<ref>{{cite journal |last1=Karol |first1=PJ |date=2020 |title=Extending electronegativities to superheavy Main Group atoms |journal=Chemistry International|volume= 42|issue= 3|pages=12-15 |doi=10.1515/ci-2020-0305}}</ref> |
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On account of their high electron affinity values,<ref>{{cite book |last=Viswanathan |first= B|author-link= |date=2002 |title= Catalysis: Principles and Applications|url= |location= Boca Raton|publisher=CRC Press |page= 291|isbn=}}</ref> the incorporation of a noble metal in the electrochemical [[photolysis]] process, such as platinum and gold, among others, can increase photoactivity.<ref>{{Cite journal|last1=Fujishima|first1=A.|last2=Honda|first2=K.|date=1972|title=Electrochemical Photolysis of Water at a Semiconductor Electrode|url=|journal=Nature|volume=238|issue=5358|pages=37–38|doi=10.1038/238037a0|pmid=12635268|bibcode=1972Natur.238...37F|s2cid=4251015}}; {{Cite journal|last=Nozik|first=A.J.|date=1977|title=Photochemical Diodes|url=|journal=Appl Phys Lett|volume=30|issue=11|pages=567–570|doi=10.1063/1.89262|bibcode=1977ApPhL..30..567N}}</ref> |
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==See also== |
==See also== |
Revision as of 09:02, 22 October 2020
In chemistry, the noble metals are metals that are resistant to corrosion and oxidation in moist air (unlike most base metals). In periodic table terms they correspond to the noble gases.[1] The short list of chemically noble metals (those elements upon which almost all chemists agree) comprises ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt), and gold (Au).[2]
More inclusive lists include one or more of mercury (Hg),[3][4][5] rhenium (Re),[6] and copper (Cu) as noble metals. On the other hand, titanium (Ti), niobium (Nb), and tantalum (Ta) are not included as noble metals although they are very resistant to corrosion.
While the noble metals tend to be valuable – due to both their rarity in the Earth's crust and their applications in areas like metallurgy, high technology, and ornamentation (jewelry, art, sacred objects, etc.) – the terms noble metal and precious metal are not synonymous.
The term noble metal can be traced back to at least the late 14th century[7] and has slightly different meanings in different fields of study and application. Only in atomic physics is there a strict definition, which includes only copper, silver, and gold, because they have completely filled d-subshells. For this reason, there are many quite different lists of "noble metals".
In addition to this term's function as a compound noun, there are circumstances where noble is used as an adjective for the noun metal. A galvanic series is a hierarchy of metals (or other electrically conductive materials, including composites and semimetals) that runs from noble to active, and allows one to predict how materials will interact in the environment used to generate the series. In this sense of the word, graphite is more noble than silver and the relative nobility of many materials is highly dependent upon context, as for aluminium and stainless steel in conditions of varying pH.[8]
Properties
Platinum, gold and mercury can be dissolved in aqua regia, a highly concentrated mixture of hydrochloric acid and nitric acid, but iridium cannot. The solubility of silver is limited by the formation of silver chloride precipitate.[9] Palladium and silver are, however, soluble in nitric acid. Ruthenium can be dissolved in aqua regia only when in the presence of oxygen, while rhodium must be in a fine pulverized form. Niobium and tantalum are resistant to all acids, including aqua regia.[1]
Physics
In physics, the definition of a noble metal is most strict. It requires that the d-bands of the electronic structure be filled. From this perspective, only copper, silver and gold are noble metals, as all d-like bands are filled and do not cross the Fermi level.[10] However, d-hybridized bands do cross the Fermi level to a small extent. In the case of platinum, two d bands cross the Fermi level, changing its chemical behaviour such that it can function as a catalyst. The difference in reactivity can easily be seen during the preparation of clean metal surfaces in an ultra-high vacuum: surfaces of "physically defined" noble metals (e.g., gold) are easy to clean and keep clean for a long time, while those of platinum or palladium, for example, are covered by carbon monoxide very quickly.[11]
Electrochemistry
The following table lists standard reduction potential in volts;[12][13]; electronegativity (revised Pauling); and electron affinity values (kJ/mol), for some metals and metalloids. Metals commonly recognised as noble metals are flagged with a ✣ symbol; elements marked ☢ are synthetic, radioactive, and short-lived; metalloids are denoted MD; values with a † are predicted; a blank na = not available or applicable.
Element | Atomic number |
Group | Period | Reaction | Poten- tial (V) |
Electro- negativity |
Electron affinity |
Note |
---|---|---|---|---|---|---|---|---|
Copernicium ☢ | 112 | 12 | 7 | Cn2+ + 2 e− → Cn |
2.1 | † | ||
Roentgenium ☢ | 111 | 11 | 7 | Rg3+ + 3 e− → Rg |
1.9 | † | ||
Darmstadtium ☢ | 110 | 10 | 7 | Ds2+ + 2 e− → Ds |
1.7 | † | ||
Gold ✣ | 79 | 11 | 6 | Au3+ + 3 e− → Au |
1.5 | 2.54 | 223 | |
Platinum ✣ | 78 | 10 | 6 | Pt2+ + 2 e− → Pt |
1.2 | 2.28 | 205 | |
Iridium ✣ | 77 | 9 | 6 | Ir3+ + 3 e− → Ir |
1.16 | 2.2 | 151 | |
Astatine ☢ | 85 | 17 | 6 | At+ + e− → At |
1.0 | 2.2 | 233 | |
Palladium ✣ | 46 | 10 | 5 | Pd2+ + 2 e− → Pd |
0.915 | 2.2 | 54 | |
Flerovium ☢ | 114 | 14 | 7 | Fl2+ + 2 e− → Fl |
0.9 | 2.21 | † | |
Osmium ✣ | 76 | 8 | 6 | OsO 2 + 4 H+ + 4 e− → Os + 2 H 2O |
0.85 | 2.2 | 104 | |
Mercury | 80 | 12 | 6 | Hg2+ + 2 e− → Hg |
0.85 | 2.0 | −50 | |
Rhodium ✣ | 45 | 9 | 5 | Rh3+ + 3 e− → Rh |
0.8 | 2.28 | 110 | |
Meitnerium ☢ | 109 | 9 | 7 | Mt3+ + 3 e− → Mt |
0.8 | † | ||
Silver ✣ | 47 | 11 | 5 | Ag+ + e− → Ag |
0.7993 | 1.93 | 126 | |
Ruthenium ✣ | 44 | 8 | 5 | Ru3+ + 3 e− → Ru |
0.6 | 2.2 | 101 | |
Polonium ☢ | 84 | 16 | 6 | Po2+ + 2 e− → Po |
0.6 | 2.0 | 136 | |
Nihonium ☢ | 113 | 13 | 7 | Nh+ + e− → Nh |
0.6 † | 2.09 | † | |
Tellurium MD | 52 | 16 | 5 | TeO 2 + 4 H+ + 4 e− → Te + 2 H 2O |
0.53 | 2.1 | 190 | |
Rhenium | 75 | 7 | 6 | Re3+ + 3 e− → Re |
0.5 | 1.9 | 6 | |
Water | 75 | 7 | 6 | H 2O + 4 e− +O 2 → 4 OH− |
0.4 | |||
Hassium ☢ | 108 | 8 | 7 | Hs4+ + 4 e− → Hs |
0.4 | † | ||
Copper | 29 | 11 | 4 | Cu2+ + 2 e− → Cu |
0.339 | 2.0 | 119 | |
Bismuth | 83 | 15 | 6 | Bi3+ + 3 e− → Bi |
0.308 | 2.02 | 91 | |
Technetium ☢ | 43 | 7 | 5 | Tc2+ 3 e− → Tc |
0.3 | 1.9 | 53 | |
Arsenic MD | 33 | 15 | 4 | As 4O 6 + 12 H+ + 12 e− → 4 As + 6 H 2O |
0.24 | 2.18 | 78 | |
Antimony MD | 51 | 15 | 5 | Sb 2O 3 + 6 H+ + 6 e− → 2 Sb + 3 H 2O |
0.147 | 2.05 | 101 | |
Bohrium ☢ | 107 | 7 | 7 | Bh5+ + 5 e− → Bh |
0.1 | † | ||
Livermorium ☢ | 116 | 16 | 7 | Lv2+ + 2 e− → Lv |
0.1 | 2.58 | † |
The simplified entries in the reaction column can be read in detail from the Pourbaix diagrams of the considered element in water. All elements not in this table are either not metals or have a negative standard potential.
Arsenic, antimony and tellurium are considered to be metalloids rather than noble metals.
The black tarnish commonly seen on silver arises from its sensitivity to hydrogen sulfide: 2Ag + H2S + ½O2 → Ag2S + H2O. Rayner-Canham[14] contends that, "silver is so much more chemically-reactive and has such a different chemistry, that it should not be considered as a 'noble metal'." In dentistry, silver is not regarded as a noble metal due to its tendency to corrode in the oral environment.[15]
The relevance of the entry for water is addressed by Li et. al.[16] in the context of galvanic corrosion. Such a process will only occur when:
- "(1) two metals which have different electrochemical potentials are…connected, (2) an aqueous phases with electrolyte exists, and (3) one of the two metals has…potential lower than the potential of the reaction (H
2O + 4e +O
2 = 4 OH•) which is 0.4 V…The…metal with…a potential less than 0.4 V acts as an anode…loses electrons…and dissolves in the aqueous medium. The noble metal (with higher electrochemical potential) acts as a cathode and, under many conditions, the reaction on this electrode is generally H
2O − 4 e• − O
2 = 4 OH•)."
The superheavy elements from hassium (element 108) to livermorium (116) inclusive are expected to be "partially very noble metals"; chemical investigations of hassium has established that it behaves like its lighter congener osmium, and preliminary investigations of nihonium and flerovium have suggested but not definitively established noble behavior.[17] Copernicium's behaviour seems to partly resemble both its lighter congener mercury and the noble gas radon.[18]
Electronegativity is included since it is reckoned to be, "a major driver of metal nobleness and reactivity."[19] Predicted values for nihonium, flerovium, moscovium, and livermorium are given by Karol.[20]
On account of their high electron affinity values,[21] the incorporation of a noble metal in the electrochemical photolysis process, such as platinum and gold, among others, can increase photoactivity.[22]
See also
References
- Brooks, Robert R., ed. (1992). Noble Metals and Biological Systems: Their Role in Medicine, Mineral Exploration, and the Environment. Boca Raton, Fla.: CRC Press. ISBN 9780849361647. OCLC 24379749.
- Notes
- ^ a b A. Holleman, N. Wiberg, "Inorganic Chemistry", Academic Press, 2001
- ^ A. Holleman, N. Wiberg, "Lehrbuch der Anorganischen Chemie", de Gruyter, 1985, 33. edition, p. 1486
- ^ "Edelmetall". www.uni-protokolle.de. Retrieved April 6, 2018.
- ^ "Dictionary of Mining, Mineral, and Related Terms", Compiled by the American Geological Institute, 2nd edition, 1997
- ^ Scoullos, M.J., Vonkeman, G.H., Thornton, I., Makuch, Z., "Mercury – Cadmium – Lead: Handbook for Sustainable Heavy Metals Policy and Regulation",Series: Environment & Policy, Vol. 31, Springer-Verlag, 2002
- ^ The New Encyclopædia Britannica, 15th edition, Vol. VII, 1976
- ^ "the definition of noble metal". Dictionary.com. Retrieved April 6, 2018.
- ^ Everett Collier, "The Boatowner’s Guide to Corrosion", International Marine Publishing, 2001, p. 21
- ^ W. Xing, M. Lee, Geosys. Eng. 20, 216, 2017
- ^ Hüger, E.; Osuch, K. (2005). "Making a noble metal of Pd". EPL. 71 (2): 276. Bibcode:2005EL.....71..276H. doi:10.1209/epl/i2005-10075-5.
- ^ S. Fuchs, T.Hahn, H.G. Lintz, "The oxidation of carbon monoxide by oxygen over platinum, palladium and rhodium catalysts from 10−10 to 1 bar", Chemical engineering and processing, 1994, V 33(5), pp. 363–369 [1]
- ^ G. Wulfsberg, "Inorganic Chemistry", University Science Books, 2000, pp. 247–249 ✦ Bratsch S. G., "Standard Electrode Potentials and Temperature Coefficients in Water at 298.15 K", Journal of Physical Chemical Reference Data, vol. 18, no. 1, 1989, pp. 1–21 ✦ B. Douglas, D. McDaniel, J. Alexander, "Concepts and Models of Inorganic Chemistry", John Wiley & Sons, 1994, p. E-3
- ^ Hoffman, Darleane C.; Lee, Diana M.; Pershina, Valeria (2006). "Transactinides and the future elements". In Morss; Edelstein, Norman M.; Fuger, Jean (eds.). The Chemistry of the Actinide and Transactinide Elements (3rd ed.). Dordrecht, The Netherlands: Springer Science+Business Media. ISBN 1-4020-3555-1.
- ^ Rayner-Canham, G (2018). "Organizing the transition metals". In Scerri, E; Restrepo, G (eds.). Mendeleev to Oganesson: A multidisciplinary perspective on the periodic table. Oxford University. pp. 195–205. ISBN 978-0-190-668532.
- ^ Powers, JM; Wataha, JE (2013). Dental materials: Properties and manipulation (10th ed.). St Louis: Elsevier Health Sciences. p. 134. ISBN 9780323291507.
- ^ Li, Y; Lu, D; Wong, CP (2010). Electrical conductive adhesives with nanotechnologies. New York: Springer. p. 179. ISBN 978-0-387-88782-1.
- ^ Nagame, Yuichiro; Kratz, Jens Volker; Matthias, Schädel (December 2015). "Chemical studies of elements with Z ≥ 104 in liquid phase". Nuclear Physics A. 944: 614–639. Bibcode:2015NuPhA.944..614N. doi:10.1016/j.nuclphysa.2015.07.013.
- ^ Mewes, J.-M.; Smits, O. R.; Kresse, G.; Schwerdtfeger, P. (2019). "Copernicium is a Relativistic Noble Liquid". Angewandte Chemie International Edition. doi:10.1002/anie.201906966.
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(help) - ^ Kepp, K (2020). "Chemical causes of metal nobleness". ChemPhysChem. 21 (5): 360–369. doi:10.1002/cphc.202000013.
- ^ Karol, PJ (2020). "Extending electronegativities to superheavy Main Group atoms". Chemistry International. 42 (3): 12–15. doi:10.1515/ci-2020-0305.
- ^ Viswanathan, B (2002). Catalysis: Principles and Applications. Boca Raton: CRC Press. p. 291.
- ^ Fujishima, A.; Honda, K. (1972). "Electrochemical Photolysis of Water at a Semiconductor Electrode". Nature. 238 (5358): 37–38. Bibcode:1972Natur.238...37F. doi:10.1038/238037a0. PMID 12635268. S2CID 4251015.; Nozik, A.J. (1977). "Photochemical Diodes". Appl Phys Lett. 30 (11): 567–570. Bibcode:1977ApPhL..30..567N. doi:10.1063/1.89262.
External links
- noble metal – chemistry Encyclopædia Britannica, online edition
- To see which bands cross the Fermi level, the Fermi surfaces of almost all the metals can be found at the Fermi Surface Database
- The following article might also clarify the correlation between band structure and the term noble metal: Hüger, E.; Osuch, K. (2005). "Making a noble metal of Pd". EPL. 71 (2): 276. Bibcode:2005EL.....71..276H. doi:10.1209/epl/i2005-10075-5.