Which metals react with CO
|N / A||Mg||Al||Si||P.||S.||Cl||Ar|
Precious metals are metals that do not react with water or aqueous acid solutions to form hydrogen, i.e. have a more positive normal potential than hydrogen. For this reason, they often appear dignified in nature.
The precious metals include:
Copper, silver, gold, ruthenium, rhodium, palladium, rhenium, osmium, iridium, platinum, mercury.
In the chemical sense, precious metals are all metals that have a positive standard potential in relation to hydrogen in the electrochemical series. Traditionally, however, copper is not counted as a precious metal, although it actually belongs to it in the chemical sense. Hence it is sometimes referred to as a semi-precious metal. The artificial elements Bohrium, Hassium, Meitnerium, Darmstadtium, Roentgenium and Element 112 are also believed to be precious metals.
In addition to the precious metals, there are also some metals which, as a result of their passivation, sometimes have a corrosion resistance that in some cases even exceeds that of some precious metals. These are the elements of the 4th subgroup (titanium, zirconium and hafnium), those of the 5th subgroup (vanadium, niobium and tantalum) and those of the 6th subgroup (chromium, molybdenum and tungsten). Other technically important metals that form passive layers are zinc (12th subgroup), aluminum (3rd main group) as well as silicon and lead (4th main group). In addition, noble metals are often not at all "noble" in relation to very electropositive metals, but here often readily and with the release of energy they form intermetallic phases.
In the physical sense, the amount of precious metals is significantly smaller; it's just copper, silver and gold. The criterion for classification is the electronic band structure. The three metals listed all have completely filled d-bands, which therefore do not contribute to conductivity and practically no reactivity. This applies to platinum, for example. B. not. Two D-type bands cross the Fermi level. This leads to a different chemical behavior, which is why platinum, unlike gold, is also often used as a catalyst. The difference in the production of pure metal surfaces in an ultra-high vacuum is particularly noticeable. While z. B. Gold is comparatively easy to prepare and remains pure for a long time after preparation, carbon monoxide binds to platinum or palladium very quickly.
In the parlance of sports reports, especially during the Olympic Games, bronze is also mistakenly counted as a precious metal.
Redox series | Base metals | Precious metal divorce
Which bands cross the Fermi level can be seen on the page The Fermi Surface Database.
- German Precious Metals Society
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