Reactivity series of metals

[jyoticlub]

Though reactivity series has been taught to us from grade 6 , I found a problem not in learning but something else.

 

The last metal was gold but I want to know why can't platinum be there at the bottom.Is it someyhing to do with its radioactivity , please reply me back

 

Thanks

[H2SO4]

the most common isotope of platinum is not radioactive. I didnt know there was a radioactive isotope for platinum. It should be there at the bottom.

 

Maybe it has something to do with its catalitic (being a catalyst in several reactions) properties. This is the only thing i can think of. Anyway, i thought iridium was the most noble metal known.

[collector]

...iridium was the most noble metal known.

 

The term nobility is not uniqely defined from a chemical point of view. Ir is not attacked by aqua regia in any concentration, not even finely divided metal. Au is readily attacked by and dissolved in aqua regia (fast), Pt is dissolved but much slower. But, Au is not oxidized in air at any temp, Ir is attacked even below 1000 deg C, IrO2 is formed. So, which one of these 2 metal is "the most noble"? It is a question of reactivity, and then the reactivity must be specified/defined towards/relative some other species.

 

The electrochemical series is for species (not only metal ions) in water solution. The reason that the redox couple Li+/Li has a lower voltage than Na+/Na, which in turn is lower than K+/K, is solvatization. In water solution that will be hydratization. The result is that by the relative voltages of alkali metal ions i water solution, it looks like Li is the least noble alkali metal, and Cs is the most noble of them. We know from the reactivity of alkali metals towards oxygen and water that it is the opposite situation, at least for the metals exposed to air or moisture.

 

And, the reactivity of alkali metals is not uniqely defined. The reactivity of alkali metals towards halogens, chacogens, acids (and water) increases with increasing atomic number. But, the reactivity of alkali metals towards hydrogen, nitrogen, carbon decreases with increasing atomic number. So Li is the most reactive alkali metal toward nitrogen, not Cs. Li reacts with atmospheric nitrogen at roome temperature and a atmospheric pressure.

[budullewraagh]

just a correction: the most noble alkali metal is sodium.

[jdurg]

Potassium has to be the most obnoxious of the alkali metals. Looking at my chunk of potassium, I see a couple of very tiny spots on there which have an orange/brown color to them. I really wish these superoxides wouldn't form. Now I have to CAREFULLY remove those small pieces of the metal and try to find a more oxygen free containment for my potassium.

[collector]

just a correction: the most noble alkali metal is sodium.

 

In what respectis is it "most noble"? Relative what? Sodium is more noble (i.e. less reactive) than lithium with respect to hydrogen, nitrogen, carbon. But sodium is less noble (i.e. more reactive) than lithium with respect to halogens, chalcogens, acids.

 

We see that when reacting sodium and lithium respectively with water. Sodium reacts much more violently, even with ignition, if finely divided or larger chunks. Lithium does not ignite, although the reaction is vigorous.

[MulderMan]

when talking of elements, what is the definition of noble? i understand about the noble gasses, but ive never heard the word used otherwise.