Extracting metals from their compounds?

[Gareth56]

Can someone explain why if a metal is readily oxidized why the resulting ions or compounds are difficult to reduce? I understand why something like sodium wants to loose its lone 3s electron to form say NaCl but then can't associate this fact with the difficulty in obtaining Na metal. Is it because Na prefers to exist in nature as as ionic compound rather than exist as metallic Na?

 

Thanks

[Fuzzwood]

You might want to look up the octet rule.

[Gareth56]

I thought I taken that into account above by saying that Na likes to combine with say Cl to form NaCl making NaCl (each atom has a full shell of electrons). However that does't explain why Na prefers to do this rather than exist as Na. That is because it's so easily oxidised why is Na so difficult to reduce. The OIL part is easy by the RIG is difficult!!

 

I suppose it's a deeper question.

[John Cuthber]

A way to look at it is that the electrons have to be somewhere.

So, for example, if you have some chlorine gas and some sodium metal, there's a pair of electrons in each chlorine molecule that are shared between the two atoms (making Cl₂) because each Cl atom is short of an electron. Also there's some sodium that's able to better accommodate those electrons.

 

The electrons would be in a lower energy state if they were stuck to the chlorines.

So they transfer across to give sodium ions and chlorine ions.

Even better, those ions can now pack themselves into a nice orderly crystal so the + charges are surrounded by - charges (which is nice, because they are attracted to one another) and the negatively charged Cl^- ions are surrounded by the Na⁺ ions (and again, they attract each other so they are happy with the arrangement).

The electrons are something like 2000 to 400,000 times lighter than the ions so it's the electrons that can move easily.

They move to the places where they are most stable.

 

The detailed answer to why the electrons are easy to remove from sodium is more complex but this might help.

http://en.wikipedia.org/wiki/Shielding_effect

[Gareth56]

So it's all about the electrons wanting to be in a lower energy state and it's easier in energetic terms for Na to give Cl its lone electron than for Na to be given and electron (as in a reduction reaction).

 

Thank you John.

[magnocrat]

You are right Gareth sodium is far to reative to exist as a metal. Yet it is strange that oxygen fills our atmosphere inspite of its active nature. Gold is the only metal to occur naturally and has been the result of many deaths in gold rushes.

[hypervalent_iodine]

You are right Gareth sodium is far to reative to exist as a metal. Yet it is strange that oxygen fills our atmosphere inspite of its active nature. Gold is the only metal to occur naturally and has been the result of many deaths in gold rushes.

That's plain untrue. A number of metals besides gold may be found naturally in their elemental state, either as an alloy or singly.

[John Cuthber]

It is less strange that the air contains oxygen, when you consider where it comes from.

If there were no plants using sunlight to cleave it from water, there wouldn't be any oxygen.

[magnocrat]

Hypervalent I stand corrected you are quite right I checked and was surprised. I picked the fact up at school many years ago whdn talking about chemical activity. It goes to show one should even check what seems obvious.