Thread: Iron

OK, so Magnesium reacts with oxygen on the corrosion level and on the combustion level. It oxidizes slowly but it also burns. Iron, on the other hand, corrodes, oxides slowly, but when it is heated to high temperatures it doesn't burn. So what keeps Iron from burning like Magnesium? They're both metals, but is it because Magnesium has a very reactive ion (+2) or what?

I would guess that it has something to do with Magnesium not being a transition metal. Do any of the transition metals burn?

i think the reason is rather that magnesium is an alkaline metal.
afaik, all alkaline and alkali metals reacts strongly to oxygen.

Iron does burn but like most metals (including magnesium) it just requires a high surface area. If you ignite a piece of iron wool and place it in pure oxygen it burns quite violently to give iron(III) oxide or Hematite (see.. http://www.youtube.com/watch?v=q6eIqNpdvlw ) Even on its own you can quite easily burn iron wool with a hot enough flame i.e. bunsen burner. The rest of the tranisiton metals vary but there are certainly examples of metals that will combust. A common example is copper which burns with a green flame as it forms the oxide.

Yep you can burn steel wool with a cigarette lighter, then if you look at the 'ends' you will see it has actually melted into small balls. THis does not work with strands of copper wire of the same diameter, which has a lower melting point than steel.....

I was told this effect is a spinoff of thr 'seebeck' effect as the ends of the strands are heated (in the Iron) electrons move to the cooler region, oxygen molecules are then attracted to the hot end where they aid combustion, in copper of course the electrons flow towards the hot end and therefore do not attract the oxygen molecules. I have never seen this written, it was explained, can anybody shed light on it?

i think we discussed this in my chemistry class in highschool way back, doesnt it have something to do with the carbon levels?

It has to do with Zeff and electron configuration. Mg only has 2 valence shell electrons and a weak pull on them so it's reactivity would be greater than that of Fe, in generally, with any fairly electronegative species that wants to take them away.

Yes, that's what I thought. I never knew you could burn steel wool. Gotta try that someday and see what I get...

Originally Posted by The P-manator

Yes, that's what I thought. I never knew you could burn steel wool. Gotta try that someday and see what I get...

You get... Burnt steel wool - dont forget to look at the ends with a magnifying glass!