[Enceph]

Okay, well when an atom of Magnesium comes in contact with an atom of Oxygen (O2), does it form Magnesium Oxide, or Magnesium Dioxide?

My text book says Magnesium Oxide, but I don't see how this makes sense.  Wouldn't it be MgO2 (magnesium dioxide) ?

Is O2 two atoms of oxygen that we breathe?  Because I always see Oxygen as O2, but one Oxygen atom by itself is simply O, right?

Thanks

[lemonoman]

O₂ is definitely the oxygen that you breathe.

When magnesium metal oxidizes, TWO atoms of magnesium react with ONE molecule of oxygen:

2 Mg + O₂ --> 2 MgO

And magnesium oxide is what is formed

The reaction Mg + O₂ --> MgO₂ does not happen....it is impossible.

[Borek]

The reaction Mg + O₂ --> MgO₂ does not happen....it is impossible.

Never say never. Have you ever heard about peroxides? Superoxides?

[lemonoman]

I'm well aware of them.  I just wasn't going to bring them up.

I guess 'impossible' wasn't the right word, but I think I got my point across.

[Enceph]

Why is 2 Mg in the equation?

Shouldn't it be (Mg)2? 

But how does it oxidize if my text book's example is one atom of Magnesium, and two atoms of Oxygen?  It doesn't have two atoms of Magnesium.

Thanks

[agrobert]

Lemonman's equation is balanced.  Your book may not be.  It takes 2 Mg atoms to reduce O₂.  2 atoms of Mg⁰ are oxidized to two atoms of Mg⁺² making two molecules of MgO.  And oxygen (O₂) is reduced to 2 atoms of O^-2.  This way the charges and the equation are balanced.

[Enceph]

So then my book is incorrect in saying that Mg + O2, make Magnesium Oxide (MgO) ?

[Borek]

So then my book is incorrect in saying that Mg + O2, make Magnesium Oxide (MgO) ?

It is OK. Every reaction equation can be written as 'skeletal' - like

Mg + O₂ -> MgO

or balanced:

2Mg + O₂ -> 2MgO

they both refer to the same process of magnesium oxidation, they both show correct reagents and products. The difference is that skeletal equation can't be used for stoichiometric calculations, while balanced one - can be.

Why is 2 Mg in the equation?

Shouldn't it be (Mg)2?

No. Free oxygen - as several other gases - usually forms diatomic molecules (that's the form present in the air). That's why it is used in the form of O₂ in reactions. Metallic Mg doesn't form such molecules, so it is just Mg.

[Enceph]

So the rules that I'm working with have exceptions, it just sucks that when these things come up in my books, they leave me wondering if its an error, or correct, but it turns out being an 'exception' to the rule, though they don't explain it.

Okay, so will Mg always come out as,  2 Mg, 3 Mg, 4 Mg, etc?

Or can Mg form a molecule of Mg3?  (Knowing now that it can't form a molecule of Mg2)