Recently I came across the fact: Metal oxides basic and non-metals' acidic or neutral.

Searching for it, partly my query is solved, as I found:

Metal oxides or $\ce{O2-}$ forms $\ce{OH-}$ after hydrolysis in the following reaction so metal oxides are basic in aqeous solutions. $$\ce{O2- + 2H2O->4OH-}$$

I think this might happen as metal form ionic compunds and non-metals form covalent and some of them may not even react tus neutral.

I've got only a little $5\%$ of the exact reason, therefore I wish if someone could explain the whole process/fact. I considered Arhenius concept.

Note My question is partly answered here, but is not satisfactory.


We have learnt that metallic oxides are basic nature. This is because the oxides of metals like $\ce{MgO}$ or $\ce{CaO}$ or $\ce{Na2O}$ form hydroxides in their aqueous solutions. For example: $$\ce{K2O + H2O -> 2KOH}$$ $$\ce{MgO + H2O -> Mg(OH)2}$$

But when non-metallic oxides dissociate into their constituent ions in water, they give $\ce{H+}$ ions in their aqueous solutions forming acids For example: $$\ce{CO2 + H2O -> H2CO3}$$ $$\ce{SO3 + H2O -> H2SO4}$$

  • 3
    $\begingroup$ This just restates information in a previous answer and the equations are also unbalanced. Perhaps you could clean this up a little and add some more detail. $\endgroup$
    – bon
    Sep 6 '15 at 13:22
  • $\begingroup$ I have improved the formatting of your post using $\LaTeX$. For more information on how to do this yourself please see here and here. Additionally, you can visit this chatroom for more assistance. $\endgroup$
    – bon
    Sep 6 '15 at 17:27
  • $\begingroup$ so they are acidic because they form acids? Sorry I dont know much about Arrehinius definition...only know the Brownsted Lowry one $\endgroup$ Sep 14 '16 at 16:42

Metal oxides like $\ce{CaO}$ and $\ce{Na2O}$ react with water and give hydroxides:

$\ce{CaO + H2O <=> Ca(OH)2}$

$\ce{Na2O + H2O <=> 2 NaOH}$

While non-metal oxides like $\ce{CO2}$ and $\ce{SO2}$ react with water and give acids:

$\ce{CO2 + H2O <=> H2CO3 <=> H+ + HCO3-}$

$\ce{SO2 + H2O <=> H2SO3 <=> H+ + HSO3-}$

  • 2
    $\begingroup$ can you use technical terms, thermodynamics, kinetics, bonding theories or other theoretical explanations? $\endgroup$
    – RE60K
    Nov 14 '14 at 16:02
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    $\begingroup$ It still didn't explain why. $\endgroup$ Nov 16 '14 at 13:52

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