# Why are metal oxides basic and non-metals' acidic or neutral

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.

• >but is not satisfactory. || what the answer you linked lacks? – permeakra Nov 14 '14 at 9:21
• So how is this story goes with water? – Greg Apr 22 '15 at 11:48
• – Mithoron Apr 22 '15 at 12:05

## 2 Answers

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: $$\ce{CO2 + H2O -> H2CO3}$$ $$\ce{SO3 + H2O -> H2SO4}$$

• 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. – bon Sep 6 '15 at 13:22
• 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. – bon Sep 6 '15 at 17:27
• so they are acidic because they form acids? Sorry I dont know much about Arrehinius definition...only know the Brownsted Lowry one – MartianCactus 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:

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

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

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

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