# Need help ly, due tomorrow

1. Sep 29, 2004

### needhelpperson

Need help urgently, due tomorrow...

When metal oxides react with water, the oxygen generally ends up as the hydroxide ion, separate from the metal. In contrast, when nonmetallic oxides react with water, the oxygen ends up as part of the nonmetals species. What connection is there between this contrasting behaviour of metal and nonmetal oxides and ionization energies?

I know that metal oxides are polar and nonmetal oxides are nonpolar, and i can explain it using those definitions. But I have no idea how to explain this using ionization energy. This is due tomorrow. Please help

2. Sep 30, 2004

### chem_tr

I think it is too late now, but if there is similar homeworks in the future, you can use this analogy.

The primary ionization energies (1IE) of metal ions are very low, whereas it is very high in ametals, as you know. When a metal oxide (say, sodium oxide) is reacted with water, the following reaction is likely to occur:

$$Na_2O + H_2O \rightarrow 2~Na^+ + OH^-$$

An ametal oxide (for example, As2O3) gives arsenite acid:
$$As_2O_3 + H_2O \rightarrow 2~HAsO_2$$

Here, as sodium has a low 1IE, it can easily form a cation to allow the remaining as an anion. Therefore, Na+ needs OH-.

But arsenic(III) oxide forms an anion due to inefficient 1IE, so a complex [AsO2]- will be formed, with accompanying H+.

Regards