How can H3O (hydronium) exist?

Question

I'm learning chemistry at school, and we've been told this: oxygen has 2 negative charges, and hydrogen has a single positive charge. This means that two hydrogens can bond with one oxygen, forming water.

So how does hydronium exist? Is it truly H3O, or is it H2O with a hydrogen stuck on by dispersion forces or something?

Thanks!

Answer 1

Heavy water,dirty water.

Answer 2

Hydronium is the hydronium ion H3O+.  H3O does not exist for the reasons you point out.  Hydronium ion also has other forms.  Actually in water you also find H5O2+ and H7O3+

Answer 3

http://en.wikipedia.org/wiki/Hydronium