Polarity of Water: Exploring Electrical Neutrality

[Tam Le]

I understand that, in the molecule H₂O, O has a slight negative charge while the two H's have a slight positive charge. However, I do not understand why the molecule as a whole is considered electrically neutral.

Also, how is electrically neutral defined? Does it mean that the electrical forces of attraction and repulsion negate each other?

For example, in this drawing, the attraction between the O and the positively charged object would equal the repulsion between the H's and the positively charged object. Is this what being electrically neutral means?

 

[dark knight13]

the oxygen atom is written as [O][/2-] while Hydrogen ion is [H[/+] so the net charge on the molecule will be zero, hence nuetral.

 

[Borek]

Electrically neutral means - total charge is zero.

Actually that's the starting point here, not the other way around. We know water molecule is electrically neutral, so we know even if the charge distribution is not uniform, whatever excess of positive charge is present in some place (or some places) of the molecule, identical amount of negative charge is present in other places. In the case of water molecule it means that the negative charge on the oxygen atom is twice as large as the positive charge on each hydrogen atom.

Even if a molecule is electrically neutral it can have non-uniform charge distribution, and it can attract other electrically neutral molecules. We call it - in the simplest form - dipole-dipole interaction.