2 Lone pairs means more polarity?

[September24]

Why is it that having 2 lone pairs makes a molecule polar but having 1 or 3 does not. It would seem to me that 3 lone pairs would pull electrons more and segregate the charge creating partial charges. 2 bonds and 2 lone pairs looks like a partially symmetrical molecule to me.

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[monkeyvokes]

??

in the case of water, the 2 lone pairs result in a bent shape. The dipoles do not cancel out and you have a net polarity. Polarity occurs on a continuum, some molecules more polar than others. Nitrogen often has a single loan pair and often has somewhat polar bonds, but not quite as polar as oxygen.
When oxygen has 3 lone pairs it has more than a partial charge, it has a full negative charge.

 

[eudovcic]

H2O has 2 lone pairs and 2 bonds and is polar, H3O+ has 1 lone pair and 3 bonds and is polar.