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xskater
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Can anyone explain why a water molecule's TWO lone pair are not at opposites ends of the oxygen atom ?

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sazzles
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(Original post by xskater)
Can anyone explain why a water molecule's TWO lone pair are not at opposites ends of the oxygen atom ?

Thanks...
In a water molecule, there are four negative centres (two lone pairs and two bonding pairs of electrons). To ensure maximum repulsion between all these negative centres, they are each approximately 109 degrees apart (like in a molecule of methane). If the lone pairs were at opposite ends, they would be closer to the bonding pairs of electrons and therefore would repel until they were further apart.

(By the way, the bond angle in water isn't 109 degrees, its nearer 104.5 degrees because lone pair repulsion is greater than the bonding pair repulsion, due to charge density)

Hope this is useful.
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