Why do lone pair electrons repel each other more strongly ?

[annatar]

In VSEPR theory, lone pairs repel each other more strongly than bonding pairs do, therefore they bend the molecule and determine its geometry.

But why does that happen? What makes the repulsion stronger?

Thanks for your help

 

[DanP]

In VSEPR theory, lone pairs repel each other more strongly than bonding pairs do, therefore they bend the molecule and determine its geometry.

But why does that happen? What makes the repulsion stronger?

Thanks for your help

Because a bonding electron pair is involved in a sigma bond with another atom. Hence is at a greater distance from the nucleus of the central atom than a non bonding pair. I think you can find explained in those lectures all basic concepts of chemistry

http://ocw.mit.edu/OcwWeb/Chemistry/5-112Fall-2005/VideoLectures/index.htm

 

[DrDu]

There are two points of importance, here:
1. The repulsion between electrons on different atoms is much smaller than between electrons on the same atom.
2. In a truly covalent bond, there is only one electron of the two per bond (at least on the mean) at a given atom as compared to two in a lone pair.

This is most clear in the limit, where the atoms are very far apart.