Position of Lone Pairs in H20

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Jasmine Reddy DIS 1E
Posts: 34
Joined: Fri Sep 28, 2018 12:17 am

Position of Lone Pairs in H20

Postby Jasmine Reddy DIS 1E » Sun Nov 18, 2018 10:57 pm

If lone pair-lone pair repulsion is the strongest, and lone pairs want to maximize the distance between themselves, then why in H20 are the two lone pairs next to each other on the oxygen (resulting in a bent shape), as opposed to one pair being on top of the oxygen, and one pair being below the oxygen (which, I'm guessing, would result in a more linear shape)? Is it because the oxygen is more electronegative than the hydrogens?

405169322
Posts: 22
Joined: Fri Sep 28, 2018 12:25 am

Re: Position of Lone Pairs in H20

Postby 405169322 » Sun Nov 18, 2018 11:10 pm

I believe the two lone pairs on the top of the oxygen, creating the bent shape, is because of the overall polarity of the molecule. The two hydrogen atoms both have a partial positive helps maintain the polarity and therefore would repulse the two lone pairs. Not certain but I hope that helps.

Tessa Lawler 1A
Posts: 57
Joined: Fri Sep 28, 2018 12:18 am

Re: Position of Lone Pairs in H20

Postby Tessa Lawler 1A » Sun Nov 18, 2018 11:43 pm

That’s a good question. It would probably be because of the polarity of the molecule as a whole and its desire to stay that way.

Nell Mitchell 1E
Posts: 31
Joined: Fri Sep 28, 2018 12:16 am

Re: Position of Lone Pairs in H20

Postby Nell Mitchell 1E » Sun Nov 18, 2018 11:50 pm

It's because shape is determined by number of regions of electron density and h2o has 4 electrons density regions (2 bonded, 2 lone pairs). When there's 4 regions of density the shape is trigonal pyramidal. But then because only two are bonded the other two do not contribute to the overall shape but the density of the lone pairs keeps the O2 in the bent shape. No matter which two you make bonded and which two you make lone pairs, the shape will always be bent.


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