Lone pair electrons affecting shape

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Shirley Liu 2I
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Joined: Fri Sep 28, 2018 12:16 am

Lone pair electrons affecting shape

Postby Shirley Liu 2I » Sun Nov 25, 2018 10:34 pm

How do we know if lone pairs should occupy an equatorial or axial position to maximize their bond angles? For example, how do we know to "take off an atom" off the equatorial axis on a trigonal bipyramidal molecule to get a see saw shape instead of "taking off the atom" from the axial position? And will this "atom" always come off the equatorial axis to get see saw when there is a lone pair?

Andrew Bennecke
Posts: 62
Joined: Fri Sep 28, 2018 12:15 am

Re: Lone pair electrons affecting shape

Postby Andrew Bennecke » Sun Nov 25, 2018 11:19 pm

We always remove the termianl atom from the equatorial plane because this maximizes the bond angles. The two atoms on the axial plane will become just slightly less than 90 apart from those on the equatorial plane, but if we were to remove a terminal atom from the axial plane, the 3 remaining atoms on the equatorial plane would all push towards the remaining axial atom, not occupying the optimal bond angles.

Jeremy Feng 1A
Posts: 30
Joined: Fri Sep 28, 2018 12:18 am

Re: Lone pair electrons affecting shape

Postby Jeremy Feng 1A » Mon Nov 26, 2018 10:34 am

Building off of the previous reply, bond angles need to be maximized because of electron repulsion. Since electrons have the same charge, they tend to repel away from each other, creating the largest bond angle possible.


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