Seesaw Shape

[Madeleine Farrington 1B]

In class Dr. Lavelle discussed and modeled the seesaw shape, explaining that it had a single lone pair of electrons and then four sets of bonded electrons with other molecules. He teetered the model back and forth, explaining that this was where the shape got its name, but I am confused about why this shape would not have a stable four leg base if the lone pair of electrons was repelling the other four sets of bonded electrons equally?

[Chris Fults 1C]

I am a bit confused about this question. I have always assumed that the lone electron pair was above the central atom and that one element was on the right, one element was on the left, and two elements were on the bottom of the central atom. What I pictured below. This would give it the seesaw shape. Did professor Lavelle say this was incorrect?

..
|
X---C---X
/ \
X X

[Chris Fults 1C]

The image did not come out right the lone electrons were above the C as well as the two Xs.

[JulietOttenberg-1C]

I think this is because the lone pair repels the bonds that are closer to it more than the other bonds. Also, the bonds themselves repel eachother, so this shape is what occurs when all this repulsion balances out.

[Cameron Smith 1I]

There are 5 regions of electrom density creating a trigonal bipyramidal e- arrangement. Since one region of e- density is a lone pair the result after the spacing out of the atoms and condensing of angles is a seesaw.