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Lone pairs location

Posted: Sat Dec 07, 2019 9:12 pm
by Baoying Li 1B
How do you where the lone pairs lie in a trigonal pyramidal shape and in a seesaw shape?

Re: Lone pairs location

Posted: Sat Dec 07, 2019 9:24 pm
by zoedfinch1K
Trigonal pyramidal is derived from the tetrahedral shape. Remember that in a tetrahedron, the bond angles are all set at an equal distance apart: 109.5 degrees. Thus, no matter where you place the lone pairs, the shape will always look the same.

The see-saw shape is derived from a trigonal bipyramidal shape. When placing lone pairs, you would place them on the EQUATORIAL PLANE. This is the opposite for octahedral electronic structures as you would place lone pairs on the axial plane (this is how you get shape like square planar).

Re: Lone pairs location

Posted: Sat Dec 07, 2019 9:29 pm
by Connor Ho 1B
Just remember that in any geometry, lone pairs are placed as far as possible from other atoms and try to interact with other atoms as little as possible. Put the lone pair wherever it is next to the least amount of atoms.

Re: Lone pairs location

Posted: Sat Dec 07, 2019 9:30 pm
by Vicki Liu 2L
To add on to the previous answer, the reason the lone pair should be placed on the equatorial plane is because this is what minimizes the repulsion between the lone pair and other outer atoms, which makes the molecule most stable.