## Sampling 4

(Polar molecules, Non-polar molecules, etc.)

jessicasilverstein1F
Posts: 87
Joined: Wed Sep 30, 2020 9:57 pm

### Sampling 4

How many outer atoms and lone pairs are present in a molecule with a square pyramidal shape?

How are we supposed to determine this?

IsaacLaw1E
Posts: 63
Joined: Wed Sep 30, 2020 9:58 pm
Been upvoted: 1 time

### Re: Sampling 4

You should think about how a square pyramidal shape could be formed from any of the basic shapes by removing bonding pairs and replacing them with lone pairs. For instance, you can form a square pyramidal shape by taking an tetrahedral shape and removing any one of the bonding pairs and replacing it with a lone pair. Then, the remaining bonding pairs kinda looks like a square with one pair going straight up like a pyramid. From there, you can find how many bonding and lone pairs are in that shape (you had six bonding pairs and you made one a lone pair).

Stephen Min 1I
Posts: 60
Joined: Wed Sep 30, 2020 10:01 pm

### Re: Sampling 4

A square pyramidal shape has 5 outer atoms and one lone pair. In addition to the above comment, you can also determine this by memorizing the formula for each shape. In this case, a square pyramidal is AX5E. X = outer atoms, E = lone pair.

Isabelle Hales 3L
Posts: 63
Joined: Wed Sep 30, 2020 9:41 pm
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### Re: Sampling 4

To add on, I find it best to work backwards when determining the 3D molecule that involves lone pairs. With the square pyramidal shape, we know that one region was removed from an octahedral shape. Thus, we had a total of 6 regions of electron density but removed 1 to create the square pyramidal shape. Using that reasoning, we can determine that we have 1 lone pair and 5 outer atoms. This logic can apply to other problems as we can examine which regions of electron density were "lost" to lone pairs in order to create the current shape from an old shape, and then use the old shape to determine how many outer atoms we have.

Tobie Jessup 2E
Posts: 59
Joined: Wed Sep 30, 2020 10:02 pm

### Re: Sampling 4

IsaacLaw1L wrote:You should think about how a square pyramidal shape could be formed from any of the basic shapes by removing bonding pairs and replacing them with lone pairs. For instance, you can form a square pyramidal shape by taking an tetrahedral shape and removing any one of the bonding pairs and replacing it with a lone pair. Then, the remaining bonding pairs kinda looks like a square with one pair going straight up like a pyramid. From there, you can find how many bonding and lone pairs are in that shape (you had six bonding pairs and you made one a lone pair).

this was very helpful thank you!