How is this linear?

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Natalie Noble 1G
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How is this linear?

Postby Natalie Noble 1G » Fri Jun 01, 2018 3:04 pm

When doing a practice problem for naming shape I ran into some trouble. The molecule had 5 bonding sites which I know is trigonal bipyramidal. However, three of the boding sites were lone pairs, and I know the repulsion from the lone pair changes the shape. So I thought the three lone pairs didn’t cancel out their repulsions, so I thought the molecule would be bent, but it is actual linear. Could someone explain this for me.

Fiona Grant 1I
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Joined: Fri Apr 06, 2018 11:03 am

Re: How is this linear?

Postby Fiona Grant 1I » Fri Jun 01, 2018 3:04 pm

You have to imagine it in a three-dimensional perspective, rather than how it looks in a Lewis structure. In a trigonal bipyramidal 3D shape, there are 3 atoms in a trigonal planar arrangement, 1 atom on top, and the other atom below. In this molecule, which has 3 lone pairs, these lone pairs are in the trigonal planar arrangement. Therefore, factoring in the lone pair repulsion, they all exert equal repulsion force on each other, so the 2 atoms will be in a linear arrangement.

Maria Roman 1A
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Joined: Fri Apr 06, 2018 11:04 am

Re: How is this linear?

Postby Maria Roman 1A » Sun Jun 03, 2018 12:24 am

This attachment helps visualize the molecule's linear shape

3508.gif (3.17 KiB) Viewed 164 times

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