molecular shape vs molecular geometry

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

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Maggie Doan 1I
Posts: 61
Joined: Fri Sep 28, 2018 12:24 am

molecular shape vs molecular geometry

Postby Maggie Doan 1I » Sat Nov 24, 2018 7:51 pm

What is the difference between molecular shape and geometry? Which one depends on lone pairs?

Hanniel U 2B
Posts: 76
Joined: Fri Sep 28, 2018 12:16 am

Re: molecular shape vs molecular geometry

Postby Hanniel U 2B » Sat Nov 24, 2018 8:03 pm

Molecular geometry usually includes the lone pair on the central atom. I call this the parent shape. While Molecular shape just describes the shape excluding the lone pair on the central atom. Make sure to differentiate both if or when asked to name shape. An example I like to use is SO2. The molecular geometry or parent shape for SO2 is Trigonal Planar because of the lone pair on S but the molecular shape is bent or angular.

Ariel Cheng 2I
Posts: 67
Joined: Fri Sep 28, 2018 12:29 am

Re: molecular shape vs molecular geometry

Postby Ariel Cheng 2I » Sat Nov 24, 2018 8:35 pm

Looking at VSEPR notations might help. For AX4, a molecule without lone pairs, both its molecular and electron geometry are tetrahedral. For AX3E, its molecular geometry would be trigonal pyramidal but its electron geometry is tetrahedral.

Chloe Thorpe 1J
Posts: 77
Joined: Fri Sep 28, 2018 12:16 am

Re: molecular shape vs molecular geometry

Postby Chloe Thorpe 1J » Sat Nov 24, 2018 10:06 pm

What the other people said is right, I think. Usually, Prof. Lavelle says the molecular geometry first (the one including lone pairs), then determines molecular shape (the one only including bound atoms).


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