T-shape vs. trigonal

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lizzygaines1D
Posts: 52
Joined: Thu Jul 13, 2017 3:00 am

T-shape vs. trigonal

Postby lizzygaines1D » Sun Nov 12, 2017 7:14 pm

How can you tell when a molecule is going to be T-shaped vs. whether it will be trigonal pyramidal or planar? Do you have to draw them differently or you can somehow just tell with the formula?

Srbui Azarapetian 2C
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Joined: Thu Jul 13, 2017 3:00 am
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Re: T-shape vs. trigonal

Postby Srbui Azarapetian 2C » Sun Nov 12, 2017 7:40 pm

A T shape has 3 bonds, and 2 lone pairs. An example of this is ClF3.
However, a trigonal planar shape has 3 bonds and 0 lone pairs. An example is BF3.
A trigonal pyramidal shape has 3 bonds and 1 lone pair like NH3.

I think the key difference here is the lone pairs.

Jonathan Tangonan 1E
Posts: 50
Joined: Sat Jul 22, 2017 3:01 am

Re: T-shape vs. trigonal

Postby Jonathan Tangonan 1E » Sun Nov 12, 2017 7:50 pm

Yes the difference is going to be the difference between the arrangement of the electrons and the regions of the high electron density and the number of lone pairs around the central atom. With a molecule with an arrangement of AX3E2 where there are five regions of high electron density and 2 lone pairs surrounding the central atom there will be a T-shape. This is also true for a molecule with the arrangement with AX3E3 will also result in a t-shape. For the most part, recognizing what molecule shape a molecule will have is going to be understanding the electron arrangement and also understanding what shape results based on the number of lone pairs surrounding the central atoms and where they are removed from.


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