(Polar molecules, Non-polar molecules, etc.)
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A T-Shape is created when there is one central atom with two lone pairs and three bonded atoms. The shape comes from the electron repulsion of the lone pairs. Some examples are ClF3 and BrF3.
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Why wouldn't this be a trigonal planar shape with the electron clouds in the axial positions? Didn't we talk about the electron clouds wanting to be as far apart as possible to minimize repulsion and make the molecule more stable?
KDang_1E wrote:Why wouldn't this be a trigonal planar shape with the electron clouds in the axial positions? Didn't we talk about the electron clouds wanting to be as far apart as possible to minimize repulsion and make the molecule more stable?
I do not have a definite answer for this, but I like to look at it based on how many areas of electron density are surrounding the central atom. In this case it would be five which would correspond to the trigonal bipyramidal shape. If you were to take away two of the equatorial atoms of a trigonal bipyramidal you would get a t-shaped molecule. This is similar to what Professor did in class today, having people remove atoms from his model to reveal where the lone pairs would be. I believe he said that which electrons are taken away is based on the most stable structure with the least amount of large angles separating the atoms, but I am not 100% sure about this.
The reason why the molecule would not be a trigonal planar is because trigonal planar means that the bound atoms are about 120 degrees away from each other, but that would not make sense because there are 2 lone pairs which means there is very strong repulsion between the lone pairs and the lone pair and the covalent bonds. This repulsion would change the bond angles.
I also read in the textbook that most of the time, it is more stable to have equatorial lone pairs rather than axial pairs, which would explain how you get a T-shape from the trigonal bipyramidal electron arrangement of an AX3E2 molecule.
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