Why T-shape?

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Alexa Mugol 3I
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Joined: Sat Aug 17, 2019 12:17 am

Why T-shape?

Postby Alexa Mugol 3I » Tue Nov 19, 2019 7:53 pm

Why is an AX3E2 molecule T-shaped? I thought it would be trigonal planar so that the lone pair electrons are opposite from each other. Why would the lone pair electrons be next to each other?

Hiba Alnajjar_2C
Posts: 108
Joined: Fri Aug 09, 2019 12:17 am

Re: Why T-shape?

Postby Hiba Alnajjar_2C » Tue Nov 19, 2019 8:00 pm

With trigonal bipyramidal structures, lone pairs are preferred to be in the equatorial position rather than axial (above/below), since there is less repulsion if you put the lone pair in the equatorial position. Therefore, you would have one atom and two lone pairs bound in the equatorial plane, while there would be 2 atoms bound in the axial position. Therefore, the structure resembles a T, hence its name. Hope this helps!
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Cooper Baddley 1F
Posts: 100
Joined: Wed Sep 18, 2019 12:19 am

Re: Why T-shape?

Postby Cooper Baddley 1F » Tue Nov 19, 2019 8:01 pm

It is T-shaped as you are having the electron pairs occupy the equatorial spots in order to reduce the effect they will have on the bonds. In doing this you are left with one equatorial and the top and bottom leading to T-shaped.

Daniel Honeychurch1C
Posts: 109
Joined: Thu Jul 11, 2019 12:15 am

Re: Why T-shape?

Postby Daniel Honeychurch1C » Tue Nov 19, 2019 8:01 pm

When atoms are replaced by lone pairs to make a T-shape, the atoms are from the equatorial positions because these atoms had a bond angle of 120 degrees. The axial atoms are not replaced because those atoms are only 90 degrees from the equatorial atoms. This maximizes the distance between the lone pairs and the bonded atoms.

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Joined: Sat Aug 24, 2019 12:17 am

Re: Why T-shape?

Postby SarahSteffen_LEC4 » Tue Nov 19, 2019 8:03 pm

The T-shape allows the two lone pairs of electrons to be farthest apart if they occupy two of the three equatorial positions. If they were to occupy axial positions, there would be great repulsion by the electrons.

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