Molecular Shape

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

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Emily Orozco L4
Posts: 45
Joined: Fri Sep 28, 2018 12:29 am

Molecular Shape

Postby Emily Orozco L4 » Wed Nov 14, 2018 8:04 pm

One of the homework problems (#9 sixth edition) asks for the shape of ICl3, where iodine is the central atom. I thought the shape would be trigonal planar, but I see that the correct answer is t-shaped. What makes it t-shaped instead of trigonal planar?

Manya Bali 4E
Posts: 66
Joined: Fri Sep 28, 2018 12:23 am

Re: Molecular Shape

Postby Manya Bali 4E » Wed Nov 14, 2018 8:17 pm

ICl3 has 3 bonding pairs of electrons (I - Cl), and then the central atom, I, also has two lone pairs. As discusses in class, the electron repulsion of lone pairs and lone pairs is higher than that of a lone pair and a bonding pair which is higher than that of two bonding pairs. Because of these lone pairs and their electron repulsion, the bonding pairs of electrons and the Cl atoms are pushed closer toward each other, resulting in a t-shape (which I believe we will discuss more about during Friday's lecture). There are 5 regions of electron density (3 Cl atoms and 2 lone pairs), so it would not be trigonal planar. It would also not be trigonal bipyramidal because there aren't 5 bonding pairs.
Last edited by Manya Bali 4E on Wed Nov 14, 2018 8:17 pm, edited 1 time in total.

Kate Chow 4H
Posts: 61
Joined: Fri Sep 28, 2018 12:28 am

Re: Molecular Shape

Postby Kate Chow 4H » Wed Nov 14, 2018 8:17 pm

When you draw the Lewis Structure, you see that iodine has 2 lone pairs. Since iodine has 2 lone pairs, it makes it t-shaped instead of trigonal planar. Molecules that are trigonal planar don't have lone pairs on the central atom.

Hovik Mike Mkryan 2I
Posts: 95
Joined: Fri Sep 28, 2018 12:25 am

Re: Molecular Shape

Postby Hovik Mike Mkryan 2I » Wed Nov 14, 2018 8:21 pm

Hello,
I believe it is not tirgonal planar because of the two lone pairs that lie on the central Iodine atom. 3 Cl atoms have 21 electrons and 1 I atom has 7. Resulting in 28 electrons.
It would take 24 electrons to fulfill the Cl octets with I only having 6 electrons on it (the three bonding pairs). The remainder 4 electrons would go on the I so satisfy the octet.
The lone pairs cause repulsion resulting in the T shape instead of the trigonal planar. Hope this helped!

Tatum Keichline 2B
Posts: 64
Joined: Fri Sep 28, 2018 12:26 am

Re: Molecular Shape

Postby Tatum Keichline 2B » Wed Nov 14, 2018 8:22 pm

Lone pairs on the Iodine lead to repulsion making it t-shaped

Kimberly 1H
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Joined: Fri Sep 28, 2018 12:17 am
Been upvoted: 1 time

Re: Molecular Shape

Postby Kimberly 1H » Wed Nov 14, 2018 8:50 pm

If the lone pair-lone pair electron repulsions are the strongest, then why can't the two pairs be situated opposite each other, as in a trigonal bipyramidal shape? One lone pair on top and one on the bottom? Wouldn't this result in a molecular geometry of a trigonal planar shape?

Kelly Zhang 1L
Posts: 31
Joined: Fri Sep 28, 2018 12:18 am

Re: Molecular Shape

Postby Kelly Zhang 1L » Wed Nov 14, 2018 9:06 pm

If a structure has two single bonds and two lone pairs, is the shape of this bent?


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