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Discussion in 'DAT Discussions' started by HumanElement, Jul 2, 2008.

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  1. HumanElement

    HumanElement 2+ Year Member

    Jun 22, 2008
    ICl3. Correct answer is T-shape - not trigonal planar. Why?

    Can someone explain why ICl3 takes shape of T rather than planar? I know it is a T because of the 2 pair of non-bonding on the side of the plane. Wouldn't it be better or more favorable position if the lone pairs are on top and bottom and the 3 Cl on the horizontal plane?
    Last edited: Jul 2, 2008
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  3. TeachME

    TeachME 7+ Year Member

    Mar 3, 2008
    Well since there is only one set of lone pairs for Iodine, it can only be at the top or the bottom or left or right. Either way it still comes out to a T-shape no matter where you put the lone pairs. I guess it is the norm to put it at the top and then the bottom and so on and so forth. Just mentally rotate the molecule. Hope this helps.
  4. HumanElement

    HumanElement 2+ Year Member

    Jun 22, 2008
    There are 2 lone pairs and 3 shared around the I.

    For example in this pic. The lone pairs would be at the big ball and tiny ball space while the Cl would be at the other medium ball. The result would end in T-shape.

    I was thinking why can't the Cl position at Big ball, tiny ball, and the medium ball that are in same horizonal plane and the lone pairs stay on top and on bottom. In the latter configuration, it would result in a plane. My bad, I was thinking of plane earlier instead of linear since there are 3 Cl. Wouldn't it be better this way since they are all equal space apart rather than uneven distribution in T-shape configuration?
  5. Maygyver

    Maygyver 5+ Year Member

    Jun 13, 2008

    It helped me to look at the diagram here http://en.wikipedia.org/wiki/VSEPR.

    I think no matter where you take the electrons from it will result in a T-shape. I find the easiest way for me to do VSEPR is just to memorize that diagram because some of it is slightly counter intuitive. I hope this helps.
  6. Maygyver

    Maygyver 5+ Year Member

    Jun 13, 2008

    I actually had the same problem when I first learned VSPER. I forget the reasoning behind the T-shape. :-\ I'll try to look into it some more.
  7. HoangDDS

    HoangDDS 2+ Year Member

    Apr 20, 2008
    San Jose
    It wouldn't be trigonal planar because because of exactly what you've said. The two lone pair is gonna cause replusion. Plus trigonal planar is AX3. While ICl3 is AX3E2 which is T shaped. Just basically following the VSPR rules.

    (X = surrounding atoms, E = lone pair)

    It can't be have 3 Cl on the same plane with one lone pair on top and bottom. There will just be too much electron repulsions between the unpaired electrons of Cl and the I 's lone pairs.
  8. AdaAda87

    AdaAda87 2+ Year Member

    Apr 10, 2008
    Why is it trigonal pyramidal?

    Shouldn't the 3 clorines be on the bottom, and then the lone pair be on the top?

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