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Author Topic: PBr4- "see-saw" hybridization  (Read 1967 times)

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mingusaum

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PBr4- "see-saw" hybridization
« on: March 04, 2013, 04:24:43 PM »

Hello,

I am trying to figure out the hybridization for the PBr4- molecule, which I imagine has the see-saw geometry (correct me if I am wrong). Everybody says it is "sp3d," but which d orbital is hybridized exactly? What is the  symmetry (a, e, or t)? How is this different than the hybridization in the square planar geometry?

Thank you!
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Hunter2

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Re: PBr4- "see-saw" hybridization
« Reply #1 on: March 04, 2013, 10:33:43 PM »

Phosphorus has [Ne] 3s2 3p3. Now we add 3 Br and  1 Br-. 3 bring one electron and Bromide bring 2 electrons, so we can fill 3 s2 3p6 and 3 d2 This will give one new hybrid orbital sp3d2
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mingusaum

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Re: PBr4- "see-saw" hybridization
« Reply #2 on: March 05, 2013, 02:42:37 AM »

Sorry, this is incorrect. PBr4- has 4 P-Br bonds and one lone pair, meaning 5 orbitals are involved in the hybridization (see http://sydney.edu.au/science/chemistry/~george/1108/ShapesOfMolecules.pdf or http://www.scribd.com/doc/78707220/Molecular-Geometry-Memorize-Shape for example).

So can somebody please answer my original questions of which d-orbital is involved in the hybridization, the symmetry, and how these differ from what happens in a square planar bond?
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Hunter2

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Re: PBr4- "see-saw" hybridization
« Reply #3 on: March 05, 2013, 06:29:54 AM »

What is incorrect. You have 10 electrons to put in, 5 from phosphorous 4 from the 4 Bromine and one negative charge. Each orbital can carry 2 Electrons means we need 5 of them so we have 1 s orbital 3 p orbitales and one d-Orbital to fill with the 10 electrons.
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mingusaum

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Re: PBr4- "see-saw" hybridization
« Reply #4 on: March 05, 2013, 06:51:12 AM »

Exactly right. This means sp3d hybridization, not sp3d2 as you said in your original post.

But again, this is not my question. If you have an answer to my original question, I would definitely appreciate it.
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Hunter2

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Re: PBr4- "see-saw" hybridization
« Reply #5 on: March 05, 2013, 08:31:07 AM »

I didnt catch your question. Which d orbital? There 5 existing. But nobody can tell which on it is. I think it doesnt matter pick one. LOL.
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mingusaum

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Re: PBr4- "see-saw" hybridization
« Reply #6 on: March 05, 2013, 09:16:56 AM »

It matters to me, that is why I asked. But thanks for your time!

Anybody else have an answer?
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mingusaum

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Re: PBr4- "see-saw" hybridization
« Reply #7 on: March 05, 2013, 03:35:36 PM »

Just to clarify, I think it might matter which d-orbital hybridizes due to symmetry reasons, but I could be wrong. If anybody has a rigorous answer as to which orbital it is (or conversely why all d orbitals are allowed by symmetry), I would really appreciate it!
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