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Offline lokhtar

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Molecular hybridization Question
« on: September 20, 2008, 09:44:32 AM »
Hello,

I am having a lot of trouble understanding molecular hybridization theory.  For example, my book says that methane has sp^3 hybridization of carbon.

The way I understand it is hybridization is which molecular orbitals are shared between atoms, correct?  So if Carbon has an electron configuration of 1s^2 2s^2 2p^2, how can it have p^3 hybridization, if it doesn't even have that many p electrons.  I am probably missing something basic, but I'd appreciate any help.  I tried looking for tutorials online, but couldn't find any good ones.  I'd appreciate any help.

Offline Borek

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Re: Molecular hybridization Question
« Reply #1 on: September 20, 2008, 10:43:07 AM »
The way I understand it is hybridization is which molecular orbitals are shared between atoms, correct?

No, sp3 means you mix one s and three p orbitals of one atom.
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Offline Yggdrasil

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Re: Molecular hybridization Question
« Reply #2 on: September 20, 2008, 10:46:01 AM »
sp3 means that it hybridizes one 2s orbital and three 2p orbitals to create four sp3 orbitals.  The superscript 3 does not indicate 3 electrons as it does in the electron configuration.

Offline lokhtar

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Re: Molecular hybridization Question
« Reply #3 on: September 20, 2008, 10:59:15 AM »
So the reason it is a sp3 is because it has four bonds, and one of the electrons from the s orbital comes up to the p orbital so it can form a bond?

In that case, let me give you an example of

C-O-H

Now, the book says that the O has sp3 hybridization.  O has 6 valence electrons, two in the s shell and four in the p shell.  However, unlike carbon in the above example, this time oxygen only forms two bonds.  Why would it still be a sp3 hybridization?

Offline Yggdrasil

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Re: Molecular hybridization Question
« Reply #4 on: September 20, 2008, 11:53:25 AM »
Do you mean CH3OH?  AFAIK, there is no such thing as COH.

The hybridization of an atom is determined by the number of atoms bonded to the central atom PLUS the number of lone pairs on your central atom.  For example, in water (H2O), the central oxygen is bonded to two hydrogen atoms and has two lone pairs, giving a total of four regions containing electrons.  This makes the O in water sp2 hybridized.

Offline Astrokel

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Re: Molecular hybridization Question
« Reply #5 on: September 20, 2008, 12:45:44 PM »
This makes the O in water sp2 hybridized.
I guess it is a typo error, should be sp3.
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Offline lokhtar

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Re: Molecular hybridization Question
« Reply #6 on: September 20, 2008, 01:05:13 PM »
CH3-C---N

(C---N is a triple bond).

If I wanted the hybridization of the C atom, it would be that there are two atoms bonded to the central atom, plus zero lone pairs on the central atom, so it would be a sp hybridization?

Now, what would be the hybridization of the leftmost C atom in that molecule?  It has 3 Hydrogen and 1 Carbon attached to it, so since it has four, it is sp3?

So is that the only thing you look at to figure out the hybridization?  If an atom has two other atoms attached to it and no lone pairs, it would be a sp, with two atoms and one lone pair, it would be sp2, etc?  Does it matter if the atom in question isn't the 'central' atom of the whole molecule (like the example above)?

Offline lokhtar

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Re: Molecular hybridization Question
« Reply #7 on: September 20, 2008, 02:15:55 PM »
I guess what I said above is wrong, because apparently BF3 is sp2 instead of sp3.  If I have to add the number of atoms attached to the central atom plus the number of lone pairs on the central atom (since B has five valence electrons), wouldn't it be 3 Fluorine atoms + one lone pair on B = 4 so sp3 hybridization?

EDIT:  No, Boron has 3 valence because it is 1s22s22p1, so it would make sense.  So is my reasoning correct for the above post?

Offline Astrokel

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Re: Molecular hybridization Question
« Reply #8 on: September 20, 2008, 02:34:42 PM »
yes you are right BF3 is sp2 because of 3 atoms bonded to central atom boron and zero lone pair on it(3 + 0 = 3) the 3 equals to the sum of superscript of the spx, s has a superscript of 1.

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Offline macman104

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Re: Molecular hybridization Question
« Reply #9 on: September 20, 2008, 03:46:31 PM »
Yes, your reasoning is correct.  You just used incorrectly what you thought was Boron's lone pair count (you said 1 instead of 0).  If you used your reasoning with the correct lone pair count you would have seen that it did work!

Offline Yggdrasil

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Re: Molecular hybridization Question
« Reply #10 on: September 20, 2008, 05:08:44 PM »
This makes the O in water sp2 hybridized.
I guess it is a typo error, should be sp3.

You are correct.  Thanks.


Offline lokhtar

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Re: Molecular hybridization Question
« Reply #11 on: September 20, 2008, 05:21:43 PM »
This makes sense now.  Much obliged!

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