s-character of hybrids

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Jessica Chern 1H
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Joined: Sat Jul 09, 2016 3:00 am

s-character of hybrids

Postby Jessica Chern 1H » Tue Nov 01, 2016 12:25 pm

This is referring to the homework question 4.43. What does it mean by the s-character of the hybrids?

Posts: 21
Joined: Sat Jul 09, 2016 3:00 am

Re: s-character of hybrids

Postby Amber_Candelaria_1D » Tue Nov 01, 2016 3:23 pm

Hi, this was answered in a previous post:

"Answer: s-character is the contribution of sigma type bond in a hybridization: sp3 = 25% s-character, 75% p-character sp2 = 33% s-character, 66% p-character sp = 50% s-character, 50% p-character The more s-character a bond has, the stronger and shorter the bond is. so an sp-sp bond is strongest, and sp3-sp3 bond is weakest.

The bond angle of sp3 is 109.5, sp2 is 120 and sp is 180. An sp orbital is half s character, sp2 is 1/3 s character and sp3 is 1/4 s character, so increasing the s character corresponds to increasing the bond angle.
Another way to think about it is that you want to keep all of the orbitals of the same shape as far apart as possible (typically we would actually say that we want them to overlap as little as possible). Recall that when you hybridize one s and one p orbital, you get two sp orbitals, similarly you can mix two p and one s to get three equivalent sp2 orbitals. It turns out that the best way to keep two orbitals from overlapping much is to put them on opposite sides of the atom (sp - 180 degrees) keeping three of the same orbital apart results in a trigonal planar type structure (sp2 - 120 degrees). This is a little bit of why the angles increase as you increase s character."

Hope this helps!

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