2F. 15 General Pattern?

[Jordan Ziegler 2J]

2F. 15 reads: "Noting that the bond angle of an sp3 hybridized atom is 109.5 and that of an sp2 hybridized atom is 120, do you expect the bond angle between two hybrid orbitals to increase or decrease as the s-character of the hybrids is increased?"

My first question is: what is the s-character of the hybrids?

My second question is: are there any relationships between bond angle we need to know as hybridization order increases? (ie. sp2 --> sp3 --> sp3d ...)

[Ashley Wang 4G]

Hi,

Since hybrid orbitals are a blend of atomic orbitals, I imagine the "s-character" is the characteristic of the hybrid orbital that the s-orbital contributes to. For example, sp2 has more s-character than sp3 hybrid orbitals.

As for the second question, the most straightforward way I would approach it is the correlation between the VSEPR model and the hybridization scheme, which would tell you that increasing s-character increases the bond angles. I don't know if there's more to it that we need to know though.

If anyone has more to add, please do!

[Natalie Wang 1B]

I agree. I believe that s character is referring to the role of the s orbital in the hybridization. An sp2 hybridized orbital would have more s character than an sp3 hybridized orbital. And, as we know from molecular structures, a structure with sp3 hybridized orbitals (like a tetrahedral molecule) will have smaller bond angles than a structure with sp2 hybridized orbitals (like a trigonal planar molecule). Therefore, increasing s character increases the bond angle size.