Bond Angles

(Polar molecules, Non-polar molecules, etc.)

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Jessica Li 4F
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Bond Angles

Postby Jessica Li 4F » Sat Nov 16, 2019 12:23 pm

For tetrahedral molecules (or of any shape really) like CHCl3 or POCl3 that are polar but don't have any lone pairs, why are the bond angles all 109.5 degrees (according to the solutions manual)? Would not the more polar atoms attached to the central atom push the other atoms away slightly more?

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Re: Bond Angles

Postby Chem_Mod » Sat Nov 16, 2019 12:29 pm

Not necessarily. All bonds, regardless of multiplicity (e.g. single bond, double bond) or polarity, all have the same amount of electron repulsion because they are all confined to the spaces between atoms. However, lone pairs cause more electron repulsion because they are not bonded to anything and have more room to move around, thus pushing down on the entire molecule and decreasing bond angles.

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Re: Bond Angles

Postby SajaZidan_1K » Sat Nov 16, 2019 12:41 pm

I would review the concept of repulsion Lavelle talked about in class. He lays out the parts of a molecule that cause repulsion. For instance, a lone pair causes repulsion and can cause two atoms to come closer together. This would decrease the angle between the atoms.

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Re: Bond Angles

Postby RobertXu_2J » Sat Nov 16, 2019 1:30 pm

all bonds have the same "push", because the space they occupy is between atoms. Lone pairs cause more push because they can move freely on the outskirts of an atom, and thus it has a wider area of effect and a stronger push.

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