Bond Angle Exceptions

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

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Bond Angle Exceptions

Postby rkusampudi » Sat Nov 11, 2017 9:20 pm

As I was reading the textbook, I noticed that many molecular shapes have bond angles that are different from what is expected of that shape. Is there any way to predict these exceptions or do they have to be memorized?
EX: the HOH bond angle

Ramya Lakkaraju 1B
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Re: Bond Angle Exceptions

Postby Ramya Lakkaraju 1B » Sat Nov 11, 2017 9:59 pm

The exceptions to the bond angles are caused by repulsion by the lone pairs of electrons. In lecture, Dr. Lavelle mentioned that we only had to know what the bond angles should be for most shapes and that we did not have to memorize the exceptions.

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Re: Bond Angle Exceptions

Postby RussellChin_3A » Sun Nov 12, 2017 11:32 am

When it gets to bond angles for structures that include lone pairs, we just have to know that the bond angle will be less than that of the expected one. For example, for a trigonal pyramidal, we only need to know that the bond angle that results from it, will be less than 109.5. This is because it would have a tetrahedral geometry, but the lone pairs would be pressing down on the bonding pairs which result in a slightly lower bond angle.

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Re: Bond Angle Exceptions

Postby 004734229 » Sun Nov 12, 2017 5:52 pm

I believe that a bond that is closer tot he nucleus will cause electron repulsion from the other atoms around the central atom which will cause a change in bond angles.

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