Figuring Out Bond Angle

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

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Joined: Wed Sep 18, 2019 12:19 am

Figuring Out Bond Angle

Postby Ananta3G » Tue Nov 19, 2019 10:24 am

Hello! How does one figure out the bond angle of a certain molecular geometrical shape? I know you can find it based on what kind of shape it is ie linear = 180 degrees, but how do you know when it is slightly more or less than the typical/definitional bond angle given by the general shape? ie sometimes the answer is "slightly less than 120 degrees" and not 120 degrees. Thanks!

Wendy 1E
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Re: Figuring Out Bond Angle

Postby Wendy 1E » Tue Nov 19, 2019 10:32 am

If the central atom has lone pairs, it will cause more electron-electron repulsion, which will result in a molecule having a bond angle that is smaller than usual (i.e. less than 120 degrees). You can think of this as if the electrons are "pushing away" the other bonds, which results in a smaller bond angle. For instance, the lone pair in a bent-shaped molecule, "pushes" away the other bonds, which results in a bond angle of fewer than 120 degrees between those bonds.

Sarah Nichols 4C
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Joined: Sat Aug 24, 2019 12:18 am

Re: Figuring Out Bond Angle

Postby Sarah Nichols 4C » Tue Nov 19, 2019 10:40 am

When there is a lone pair, it has stronger repulsion than an atom, so it will force the atoms in the molecule closer together and slightly decrease the angle
This will also happen if one of the atoms is larger than the others

Montana James 4G
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Joined: Wed Sep 18, 2019 12:21 am

Re: Figuring Out Bond Angle

Postby Montana James 4G » Tue Nov 19, 2019 11:21 am

Also you can't find out quantitatively how much smaller the distorted angle is, you can only determine that it is slightly smaller.

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