Bond Angles with Different Atoms

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

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Ariel Fern 2B
Posts: 105
Joined: Fri Aug 30, 2019 12:17 am

Bond Angles with Different Atoms

Postby Ariel Fern 2B » Sat Nov 16, 2019 9:18 pm

I know it was mentioned in lecture briefly, but how and why do the bond angles change when an atom is replaced with a more electronegative one? For example, the bond angles in CCl4 VS. CCl3F1. Thanks!

Megan Cao 1I
Posts: 103
Joined: Sat Sep 07, 2019 12:18 am

Re: Bond Angles with Different Atoms

Postby Megan Cao 1I » Sat Nov 16, 2019 9:35 pm

for CCl4 the polarity of the Cl's for the electrons cancel each other out, which makes the molecule nonpolar and the repulsion of electrons from each atom equivalents. for the CCl3F molecule, the bond angle will no longer be 109 degrees, but instead a bit less. this is because the electronegativity of the Fluorine is greater than that of the Chlorine. this causes the polarities to no longer cancel each other out, thus making the molecule polar, due to fluorine's dipole.

Ashley R 1A
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Joined: Sat Aug 24, 2019 12:16 am

Re: Bond Angles with Different Atoms

Postby Ashley R 1A » Sun Nov 17, 2019 1:47 am

This concept can be applied to the opposite case when we compare CCl4 with CCl3Br

Because Br is less electronegative than Cl, the bond angles of the C-Cl bonds will be slightly greater than 109 degrees. Thus, making the CCl3Br molecule slightly polar as the individual dipole moments no longer cancel each other out due to differences in electronegativity.

805422680
Posts: 103
Joined: Sat Sep 14, 2019 12:16 am

Re: Bond Angles with Different Atoms

Postby 805422680 » Sun Nov 17, 2019 2:15 am

CCl4 is a non-polar molecule as the dipole moments of each of the C-Cl bonds cancel each other out, as they are in exactly opposite directions. However, for the molecule CCl3F, there will be a dipole moment generated in the direction of the fluorine atom, due to its high electronegativity. Bond angles will be a little less than 109.5 degrees for the C-F bond, due to the large size of the chlorine atoms and the additional space they require, the chlorine atom forces the C-F bond to be distorted.

Ruth Glauber 1C
Posts: 100
Joined: Wed Sep 18, 2019 12:20 am

Re: Bond Angles with Different Atoms

Postby Ruth Glauber 1C » Sun Nov 17, 2019 9:35 am

Does anyone have another example to illustrate these explanations?


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