## Angular vs. Bent

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

LBacker_2E
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### Angular vs. Bent

When we are determining the molecular shape of a compound that has a central atom with two bonded pairs and two lone pairs, is the name of this shape "angular" or "bent"? I think they are the same thing, if they are not what is the difference between the two? If they are the same which name does Dr. Lavelle prefer us to use?

Kristina Rizo 2K
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### Re: Angular vs. Bent

They mean the same thing, I think he said something in lecture about using bent, but the TA's won't mark it incorrect if you use either one.

Katie Kyan 2K
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### Re: Angular vs. Bent

Bent and angular are the same thing. We can use either one to name structures.

Micah3J
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### Re: Angular vs. Bent

How can we tell if the bond angle should be equal to a certain degree or less than the certain degree. An example of this can be ClO2+... The shape is bent, but I don't know how to tell that it is less than 120 degrees instead of just exactly 120 degrees.

Katie Kyan 2K
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### Re: Angular vs. Bent

Micah3J wrote:How can we tell if the bond angle should be equal to a certain degree or less than the certain degree. An example of this can be ClO2+... The shape is bent, but I don't know how to tell that it is less than 120 degrees instead of just exactly 120 degrees.

Generally a bond is equal to a certain degree when it is one of the parent structures (linear, trigonal planar, tetrahedral, trigonal bipyramidal, or octahedral) and all the atoms surrounding the central atom are the same. For example we say that the bond angles in a trigonal planar shape of this case are approximately 120 degrees. However when there are lone pairs, the bond angles become slightly less than the certain degree. This is because lone pair lone pair repulsion is greater than lone pair bonded pair repulsion. Thus, for shapes like trigonal pyramidal, we say that the bond angle is slightly less than 109.5 degrees.

Knowing the size/electronegativity of the atoms involved in the bonds can also influence the bond angle approximation. One example Dr. Lavelle gave in class was BF3 which has bond angles of approximately 120 degrees. Yet for BF2Cl, knowing that Cl is bigger than F would tell us that the F-B-Cl bond angles will be slightly greater than 120 degrees while the F-B-F bond angle will be slightly less than 120 degrees.

Micah3J
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Joined: Tue Oct 08, 2019 12:16 am

### Re: Angular vs. Bent

Katie Kyan 1B wrote:
Micah3J wrote:How can we tell if the bond angle should be equal to a certain degree or less than the certain degree. An example of this can be ClO2+... The shape is bent, but I don't know how to tell that it is less than 120 degrees instead of just exactly 120 degrees.

Generally a bond is equal to a certain degree when it is one of the parent structures (linear, trigonal planar, tetrahedral, trigonal bipyramidal, or octahedral) and all the atoms surrounding the central atom are the same. For example we say that the bond angles in a trigonal planar shape of this case are approximately 120 degrees. However when there are lone pairs, the bond angles become slightly less than the certain degree. This is because lone pair lone pair repulsion is greater than lone pair bonded pair repulsion. Thus, for shapes like trigonal pyramidal, we say that the bond angle is slightly less than 109.5 degrees.

Knowing the size/electronegativity of the atoms involved in the bonds can also influence the bond angle approximation. One example Dr. Lavelle gave in class was BF3 which has bond angles of approximately 120 degrees. Yet for BF2Cl, knowing that Cl is bigger than F would tell us that the F-B-Cl bond angles will be slightly greater than 120 degrees while the F-B-F bond angle will be slightly less than 120 degrees.

Thank you so much, that really helps a lot. Well explained. I appreciate it.