Confusion on Potential Resonance Structure Diagram

[Yu Jin Kwon 3L]

Hello!

I remember seeing Lewis structures like the one I attached below on Dr. Lavelle's lectures, but I don't exactly remember why there are dashed lines and what the dashed lines represent. I feel like it had to do with resonance structures, which is why I am uploading this inquiry here. I also remember Dr. Lavelle saying something about how the bonds of the actual molecule's Lewis structure are "in-between" something but I don't exactly recall what it was and what the significance of this was. Can someone explain what the dashed lines represent and what the "in-between" is talking about?

Thank you!!

[Anil Chaganti 3L]

Hi!
So basically for resonance structures, we regularly represent them by drawing multiple structures with different locations of the double bond. However, in reality, the bond length is distributed equally throughout the molecule as no particular atom has a double bond over a single bond. Therefore, the dashed lines represent somewhere in between a single and double bond that is distributed throughout the molecule.

[Giselle Granda 3F]

Hello! I am not sure about the "in-between," but I believe that the dashed line represents a partial bond character due to resonance/delocalization of electrons.

[Stuti Pradhan 2J]

In this diagram, the double bond between the nitrogen and the oxygen can technically be between the nitrogen and either oxygen, which causes resonance. When there is resonance, it is not that there is one set of double bonds and another single bond, but instead, both nitrogen-oxygen bonds are in between a nitrogen-oxygen double bond and a nitrogen-oxygen single bond. You can also think about this in terms of length, because the actual bond length of the nitrogen-oxygen bonds in this molecule will be between the lengths of a nitrogen-oxygen double bond and a nitrogen-oxygen single bond. The electrons in this situation are delocalized, so they are not associated with any covalent bond, therefore creating a bond that is in between our idea of a double and single bond, as there is no distinct single or double bond present.

Hope this helps!

[Jayasree Peri 2J]

Hi!
I'm not exactly sure about the dashed lines in this specific case, but I believe that you're right about them representing resonance. The "in-between" is essentially referring to the fact that when there is resonance, the bond length is in between two whole numbers. For example, when there's resonance where a certain bond can either be a single or double bond, the actual bond length will be somewhere in between the length of a single bond and the length of a double bond.

[Evelyn Silva 3J]

The dashed lines in the picture tell us that the actual structure is a resonance hybrid. Because the electrons are delocalized, the double bond character is spread across both of the O bonds. Therefore, the length of both bonds is in between a single and double bond (it's not exactly either one) and this is shown with the dashed lines on both sides.

[Katie Nye 2F]

The dashed lines are present when the structure allows for resonance. It is representative of the fact that the average bond length for this structure is 1.5 because the double bond and the single bond have the potential to be in either place.