finding resonance structures

[Natalie 3k]

Hi, I sometimes struggle with finding the resonance structures for certain molecules, does anyone have any tricks that help you easily make all the structures?

[Sophia Hu 1A]

Hi!

Typically for resonance structures, I first draw the best lewis structure, and then if it is possible to move a double bond in different positions without changing the location of atoms then there is a resonance structure.

You can also think, is there another way a different person would draw this molecule? For instance SO4 2-, if you draw it one way, you can also realize that another person may draw the ion another way and it would still be the correct Lewis structure. Or for Benzene, if you place the double bonds in a particular place, another person can place them in a different area and still have the correct structure.

I also sometimes think about it as shifting the bonds. Resonance occurs when there is are single and double bonds, and the double bond an be in various locations while still keeping the atoms in the same location. I just thinking about shifting the bonds in a clockwise motion, and if it is possible to do then there is resonance. However, there are also some structures like Sulfate, where the double bonds can be between adjacent oxygen or they can be on opposite oxygen and in this case shifting the bonds around the molecule would not be enough.

Overall, the best way is to think about resonance is asking if another person can draw the Lewis structure in a different way by manipulating the single and double bonds while keeping the atoms in the same place.

I hope this helps! Practice also definitely helped me recognize when there was resonance and when there wasn't.

[Angel More]

I struggle with this too! Sophia gave a lot of great tips. I think it's a lot of playing around with moving things and seeing what could work: changing double bonds to single bonds with electron pairs. Unfortunately there is no set steps on how to find resonance, but practice will help you get faster.

[Anna Yakura 2F]

Hello! Personally I just try moving the bonds around, and seeing if they will work. Seeing if there are other alternatives for bonds (a single, instead of a double) could also provide resonance structures (but may not be the most stable/plausible structure). Often times in the textbook problems, they include a structure that completely obeys the octet rule (if there is one), and a structure that takes advantage of octet expansion, etc. Hope this helped!

[Lesly Lopez 3A]

Hi!

This is a hard concept for me too because I feel like I can never do it right lol. I draw the one that is the best and then from there I simply try to make either double or triple bonds. Still, you have to keep in mind that some of them will not be the most stable or even plausible. Make sure you follow all the rules, mainly the octet rule.

[Riya Sawhney 1C]

Hi! The big thing to remember is that electrons move around, but the atoms themselves do not. So I'll start by re-drawing the atoms in the same place, then seeing if I can either move around the location of a double bond, or if there is anywhere to add a double or triple bond. It is good to keep in mind which elements can have an expanded octet, and which elements (such as C, N,O...) can only participate in 4 bonds.