Resonance Structures in 2F.3

[Alexa Mugol 3I]

For 2F.3, it says that SO2 would have 2 sigma bonds and 1 pi bond, but there is also a resonance structure that has 2 sigma bonds and 2 pi bonds. Would either answer for either resonance structure be correct?

[Ryan Narisma 4G]

Hello Alexa Mugol 3I! To answer your question, which resonance structure are you referring to? The lewis structure for SO2 would be S as central atom with a single bond between S and one of the Oxygens and a double bond between the S and the other Oxygen atom with a lone pair of electrons on the S atom. This lewis structure has 2 sigma and 1 pi bond. I am having trouble picturing the resonance structure to which you are referring.

[Alexa Mugol 3I]

Hello Alexa Mugol 3I! To answer your question, which resonance structure are you referring to? The lewis structure for SO2 would be S as central atom with a single bond between S and one of the Oxygens and a double bond between the S and the other Oxygen atom with a lone pair of electrons on the S atom. This lewis structure has 2 sigma and 1 pi bond. I am having trouble picturing the resonance structure to which you are referring.

Here are the two resonance structures for SO2:

I believe the second one is more stable since the formal charges for all the atoms are 0, but would identifying the sigma and pi bonds for first one still be correct even though it's less stable?

[Anisha Chandra 1K]

I was also confused about this. On the test, should we be drawing all resonance structures or just the most stable structure?

[Diana Chavez-Carrillo 2L]

Based on the type of questions that were given to us from some of the UAs the questions are phrased by saying "refer to the LOWEST ENERGY structure of..." or "refer to the MOST STABLE Lewis structure of..." So I am sure that the majority of the time we will be asked to draw and use the Lewis structure that is most stable and determine the sigma bonds and pi bonds based on the most stable structure. However, if we are not asked for the "most stable" structure like in 2F.3 then to play it safe I would draw out the resonance structures and their corresponding sigma/pi bonds.