If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:4:28

Video transcript

in the previous video we looked at the dot structure for sulphur dioxide 9 through out two resonance structures so the resonance structure on the left and the resonance structure on the right and some people disagreed with me and said that's not the dot structure for sulphur dioxide the dot structure for sulphur dioxide has sulphur with a double bond to an oxygen on the left and two lone pairs of electrons on that oxygen and the sulfur with a double bond to oxygen on the right and two lone pairs of electrons on that oxygen and then we have a lone pair of electrons on our sulfur so the advantage to this dot structure is we don't have any formal charges so the formal charge on sulfur is zero and the formal charge on both oxygens is zero and so this is a valid dot structure right there's nothing wrong with this dot structure it's fine if we look at sulfur if you look at sulfur we count up the electrons around sulfur here's 2 & 4 6 8 and then 10 so we have more than eight electrons around our sulfur so sulfur has an expanded valence shell so this is expanded we have more than eight electrons around it and that's okay to do because of sulfur is position on the periodic table Sulphurs in the third period so we have some D orbitals so we can have more than eight electrons around sulfur so that's fine so this should be a valid dot structure if we go back up here and we look at one of our resonance structures I'll take the one on the right we do have formal charges right which usually our goal is to minimize formal charges if we look at this sulfur right here and we count our electrons we have two four six and then two more for a total of eight so we have an octet of electrons around sulfur so for this resonance structure we have an octet of electrons but we have formal charges down here we have an expanded valence shell but we have zero formal charges so which version of sulfur dioxide is the correct one so in my opinion in my opinion they're both fine because for the first version right we'll draw two resonance structures and we put in put in our brackets and everything we are saying that the actual structure is a hybrid of our two resonance structures right so sulphur dioxide doesn't look like this it doesn't look like this it's a hybrid of our resonance structures so if we just think about bonds right and I drawn our bonds here the bond of sulphur to oxygen well if we look on the left let me use a different color here we have a double bond between sulphur and oxygen on the right we have only a single bond here so a hybrid of these two resonance structures would say that this bond is in between a single bond and a double bond so we could put a dotted line here like that and on the right our bond between sulfur and oxygen let's look on the right let me use a different color here I'll use green over here we have a single bond and over here we have a double bond so if we if we put in a dotted line right that bond is in between a single bond and a double bond so like that and experimentally both sulfur oxygen bonds have the same length which is what our hybrid shows us right our hybrid shows us the same length between our sulfur oxygen bonds so in my opinion it's fine to represent sulfur dioxide with these two resonance structures and I looked in several general chemistry textbooks and actually most of them most of them gave give you this as the answer so some of them give you this as the answer and in my opinion they're both correct sometimes you can only figure out the best way to do something like this by using quantum calculations right and that's just way too complicated for something that we're talking about both of them will tell you the shape of sulfur dioxide right both of them give you bent geometry around your sulfur and so we might change this depending on what teacher you have right so some teachers are extremely strict about minimizing all formal charges and so they might expect you to draw this version all right whereas other teachers are fine with with drawing resonance structures and thinking about a resonance hybrid so do whatever your teacher wants you to do but in my opinion both of these are correct and it's not really worth debating about too much
AP® is a registered trademark of the College Board, which has not reviewed this resource.