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Ch.10 - Chemical Bonding I: The Lewis Model

Chapter 10, Problem 67

How important is the resonance structure shown here to the overall structure of carbon dioxide? Explain.

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Welcome back everyone in this example. We need to choose the statement that describes the importance of resonance structure shown to the actual structure of sulfur dioxide. So recall our formula for sulfur dioxide is a neutral molecule and it's S. 02 with no net charge. We have a net neutral charge here. So let's write that down net neutral charge, meaning we have a net charge of zero. So we are given this structure below and were given the below statement and they're considering resonance hybrid. So what we want to recognize is that there are multiple ways we can draw our sulfur dioxide molecule. And according to the prompt, we're given this structure. We need to check whether this has a net neutral charge or a net charge of zero. So we're going to need to recall our formula for calculating formal charge for every atom in this lewis structure given. And we would recall that we would take our valence electrons for our selected atom in the structure subtracted from our non bonding electrons for that atom. And then subtracted from that our bonding electrons in our for our atom in our structure. And so looking at our first atom here, we have oxygen. Recall that oxygen in our periodic table is located in group six a corresponding to six valence electrons. And so we can count a total of 12. So 123 and then 45 valence electrons on this oxygen atom. Again recall that in our Covalin bonds here because these are two nonmetal atoms in these covalin bonds. We have a single valence electron contributed to each of the atoms that it's connected to. And that's why we count 12345 valence electrons on this oxygen atom on the left hand side. And so as we stated, oxygen wants six valence electrons for itself to be stable with a formal charge of zero. However, we only have five and that would leave us with a difference of being short of one more valence electron and that would give us our formal charge of plus one for this oxygen atom. Moving on to our sulfur atom in the center, we recall on our periodic table that sulfur is located in also group six. A meaning it also would prefer to have six valence electrons on itself in a structure. And so we can directly count a total of one, 234 valence electrons directly attached to this sulfur atom which are all shared in Covalin bonds with these two oxygen atoms. And so we would be short of a total of two valence electrons, meaning we have a formal charge of plus two for this sulfur atom. And lastly we have one more atom to calculate formal charge for. So looking at this oxygen atom, we can directly count a total of one, 234567 valence electrons directly attached to this oxygen atom. As we stated, oxygen prefers to have its six valence electrons in a structure, meaning that this oxygen atom is unstable And has one extra electron, which is why we counted seven. And that is also given to us by its formal charge of -1. Because we recall a minus charge means we have extra electrons. And in this case we have just one extra electron. And so if we were to calculate our net formal charge for this molecule, We would say that we have a total of plus one Which we add two plus 2 from our formal charge of sulfur. And then we would subtract one. And that would give us a formal net charge for this given structure being plus two. And so our net formal charges plus two for a given structure. But as we stated, sulfur dioxide has a net neutral charge according to its formula, meaning it has a net charge of zero. And so we would consider this given structure in the prompt because it has a net charge of plus two, it's a charged ion here. It's not going to be a resonant structure contributor. So it's a plus to net charge for this structure. So therefore it's not a resonance contributor To neutral S. 02. And so that means that we can confirm that the only correct choice to complete this example is going to be choice D. It is not a contributor to the resonance hybrid because our residents hybrid for sulfur dioxide should all have neutral formal charges. Net for the molecule. So D is our final answer. I hope everything I reviewed was clear. If you have any questions, leave them down below and I'll see everyone in the next practice video.