Assign formal charges to the atoms in the following structures. W...

Question

Assign formal charges to the atoms in the following structures. Which of the two do you think is the more important contributor to the resonance hybrid? (a)

(b)

Accepted Answer

Welcome back everyone. We need to use formal charges and identify the resident structure that contributes the most to the hybrid. So we're going to recall a few facts. We're going to recall that structures uh, structures that contribute the most to the resonance hybrid. Or going to have the following preferences where we have atoms in the structure with full octet. So they're likely bonded to their bonding preference. Or they just in general have a full octet. We have negative and sorry, we have negative charges on the most electro negative atoms and positive charges on the most electro positive atoms. And then we have minimum formal charges. And then lastly we have the least amount of charge separation. So looking at choice A we would recognize that we have a plus one charge on this carbon atom which has three bonds, meaning it has +246 electrons around itself. And so this carbon does not have a full octet. However, carbon compared to all the other atoms in this structure, outside of hydrogen is the most electoral positive atom. And so it will therefore handle the positive charge. Well, however, we're going to rule out choice A because carbon does not have a full octet. And so because of that fact it's not going to contribute much to the resonance hybrid. So moving onto choice B, we note that we have a plus one formal charge on this oxygen atom here where it has a total of two of three bonds contributing six electrons and then we have a lone pair on the oxygen to complete its octet for eight electrons surrounding the oxygen atom. However, we want to recall that based on our election negativity trend on the periodic table, which increases towards the top right of our periodic table. We would recognize that oxygen is the most electro negative atom here in the structure, but it bears this plus one formal charge. And so it does not handle this positive charge well. And so we want to compare this to choice C. To see if it might work out better as contributing to resonance. So looking at choice, see we have our nitrogen atom now with a plus one formal charge where it has four bonds to itself, meaning it has +2468 electrons surrounding itself. So it does have a full octet where we also have a full octet with oxygen. So apologies for not noting that down. But again, we stated that that is from the three bonds and the lone pair on oxygen. So we have that fact match matching between choices B and C. But now from this plus one charge. And based on our election negativity trend, we recognize that nitrogen is less electro negative than oxygen. And so therefore nitrogen handles the positive charge best because it's a bit more electro positive than than oxygen would be. And so due to this fact, we would rule out choice be meaning that choice C would be the best answer for the structure that would contribute most to the resonance hybrid. I hope that everything I explained was clear. If you have any questions, please leave them down below and I'll see everyone in the next practice video.

Assign formal charges to the atoms in the following structures. Which of the two do you think is the more important contributor to the resonance hybrid? (a) (b)

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Assign formal charges to the atoms in the following structures. Which of the two do you think is the more important contributor to the resonance hybrid? (a)
(b)