Draw Lewis dot structures for each hypothetical molecule shown below, using the correct number of valence electrons for each atom. Determine which molecule makes sense because each atom has a complete valence shell, and each bond has the correct number of electrons. Explain what makes the other molecule nonsensical, considering the number of bonds each type of atom can make.

Question

Draw Lewis dot structures for each hypothetical molecule shown below, using the correct number of valence electrons for each atom. Determine which molecule makes sense because each atom has a complete valence shell, and each bond has the correct number of electrons. Explain what makes the other molecule nonsensical, considering the number of bonds each type of atom can make.

Accepted Answer

Hello. All our next problem says identify which of the following molecules is nonsensical hint, draw lewis dot structures and then predict. So we're given four answer possibilities. Skeletal structures with the bonds indicated between the atoms. So we're going to use a lewis dot structure to figure out which one does not make sense. So we're going to think about each of these different atoms and how many electrons it has in its outer shell, the valence electrons. So carbon we recall has four and its outer shell needs eight to be full. So it's gonna ideally want eight electrons around it. We've got hydrogen that's a little guy with only one electron because hydrogen only has one only at the first energy level. Its outer shell only has an s orbital with space for two electrons. So it only needs two and its outer shell oxygen has six valence electrons. So it only needs two more to have a full complement of eight. Which is why oxygen is so electro negative. Now let's look at our structures choice a We're gonna start by giving each carbon it's four valence electrons in this case these first two carbons are participating in four single bonds. Now this last carbon has two single bonds here but it's got a double bond to the oxygen atom. So it's sharing two electrons with the oxygen. Now we'll go to our hydrogen atoms and give them each their single electron in this case they are participating in single bonds with carbon atoms. And finally oxygen with its six. We've got two out of two electrons participating in this double bond that leaves four more which are gonna hang out here in two lone pairs, oxygen being electro negative more so than carbon is going to be quite happy with those lone pairs hanging out there. So now it's a double check that each atom here is happy with a full outer shell. We see our hydrogen participating in single bonds here, each with two shared electrons. Then our first carbon has got four single bonds giving it eight, The next carbon, four single bonds. And this final carbon here, two single bonds and then a double bond with oxygen. We're sharing four electrons, giving it a total of eight. And finally our oxygen, four electrons in this double bond and four more from the two lone pairs. So structure a here is perfectly fine. So we can eliminate that as our answer. Since we're looking for a structure that doesn't make sense. I'm just gonna scroll up a little just to make it a little easier to label this structure down below. We're gonna give our carbon. Its four electrons go to our next carbon and it's got two single bonds. And then it's sharing two electrons with oxygen and a double bond. I'm gonna go to our hydrogen and give them their single electron there. And then finally our oxygen's and we've got one oxygen over here participating in a bond with hydrogen as well as carbon. Oxygen has two single bonds, leaving four more electrons. So again, that will be in the form of two lone pairs. And the end oxygen shares two electrons in a double bond and then has two lone pairs. So let's double check our Outer shelves. The hydrogen each with two. Then this oxygen has two single bonds and then the two lone pairs giving it eight. This middle carbon, four single bonds and the final carbon has two single bonds and this one double bond giving it a total of eight and the final oxygen, the one double bond and two lone pairs. So structure be also totally fine. Let's eliminate that. Now we'll go to structure C and again give our carbons. Therefore, we'll label us out of carbon here. Now let's go to the central carbon. It has two single bonds. We'll put those on there and then a sharing two electrons in the double bond with oxygen. Let's go to our hydrogen. They're here sharing in single bonds with carbon. And finally our oxygen in green. It's got it's double bond with carbon and then it's two lone pairs. So again, quickly look at our bonds. Check for full outer shells. Here's our hydrogen with their single bonds to each. We've got our carbon on the end four single bonds giving it eight On the other end carbon with four single bonds. And in the middle we've got our carbon with two single bonds and the one double bond, The oxygen with the double bond and two lone pairs. So see also find not our answer. So we've only got one choice left. But let's just double check that that indeed is an incorrect structure. Start with our carbon and it's four electrons. And let's move on to hydrogen. So we move along here, one electron each. And now we come to our problem. We have a hydrogen in a central position here and that shows that participating in two single bonds, but hydrogen only has one electron to donate. So it will not form two bonds. Therefore, structure D. Does not make sense. And structure D therefore must be our correct answer to this problem. Since, as we recall from above, we wanted a structure that did not make any sense. See you in the next video.

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Key Concepts

Lewis Dot Structures

Valence Electrons

Bonding and Molecular Stability