Video: Drawing a Lewis Structure for Carbon Dioxide (CO₂)

Which of the following is the correct Lewis structure for CO₂? [A] Choice A [B] Choice B [C] Choice C [D] Choice D [E] Choice E

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Video Transcript

Which of the following is the correct Lewis structure for CO2?

The first step to draw a Lewis structure is to determine the number of valence electrons our compound has. We can determine the number of electrons each atom has by its position in the periodic table. Carbon has four valence electrons, and oxygen has six valence electrons. And we have two of them in CO2. This gives us a total of 16 valence electrons.

Our next step is to place our atoms and connect them with single bonds. We should put the atom that needs the most electrons to complete its octet in the center. This will generally be the one with the least number of valence electrons. In this case, it’s carbon. Each single bond contains two electrons, one from carbon and one from oxygen. Since we’ve drawn two single bonds in, we’ve already added four electrons to our structure. So there’s 12 electrons that still need to be placed.

Our next step is to distribute the remaining electrons so that each atom has a full octet, which is eight electrons. And we’re gonna start with the atoms on the outside of the structure with the terminal atoms. If we distribute our remaining 12 electrons, we get this structure before we run out of electrons to distribute. But carbon still doesn’t have a full octet. If this happens, we can form multiple bonds by using the lone pairs from the terminal atoms. So we can get rid of one of the lone pairs on oxygen and form a double bond between one of the oxygens and the carbon.

Now that we formed a double bond between one of the carbons and the oxygen, carbon still does not have a full octet. So let’s form a double bond between the other oxygen and the carbon. Now, each atom in our structure has a full octet. So this is the correct Lewis structure for CO2. This matches answer choice (B), which is the correct Lewis structure for CO2.

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