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.
