Video Transcript
The Lewis dot diagram for a covalent molecule is shown. Which of the following molecular structures corresponds to this Lewis dot
diagram?
This question is asking us to interpret this Lewis dot diagram, also known as a Lewis
dot structure. What does a Lewis dot diagram show? First, it shows the atoms present. We can see from the Lewis dot diagram that this molecule contains two oxygen atoms
and a carbon atom. Other ways to represent this compound that also show the atoms present include its
chemical formula, CO2, and its name, carbon dioxide.
The Lewis dot diagram is more informative than the chemical formula or the name
because it also shows the valence electrons of the atoms present. More specifically, it shows the bonding electrons shared between atoms, as well as
the lone pairs belonging to just one atom.
The molecular structure of the answer choices doesn’t show electrons but does show
covalent bonds. To bridge the gap between these two structures, we need to know that covalent bonds
represent a pair of shared electrons. Looking at the structure in the question, we can replace each bonding pair of
electrons with a covalent bond, forming two double bonds in total. The lone pairs, on the other hand, are not represented by bonds. In the kind of molecular structure shown in the answer choices, they are assumed to
be present but are not drawn.
If we carry out this transformation, we are left with the structure drawn in answer
choice (A), the correct answer. The structure from the question and the structure from answer choice (A) are
different ways of representing the same molecule, carbon dioxide.
So which molecular structure corresponds to this Lewis dot diagram? That’s the structure drawn in answer choice (A).
