How can I draw the Lewis structure for #CO_2#?

1 Answer
May 10, 2014

You follow a sequence of steps.


Here are the steps that I follow when drawing a Lewis structure.

1. Decide which is the central atom in the structure. That will normally be the least electronegative atom (#"C"#).

2. Draw a skeleton structure in which the other atoms are single-bonded to the central atom:

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3. Draw a trial structure by putting electron pairs around every atom until each gets an octet.

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4. Count the valence electrons in your trial structure (20).

5. Now count the valence electrons you actually have available. #1"C" + 2"O" = 1×4 + 2×6 = 16#.

The trial structure has four electrons too many.

We need to insert either a triple bond or two double bonds.

6. Draw new trial structures, this time inserting the extra bonds.

There are three possibilities:

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7. As before, add valence electrons to give each atom an octet:

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8. Calculate the formal charge on each atom.

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9. The “best” Lewis structure is one in which has the fewest formal charges.

The first structure has no formal charges, so the best Lewis structure for #"CO"_2# is