Question

How can I draw the Lewis structure for CO?

Answer 1

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: C-O.

3. Draw a trial structure by putting electron pairs around every atom until each gets an octet. In this editor, I will have to write it as :::C-Ö::

4. Count the valence electrons in your trial structure (14).

5. Now count the valence electrons you actually have available. 1 C + 1 O = 1×4 + 1×6 = 10. The trial structure has four extra electrons.

6. Draw a new trial structure, this time inserting one double bond for each extra pair of electrons : C≡O.

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

8. Calculate the formal charge on each atom :C⁻≡O⁺:

9. The “best” Lewis structure is usually one that has the fewest formal charges. We could draw a structure like :C=Ö: This has no formal charges, but the C atom does not have an octet.

Neither structure is "good", but the better structure is the first one.