Chemical Bonding: CH₃CN Lewis Structure

Drawing the Lewis Structure for CH₃CN

Viewing Notes:

• There are a total of 16 valence electrons in the CH₃CN Lewis structure.
• The CH₃CN chemical formula gives you a strong hint that CH3 will be attached to the central atom.
• Carbon (C) is the least electronegative atom and goes at the center of the CH₃CN Lewis structure.
• With CH₃CN you'll need a triple bond between the Nitrogen (N) and the Carbon (C) atoms (not the CH3 carbon atom).

Transcript: Let's do the CH3CN Lewis structure. For CH3CN we have 4 valence electrons for the Carbon plus 1 for the Hydrogen (we have 3 Hydrogens) plus 4 for the other Carbon and then 5 for that Nitrogen, giving us a total of 16 valence electrons. Carbon's the least electronegative, so that's going to go at the center. We'll put the other Carbon here and then the Nitrogen on this side. We can tell by the way it's written, that the CH3 means we're going to have Hydrogens around this Carbon right here, and the Nitrogen will be here on the other side.

So we have 3 Hydrogens around this Carbon here. We have our central Carbon, and then we have our Nitrogen over here. We'll put 2 electrons between atoms to form chemical bonds. We've used 6, 8, 10; and then around the outside, 12, 14, and we've used all 16 valence electrons right now that we started with. All of the atoms in the CH3CN Lewis structure have full outer shells except Carbon, which only has 4. Remember, Hydrogen only needs 2 for a full outer shell.

We can take 2 valence electrons from the Nitrogen here and move it to the center to form a double bond. Now Nitrogen still has 8 but Carbon has six, so we're getting close to an octet for Carbon. Let's move 2 more electrons here and share them with the Carbon. By forming that triple bond, we see that Nitrogen has 8 valence electrons and the Carbon has 8 valence electrons. We've only used 16 valence electrons that we started with.

So that's the Lewis structure for CH3CN. I'm Dr. B., and thanks for watching.