Resonance Between Two Atoms

Π Bond Between Two Atoms

Molecules that have a π bond between two different atoms will exhibit resonance, provide the atoms are different, having different electronegativities. They have the following general structure.

You will encounter this pattern many times in organic chemistry. This resonance typically indicates that the carbon connected to Z is deficient in electrons. You should be able to draw the resonance hybrid for these.

Take note of the following

Take Note

Notice how the charge on the O or N increases by -1 in going from the left to right.
The charge on the carbonyl carbon (C) decreases by 1 in going from the left to right.
Same number of electrons on left as right.
Charge is conserved on the left and right sides (i.e. the net charge does not change).
No atoms ever move.