Determining Resonance

[Samantha Rundle 3K]

Is there a quicker way to determine if there are resonance structures, other than calculating formal charge? If so, how?

Thanks!

[HoganFenster2E]

I think that you usually need to calculate the formal charges. It is a good way to check your work too, especially if the compound has a negative or positive charge, because it must have that charge. Also, a little shortcut is (I'm not sure how helpful this is) that whenever you have an Oxygen with a double bond and two lone pairs the charge will always be zero. You can also figure out when atoms will have a formal charge of zero and just memorize them. Thats what I do and it goes a little quicker.

[Jessica Chern 1H]

Also, if an atom is double bonded to one atom of a certain element X as well as single bonded to more atoms of that same element X (that aren't also bonded to anything else), there will be resonance.

[Wang_Pong_Chan_1L]

First makes the octet on each of the elements, then using the electrons needed figure out the double bonds, which will show you whether there is resonance or not.