Resonance Structures

[Chelsea Culi 3F]

How will we know if a molecule has a resonance structure? Will we have to check its formal charges every time?

[Mihir Sukhatme 1D]

The easiest way to notice if there is resonance is if there is a lack of electrons when trying to complete each atom to the octet rule. Usually, you will notice that you are a few electrons short and in that case, it's best to try turning some bonds to double bonds and if this works, the molecule has resonance.

[Amanda Tran 1D]

If a molecule's lewis structure can be drawn multiple ways and maintain the same energy, it will have a resonance structure. The structure for NO₃-, for example, has one double bond, that can be drawn in three different ways - each of those lewis structures would be a resonance structure.

[Amanda Pineda 3H]

A molecule has resonance if various bonds could be placed in different locations and still have the desired octets and molecular charge intact. Resonance is usually when you can place double bonds in multiple locations and still have the some molecule. Hope this helps!

[405716590]

If there is not an octet it is probably resonance, and then for other examples where this is not the case it is pretty easy to check formal charge so it isn't a bad thing to do every time.