[bishiw]

Why isn't this a viable resonance structure?

[AWK]

What is the definition of a mesomeric structure?
Does the structure you draw meet the definition requirements?

[Babcock_Hall]

What you drew breaks at least one fundamental principle.

[bishiw]

What you drew breaks at least one fundamental principle.

Which one? I'm completely lost haha. I also meant to draw an oxygen with a + charge, not -.

[bishiw]

What is the definition of a mesomeric structure?
Does the structure you draw meet the definition requirements?

I meant to draw an oxygen with a + charge instead. Is that still incorrect?

[Babcock_Hall]

It is not a significant contributor to the overall structure.  I suggest thinking about AWK's response.

[NDW]

With the + on the oxygen, your charges are balanced. Given the question, it looks like you are too early in your chemistry study to know that a + on an oxygen and a - on a carbon would be very unstable. It's a good question. When drawing resonance structures, avoid creating point charges and breaking electronegativity rules.

Your revised answer follows the rules, but to a more experience chemist it's a bizzare or "wrong" structure.

http://www.chem.ucalgary.ca/courses/350/Carey5th/Ch01/ch1-7.html