[Brook]

If I have a molecule like the one shown, is it antiaromatic because it does not satisfy Huckle's Rule; it only has 4 pi electrons?

[Brook]

My apologies for the extremely large picture.

[limonade]

It is actually going to be aromatic because the oxygen is sp2 hybridized. One of the lone pairs on oxygen is in a p orbital. So the number of pi electrons is actually 6. The molecule is planar , and has continous circle of p orbitals. So all conditions satisfied, it will be aromatic.

[PhDoc]

Yep, aromatic. I typically test student for both aromaticity and resonance at the same time via questions just like this. I would suggest getting more of these examples. If not available, ask your professor to assign "extra problems for the class."