Hi, I am working on a problem and I am confused as to why my answer is not correct. I've posted a picture of the problem below, it is asking to determine which ions are aromatic.
I know i is not aromatic, because it only has 4 pi electrons, four is not a Huckel number. This is the same for iii.
ii has 6 pi electrons, which is a Huckel number (4n + 2; n = 1). But when I draw the polygon-and-circle test, it seems that four of its electrons lie in nonbonding orbitals. This means it is not aromatic.
iv has 6 pi electrons, which is a Huckel number and it passes the polygon-and-circle test. (I didn't draw that because it would be a pain on paint).
So I determined that only iv. is aromatic, but that's not an option!!
I am thinking the answer would be ii and iv because I know i and iii definitely aren't right, but I don't know why ii would be either.
Any suggestions?
Thanks!