Aromaticity requires that there be alternating pi bonds (double bonds) and that there be 4n + 2 pi electrons (two for each double bond) where n is a
positive integer. This ends up giving a pattern of: 2, 6, 10, 14, 18, ... So, for example, benzene is aromatic because it has 6 pi
electrons/orbitals (4*1 + 2 = 6). Cyclobutadiene is anti-aromatic because 4n + 2 can never equal 4. See "Huckel's Rule".
Just look for alternating double bonds in a ring first, then check it against that rule to determine if it's aromatic or not.
Of course, it gets a bit more complicated when you get into larger ring systems but I think this explanation is just fine for now.
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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