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Problem: Determine whether a molecule with a flat, continuous ring containing 5 carbon atoms and 1 negative charge (Cyclopentadienyl anion, C5H5(-)) is aromatic according to Huckel's rule. Step 1: Check if the molecule is cyclic and planar. The problem states it is a flat ring, so it satisfies the geometry requirement. Step 2: Count the total number of pi-electrons participating in the ring cloud. Each of the double bonds contributes 2 pi-electrons (there are 2 double bonds, giving 4 electrons), and the negative charge represents a lone pair of electrons residing in a p-orbital that joins the ring system (contributing 2 electrons). Total pi-electrons = 4 + 2 = 6. Step 3: Apply Huckel's rule formula, which is total pi-electrons = 4n + 2. Set 4n + 2 equal to 6. Step 4: Solve for n. 4n = 6 - 2, so 4n = 4, which means n = 1. Step 5: Check if n is a whole integer. Since n = 1 is a whole number, the cyclopentadienyl anion obeys Huckel's rule and is aromatic.