Oxidation of pentalene with two equivalents of $Sb F_{5}$ removes two π electrons and gives the pentalene dication. Classify the dication as aromatic, anti-aromatic or non-aromatic. (assume the ring is planar)

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The dication has 3 C = C bonds (6 π electrons) and both positively charged carbons contribute empty p orbitals : 6 π electrons (4n+2, n = 1) in a planar, fully conjugated periphery. The neutral pentalene has 8π (anti-aromatic), so oxidation converts it into an aromatic species.

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