What is aromaticity? Explain with suitable examples. State the Huckel rule and explain it with a suitable example. Write the requirements for aromatic character in a compound. Show aromatic structures having $1$,$2$,and $3$ rings with suitable examples.

(N/A) Aromaticity is a property of cyclic,planar,conjugated systems that exhibit extra stability due to the delocalization of $\pi$ electrons.
$(a)$ Requirements for aromatic character in a compound:
$(i)$ The compound must have a cyclic structure.
$(ii)$ The cyclic compound must be planar.
$(iii)$ There must be complete delocalization of $\pi$ electrons in the ring.
$(iv)$ The ring must contain $(4n+2) \pi$ electrons,where $n$ is an integer $(n=0, 1, 2, \dots)$. This is known as the Huckel rule.
$(b)$ Huckel's rule: $A$ planar,cyclic,fully conjugated system is aromatic if it contains $(4n+2) \pi$ electrons.
$(c)$ Examples:
$(i)$ $1$ ring: Benzene $(C_6H_6)$. It is cyclic,planar,and has $6 \pi$ electrons ($n=1$,$4(1)+2=6$).
$(ii)$ $2$ rings: Naphthalene $(C_{10}H_8)$. It is cyclic,planar,and has $10 \pi$ electrons ($n=2$,$4(2)+2=10$).
$(iii)$ $3$ rings: Anthracene $(C_{14}H_{10})$. It is cyclic,planar,and has $14 \pi$ electrons ($n=3$,$4(3)+2=14$).
Cyclopentadienyl anion is also aromatic as it has $6 \pi$ electrons ($4$ from two double bonds and $2$ from the lone pair on the carbon atom).