The integer “n” in Hückel’s rule for naphthalene is 2.
Naphthalene, with 10 π electrons, satisfies the 4n+2 rule where 4(2)+2=10, confirming its aromaticity.​

Naphthalene follows Hückel’s rule of aromaticity as a polycyclic aromatic hydrocarbon with two fused benzene rings. Its structure features 10 delocalized π electrons across a planar, fully conjugated system of sp²-hybridized carbons.​

Hückel’s Rule Basics

Hückel’s rule states that a cyclic, planar, fully conjugated molecule is aromatic if it has 4n+2 π electrons, where n is a non-negative integer (0, 1, 2, etc.). Common values include 2 (n=0), 6 (n=1), 10 (n=2), and 14 (n=3) π electrons. This electron count ensures all bonding molecular orbitals are filled, enhancing stability through delocalization.​

Naphthalene Structure and π Electrons

Naphthalene (C₁₀H₈) consists of two fused six-membered rings sharing two carbons, forming a fully conjugated system. Each ring resembles benzene but shares electrons; the total π electrons come from five double bonds equivalent, yielding 10 π electrons (2 per bond). All 10 carbons are sp² hybridized, enabling p-orbital overlap for delocalization.​

Calculating n for Naphthalene

Set 4n + 2 = 10:
4n=8
n=2
Since n=2 is an integer, naphthalene is aromatic. This matches benzene (n=1, 6 π electrons).​

Why No Options? Common Misconceptions

The query mentions “every option,” but none are provided; typical exam distractors include n=0 (2 electrons, too few), n=1 (6 electrons, one ring only), or n=3 (14 electrons, anthracene). Some err by counting 12 electrons (ignoring fusion), but correct total is 10. Naphthalene’s peripheral 10-electron circuit confirms aromaticity.​

Significance for CSIR NET

This concept tests aromaticity criteria: planarity, conjugation, and 4n+2 electrons. Naphthalene’s stability reflects real-world applications in mothballs and dyes. Master via practice: anthracene (14 π, n=3) is aromatic too.​