Here the starred set contains the highest number of atoms.
[1] When this condition is met, the secular determinant in the Hückel approximation has a simpler form, since cross-diagonal elements between atoms in the same set are necessarily 0.
Alternant hydrocarbons display three very interesting properties:[2] Moreover, if the alternant hydrocarbon contains an odd number of atoms then there must be an unpaired orbital with zero bonding energy (a non-bonding orbital).
Simple algebra allows the assignment of all coefficients and then normalize them.
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