Which statement about FNNF is not correct?

The statement regarding FNNF being more stable than its structural isomer with both fluorine atoms bonded to the same nitrogen is indeed incorrect because it provides inaccurate information about the stability of these molecules.

FNNF (fluoroazene) is a molecule with a linear structure where nitrogen atoms are sequentially bonded to each other, and the presence of a central nitrogen allows for a distribution of electron density that contributes to its stability. In contrast, the structural isomer where both fluorine atoms are bonded to a single nitrogen atom creates significant electron repulsion. This affects the molecule's overall stability.

In addition, FNNF exhibits resonance, which allows for different electron arrangements that further stabilize the molecule. The ability to delocalize electrons across the nitrogen atoms adds to this instability in the isomer where both fluorine atoms are bonded to the same nitrogen. Thus, the assertion that FNNF is more stable than its isomer is not supported when considering the electron arrangements and interactions present in both structures.