Where two or more resonance structures can represent a molecule, the VSEPR model is not applicable to any such structure.
A multiple bond is treated as if it is a single electron pair and the two or three electron pairs of a multiple bond are treated as a single super pair.
The shape of a molecule depends upon the number of valence shell electron pairs around the central atom.
Pairs of electrons in the valence shell repel one another since their electron clouds are negatively charged.
The valence shell is taken as a sphere with the electron pairs localising on the spherical surface at maximum distance from one another.
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The Correct Option isA
Solution and Explanation
VSEPR theory is based on electron pair repulsion in the valence shell.
Its postulates include:
electron pairs repel each other,
molecular shape depends on the number of bond pairs and lone pairs,
electron pairs arrange themselves to remain as far apart as possible,
multiple bonds are treated as one electron domain with stronger repulsion.
Statement (A) says that VSEPR model is not applicable where resonance structures exist. This is not a standard postulate of VSEPR theory.
Therefore, statement (A) is not a postulate.
Hence, the correct answer is:
\[
\boxed{(A)}
\]