Question

Which of the following is not the correct condition for resonance?
A. The positions of all the atomic nuclei in the resonating structures are not the same.
B. The resonating structures must have the same number of unpaired or paired electrons.
C. The molecules exhibiting resonance must be planar in nature.
D. The resonating structures must have nearly the same energies.

Answer 1

Hint: The representation of the structure of a molecule as a weighted average of two or more hypothetical structures, that only differs by the arrangement of electrons but has same positions for atoms is referred to as resonance. Many properties of molecules can be explained using resonance.

Complete step by step answer:
Sometimes, it is not possible to represent the molecule with only one structure. For this more than one structure has to be proposed. But a single structure does not exhibit all the observed properties of the molecule. This is usually referred to as resonance or mesomerism or delocalization.
Resonance structures are a group of two or more Lewis structures that represent a single polyatomic species but here, the electrons are distributed around the structure differently. When electrons may pass through opposing pi structures, resonance takes place. Resonance is a method to describe the combination of several contributing structures into a hybrid structure.
Resonance can also be defined as the representation of structure of a molecule as a weighted average of two or more hypothetical structures, which only differ by the arrangement of electrons.
Some features of resonance are,
A. The structures with different arrangements of electrons in the same position for atoms are called resonance structures or canonical forms or contributing structures.
B .The resonance structures are imaginary structures and the actual structure of the molecule is the hybrid of all the contributing resonance structures.
C. The energy of a resonance hybrid is always less than the energy of all contributing resonance structures.
D. In resonance, the delocalization of electrons is shown using curved arrows.
E. The resonating structures should be planar in structure.
F. The different resonating structures should have the same or nearly the same energies.

So, the correct answer is Option A.

Note: In resonance, the contributing structures are always shown to be linked by using double headed arrows $$\rightleftarrows$$. As the number of contributing structures increases, stability also increases.
The difference between the energy of resonance hybrid and the most stable resonance structure of a molecule is known as the resonance stabilization energy of that molecule