Final answer:
In chemistry, the concept of resonance involves labeling structures as major, minor, or insignificant based on formal charge placement, p-orbital size and orientation, and electronegativity. Major contributors have resonance stabilization with properly placed formal charges and properly sized p-orbitals, while minor contributors may have unfavorable charge distribution or mismatched p-orbital sizes.
Step-by-step explanation:
The question pertains to the concept of resonance in chemistry, particularly the assessment of resonance contributors as major, minor, or insignificant. Labels are assigned to resonance structures based on several considerations, including the placement of formal charges, the size and orientation of p-orbitals, and the electronegativity of the atoms involved.
For major contributors, resonance stabilization is highest when there are equal contributors without formal charges, and when any formal charges present are on atoms where they are most stabilized (negative on electronegative atoms and positive on less electronegative atoms).
Minor contributors will typically involve formal charges that are less stabilized, such as a positive charge on an electronegative atom or a negative charge on an atom that is less electronegative. Furthermore, mismatching p-orbital sizes between atoms participating in resonance can also lead to a structure being labeled as minor or even insignificant, as effective overlap is reduced.
When drawing resonance structures, one must only move pi electrons or lone pairs and not the sigma electrons. This will allow the generation of various contributing structures that represent the delocalization of electrons within a molecule. The formal charge on each atom should be calculated for all possible resonance structures to understand their contribution to the overall resonance hybrid.