Localized orbital overlap and resonance are complementary chemical descriptions.
Key knowledge
Valence-bond models describe bonding through atomic-orbital overlap and paired electrons. When one Lewis structure inadequately represents electron distribution, resonance forms provide alternative bookkeeping descriptions of one species; the species does not alternate between those drawings.
Conditions and scope
Orbital overlap and Lewis forms are models, not directly observed electron paths.
Resonance forms retain nuclear connectivity; their contributions need not be equal.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Paul Flowers, Klaus Theopold, Richard Langley and William R. Robinson — OpenStax, Rice University2 sources
Valence-bond models describe bonding through atomic-orbital overlap and paired electrons. When one Lewis structure inadequately represents electron distribution, resonance forms provide alternative bookkeeping descriptions of one species; the species does not alternate between those drawings.
The source compares localized and delocalized orbital descriptions.
Removal of an α proton from a suitable carbonyl compound forms an enolate whose charge is distributed between oxygen and carbon by conjugation. Enol–carbonyl tautomerization changes proton placement and bonding; it is distinct from resonance. Enolate carbon or oxygen can react according to reagent and conditions.
Resonance bookkeeping differs from tautomer interconversion.
An amine's basicity can be described by the acidity of its conjugate ammonium species under specified conditions. Resonance and substituent environment affect nitrogen lone-pair availability; amide nitrogen is generally much less basic than ordinary amine nitrogen because of carbonyl delocalization. Protonation can change solubility and extraction partitioning.
Delocalization changes local electron availability.
An empirical formula gives the simplest whole-number ratio of constituent atoms. A molecular formula gives their counts in a specified molecule; different structures may share it. A structural formula also represents connectivity. For an extended ionic solid, a formula unit expresses a stoichiometric ratio rather than claiming that the crystal consists of discrete molecules.
A structural representation conveys connectivity/electron accounting beyond the composition shown by a molecular formula.
In a Lewis structure, formal charge assigns each atom its nonbonding electrons and half of its bonding electrons, then compares that count with the neutral atom's valence-electron count. Formal charges sum to the species' net charge. They are bookkeeping values, distinct from partial charge and from oxidation state's ionic approximation of heteronuclear bonds.
Formal charges are attached to specified Lewis contributors and do not make resonance contributors separate oscillating species.
For a molecular Lewis diagram, total the atoms' valence electrons, adding electrons for negative charge and subtracting them for positive charge. A bond line represents a shared electron pair; dots can represent lone pairs. Place these electrons on a proposed atom connectivity and check the total charge and electron count. Hydrogen commonly has a duet, and many main-group centers an octet; odd-electron, electron-deficient and hypervalent species require exceptions.
Different valid Lewis contributors can represent one delocalized structure rather than distinct alternating species.