> See also: > - Reference # Resonance Structures While visual representations of molecules are great at showing how *atoms are connected to each other*, they don't accurately represent the *position of the electrons* within the molecule. In reality, electrons can be best described as **clouds of electron density** rather than individual particles, meaning that they can often spread themselves across large regions of a molecule. The concept of **resonance structures** solves this issue by associating multiple potential [[Molecular Structure|structures]] and electron placements > [!warning] > Resonance structures are **imaginary**; the true structure of a molecule is going to be a **hybrid** of its resonance structures. ## Localized vs Delocalized Electrons **Localized electrons:** **Delocalized electrons:** > [!info]- Representations of Resonance Structures > ![[Resonance Structures Representation.png|300]] > > - The potential resonance structures for a molecule are separated by a straight, two-headed arrow. > - This arrow indicates that the representations within the brackets are resonance structures of **a single molecule**. > > --- > **Curved Arrows** > > [!caution] The Two Commandments > **1. Thou shall not break a single bond** > - By definition, resonance structures must have all the same atoms connected in the same order (with several extremely rare exceptions). > > **2. Thou shall not exceed an octet for second-row elements** > - [[Allylic and Vinylic Positions]] ### Pattern Recognition There are five common patterns that can be used to draw a molecule's resonance structures: 1. Allylic lone pair 2. Allylic carbo-cation 3. Lone pair adjacent to carbo-cation 4. $\pi$ bond between two atoms of differing [[electronegativity]] 5. Conjugated $\pi$ bonds enclosed in a ring ![[Pasted image 20220829094913.png]] ### Structure Significance Factors affecting significance: - Electronegativity of atom bearing negative charge - more atoms with full valence electrons -> more significance