Formal Charges and Resonance Lecture Review

Flashcards covering the concepts of formal charge calculation, Lewis structure optimization, and resonance as discussed in the lecture transcript.

Formal Charge

The hypothetical charge of an atom in a molecule if the electrons in the bonds were redistributed evenly between the atoms.

Formal Charge Formula

Taking the number of valence shell electrons of a free atom, subtracting the number of lone pair electrons, and subtracting half the number of bonding electrons: $\text{Valence} - \text{Lone Pairs} - \frac{1}{2}(\text{Bonding})$.

Neutral Molecule Rule

The sum of the formal charges should all equal $0$ in a neutral molecule.

Polyatomic Ion Rule

The sum of the formal charges in an ion should equal the charge of the ion.

Molecular Structure

The arrangement of atoms in a molecule or an ion.

Preferred Formal Charge

A guideline stating that it is preferable for all atoms to have a formal charge of $0$, or as close to $0$ as possible.

Electronegative Atom Rule

It is preferable for more electronegative atoms to have any negative formal charge.

Adjacent Atom Rule

It is preferable for adjacent atoms to have formal charges of $0$ or of the opposite sign.

$ICL_4^-$ Valence Total

The total number of valence electrons including iodine ($7$), four chlorines ($28$), and the $-1$ charge, totaling $36$ electrons.

Lewis Structure Ion Notation

The practice of surrounding a charged ion with brackets and putting the charge on the outside.

Carbon Dioxide ($CO_2$) Most Likely Structure

The structure on the left with carbon in the center and double bonds on either side, where all atoms have a formal charge of $0$.

Least Electronegative Element

The atom typically placed in the center of a Lewis structure, such as iodine in $ICL_4^-$ or sulfur in $SCl_2O$.

$N_2O$ (Dinitrogen Monoxide)

Commonly known as laughing gas, this molecule is used as an anesthetic in minor surgeries like wisdom tooth extraction.

Resonance

A situation in which one Lewis structure is insufficient in describing the bonding in a molecule and the structure is the average of multiple forms.

Resonance Form

One of two or more Lewis structures that have the same arrangement of atoms but a different arrangement of electrons.

Resonance Hybrid

The average of the resonance forms shown by individual Lewis structures which represents the actual electronic structure.

Double-sided arrow

The symbol ($\leftrightarrow$) used between resonance structures to indicate that the actual structure is an average of the forms.

${NO}_2^-$ (Nitrite Ion)

An ion that shows resonance through two equivalent structures where the placement of the double and single bonds is swapped.

${CO}_3^{2-}$ (Carbonate Ion)

An ion where the double bond location could be on any of the three oxygens, making all bonds identical in the resonance hybrid.

Valence electrons in $SCl_2O$

A molecule consisting of sulfur ($6$), two chlorines ($14$), and oxygen ($6$), totaling $26$ valence electrons.