Chemical Bonding and Lewis Structures

Vocabulary flashcards covering chemical bond types, electronegativity differences, Lewis structure rules, formal charges, and resonance structures.

Covalent Bond

A chemical bond in which two or more electrons are shared by two atoms.

Polar Covalent Bond

A covalent bond with greater electron density around one of the two atoms, resulting in electron-rich ($\delta^-$) and electron-poor ($\delta^+$) regions.

Ionic Bond

The electrostatic force that holds ions together in an ionic compound, formed by the transfer of valence electrons.

Non-polar Covalent Bond

A bond type formed when the absolute electronegativity difference between two bonded atoms is less than or equal to $0.4$.

Electronegativity Difference

The absolute value difference in electronegativity between two bonded atoms used to determine bond type: non-polar covalent ($\le 0.4$), polar covalent ($> 0.4$ to $< 2$), or ionic ($\ge 2$).

Single Covalent Bond

A chemical bond formed when two atoms share one pair of electrons.

Double Bond

A chemical bond formed when two atoms share two pairs of electrons.

Triple Bond

A chemical bond formed when two atoms share three pairs of electrons.

Lone Pairs

Unshared pairs of valence electrons present on an atom in a molecule.

Available Electrons ($A$)

The total number of valence electrons in a molecule or ion, calculated by summing valence electrons and adding $1$ for each negative charge or subtracting $1$ for each positive charge.

Needed Electrons ($N$)

The total number of valence electrons required for all atoms to achieve full outer shells, calculated as N = 2(\text{# of H atoms}) + 8(\text{# of other atoms}).

Shared Electrons ($S$)

The total number of electrons shared in bonds within a Lewis structure, calculated as $S = N - A$.

Formal Charge

The difference between the number of valence electrons in a free isolated atom and the number of electrons assigned to that atom in a Lewis structure, calculated as $\text{Formal Charge} = \text{valence electrons} - \text{nonbonding electrons} - \text{number of bonds}$.

Resonance Structure

One of two or more Lewis structures for a single molecule that cannot be represented accurately by only one Lewis structure.

Skeletal Structure

An initial arrangement of atoms showing bonded pairs, constructed by placing the least electronegative element in the center, hydrogen on the outer ends needing $1$ bond, and halogens usually needing $1$ bond.