Lewis Structures & Chemical Bonding – Key Vocabulary

These flashcards summarize the essential vocabulary terms introduced in the lecture on drawing Lewis structures, understanding bonding, and evaluating resonance and formal charge.

Valence Electrons

The electrons located in the outermost shell of an atom that participate in chemical bonding.

Lewis Symbol

A diagram showing an element’s symbol surrounded by dots that represent only its valence electrons.

Lewis Structure (Skeleton)

The initial drawing of a molecule that connects all atoms with single bonds to establish the framework for electron counting.

Octet Rule

The tendency of main-group atoms to gain, lose, or share electrons until they possess eight valence electrons, like a noble gas.

Ionic Bond

An electrostatic attraction between oppositely charged ions formed by complete electron transfer—no line is drawn between ions in a Lewis diagram.

Covalent Bond

A bond formed when two non-metals share pairs of electrons; represented by lines in Lewis structures.

Single Bond

A covalent bond consisting of one shared electron pair (one line) worth 2 electrons.

Double Bond

A covalent bond made of two shared electron pairs (two lines) worth 4 electrons.

Triple Bond

A covalent bond of three shared electron pairs (three lines) worth 6 electrons; shortest and strongest among single, double, and triple bonds.

Lone Pair (Unshared Pair)

A pair of valence electrons not involved in bonding and belonging to a single atom; also called a ‘loan’ pair because it can be donated.

Electronegativity

A measure of an atom’s ability to attract bonding electrons; increases left-to-right across a period and decreases down a group.

Least Electronegativity Rule

When drawing a skeleton, place the least electronegative atom (except H) in the center of the molecule.

Bond Length

The distance between two bonded nuclei; single bonds are longest, triple bonds shortest.

Bond Strength

The energy required to break a bond; single bonds are weakest, triple bonds strongest.

Electron Deficiency

A situation where the electrons available are fewer than those required to complete octets, forcing the formation of multiple bonds.

Formal Charge

A book-keeping charge assigned by assuming equal electron sharing: FC = (valence e⁻) – (dots) – (lines/2).

Resonance Structure

One of two or more Lewis structures with the same skeleton and electron count but different electron placement; depicted with a double-headed arrow.

Isomer

Compounds with the same molecular formula but different atomic arrangements (different skeletons), giving distinct properties.

Best Resonance Contributor

The resonance form with the most zeros in formal charges and any negative charge on the more electronegative atom.

Bonding Pair

A pair of electrons shared between two atoms, depicted as a line in Lewis structures.

Family Fund Analogy

Lecture metaphor: once electrons are shared (put into the ‘family fund’), all atoms own them equally, regardless of their original contribution.

Cation

A positively charged ion formed when an atom loses one or more electrons (e.g., Na⁺).

Anion

A negatively charged ion formed when an atom gains one or more electrons (e.g., Cl⁻).

Each Line = 2 Electrons Rule

When counting electrons in Lewis structures, every drawn bond line must be counted as exactly two electrons.