Chapter 1-7 Notes: Lewis Structures and Formal Charge (Vocabulary)

Vocabulary flashcards covering octet rules, formal charge, electron counting, bond-line formulas, lone pairs, and isomer concepts from the lecture notes.

Octet rule

Most main‑group elements try to have eight electrons around each atom (Hydrogen typically 2). It guides how many bonds and lone pairs an atom can have.

Unpaired electrons

Electrons not paired in the same orbital; can be used to form additional bonds to satisfy octets (radical behavior).

Cyclic structure

A molecule or ion where the atoms form a ring; can help satisfy octets and create different connectivity.

Acyclic structure

Open-chain structure with no rings; not containing a cycle.

Constitutional isomers

Isomers with the same molecular formula but different connectivity of atoms.

Electron counting

Process of tallying total valence electrons for all atoms and distributing them as bonds and lone pairs while respecting the octet rule.

Formal charge

Hypothetical charge on an atom: FC = valence electrons − (bonds + nonbonding electrons). Used to identify electron distribution.

Anion

Species with a negative formal charge (gained an electron).

Cation

Species with a positive formal charge (lost an electron).

Nonhydrogen atoms

Atoms other than hydrogen; central to building Lewis structures and performing electron accounting.

Lone pairs

Pairs of electrons localized on an atom that are not involved in bonding.

Bond line formula (skeletal formula)

A simplified representation using lines for bonds; carbon atoms are implied at line ends/vertices; hydrogens on carbons are often implicit.

Hydrogens in bond-line drawings

Hydrogens bound to noncarbon atoms are shown; hydrogens bound to carbons are usually implied by octet needs.

Lewis structure

A diagram showing all bonds, lone pairs, and any formal charges for a molecule.

Valence

Number of bonds an atom typically forms (C=4, O=6, N=5, etc.) and its usual valence electrons.

Electron counting with charge

If a species has a negative charge, add an electron; if it has a positive charge, subtract an electron from the total.

Charge distribution trends

Common patterns: carbon with four bonds and no lone pairs tends to be neutral; oxygen with one bond and three lone pairs tends to bear −1; nitrogen with four bonds tends to bear +1.

Bond-line vs Lewis structure

Bond-line (skeletal) draws only bonds and atom connections; Lewis structure shows all atoms with all lone pairs and formal charges.

Connectivity and constitutional isomers

Changing how atoms are connected (connectivity) to generate different constitutional isomers from the same formula.