Electronic Structure and Bonding


Aufbau principle

principle that states that electrons fill orbitals in order of increasing energy

bond strength

measure of the strength of the bond between two atoms

constitutional isomer

one of two or more molecules that have the same molecular formula but different structural arrangements of atoms and bonds

covalent bond

chemical bond that forms when valence electrons are shared between atoms

dipole moment

vector quantity that defines the extent of the charge on either side of a polar covalent bond, with the direction that points from the positive side of the bond toward the negative side

dipole-dipole interaction

attractive or repulsive force between two polar molecules resulting from partial positive and partial negative charges of the molecules


tendency of an atom to attract electrons toward itself when forming bonds

formal charge

hypothetical charge assigned to an atom in a molecule with the assumption that bonding electrons are shared equally

Hund's rule

rule that states that when filling degenerate orbitals (for example, the 3p orbital), electrons must first singly occupy all the empty orbitals in the subshell before pairing within the same orbital

hybrid orbital

electron orbital that forms when two atomic orbitals combine to form a covalent bond

hydrogen bond

weak intermolecular bond between a hydrogen atom of one molecule and a highly electronegative atom (usually fluorine, oxygen, or nitrogen) of a nearby molecule

intermolecular force

attractive or repulsive force between a molecule and a nearby molecule, atom, or ion

Lewis structure

model that represents covalent bonds and nonbonding electrons with symbols, dots, and lines

London dispersion force

interaction between induced, instantaneous dipoles in nonpolar molecules or atoms

lone pair

valence electron pair that does not form a bond

molecular geometry

shape formed by the central atom, considering only bonding electron pairs

molecular orbital

mathematical function that gives the probability of locating an electron in a localized volume of space

molecular orbital theory

theory that atomic electron orbitals in covalent bonds are replaced by electron orbitals that belong to the entire molecule

nonpolar covalent bond

covalent bond in which the nuclei of the bonded atoms exert equal or nearly equal force on the shared electrons

octet rule

rule that states that atoms tend to share or donate electrons such that the valence shell contains eight electrons: Octet=ns+np=8\text{Octet}=ns + np=8


region in which an electron has a high probability of being located. Orbitals are described by the quantum numbers s, p, d, and f, which differ from one another by their shapes.

Pauli's exclusion principle

states that paired electrons may never have the same spin value, which means they may not have the same four quantum numbers

polar covalent bond

covalent bond in which the electron density is more localized on one end of the bond. One end is slightly positive, and one end is slightly negative.

quantum mechanics

branch of science that deals with subatomic particles, their behaviors, and their interactions

valence bond theory

theory that states that the electrons in a covalent bond remain centralized around their original nuclei and that their atomic orbitals overlap

valence electron

electron in the outermost shell of an atom

valence shell electron pair repulsion (VSEPR) theory

covalent bond theory that uses the repulsive forces between single electrons and pairs of electrons about the central atom to predict their relative positions around the atomic nuclei

van der Waals forces

dipole-dipole interaction, London dispersion force, hydrogen bonding, and the intermolecular force between permanent molecular dipoles