Chapter 4: Chemical Bonding and Molecular Geometry

Vocabulary practice flashcards covering chemical bonds, ionic and molecular compounds, nomenclature, Lewis structures, formal charge, resonance, and VSEPR molecular geometry.

Ionic Bond

The electrostatic attraction between charged particles resulting from the complete transfer of one or more electrons from one atom to another; typically formed between a metal and a nonmetal.

Covalent Bond

A chemical bond resulting from the sharing of several (usually two) electrons between two atoms.

Metallic Bond

A type of chemical bonding in which metal atoms are bonded to several other atoms and electrons are delocalized.

Cation

A positively charged particle formed when an atom, typically a metal, loses one or more electrons.

Anion

A negatively charged particle formed when an atom, typically a nonmetal, gains one or more electrons.

Monatomic Ion

An ion formed from only a single atom.

Polyatomic Ion

An electrically charged molecule consisting of a group of bonded atoms with an overall net charge.

Oxyanion

A polyatomic ion that contains one or more oxygen atoms.

Acid Nomenclature System

The systematic naming scheme where an anion ending in -ide converts to hydro- -ic acid, an anion ending in -ate converts to -ic acid, and an anion ending in -ite converts to -ous acid.

Oxyacid

A compound containing hydrogen, oxygen, and at least one other element that imparts acidic properties, typically consisting of hydrogen combined with an oxygen-containing polyatomic ion.

Hydrate

A compound, often ionic, that contains one or more water molecules bound within its crystal structure.

Anhydrous Compound

The dry compound that remains after the bound water molecules of a hydrate have been removed, typically by heating.

Bond Length

The optimal internuclear distance between two bonded atoms (such as $74\,\text{pm}$ in $\text{H}_2$) at which potential energy is at a minimum and attractive and repulsive forces are balanced.

Bond Polarity

A measure of how equally or unequally electrons in a covalent bond are shared between two atoms.

Nonpolar Covalent Bond

A covalent bond in which bonding electrons are shared equally between atoms, resulting in an electronically symmetrical electron distribution.

Polar Covalent Bond

A covalent bond with an unsymmetrical electron distribution in which bonding electrons are attracted more strongly by one atom than the other, resulting in partial charges ($\delta+$ and $\delta-$).

Electronegativity

The ability of an atom in a molecule to attract shared electrons in a covalent bond toward itself.

Dipole Moment ($\mu$)

A quantitative measure of the polarity of a bond or molecule calculated as $\mu = Qr$, where two equal but opposite charges ($Q$) are separated by a distance ($r$), measured in debyes (D).

Lewis Structure (Electron-Dot Structure)

A diagrammatic representation of an atom's valence electrons using dots that indicates how valence electrons are distributed among bonding pairs and lone pairs in a molecule.

Lone Pair

An unshared pair of valence electrons located on only one atom in a Lewis structure.

Bonding Pair

A pair of electrons shared between two atoms in a Lewis structure, represented by two dots or a single line.

Single Bond

A covalent bond in which two atoms share one pair of electrons.

Double Bond

A covalent bond formed by sharing two pairs of electrons between two atoms; it is shorter and stronger than a single bond.

Triple Bond

A covalent bond formed by sharing three pairs of electrons between two atoms; it is shorter and stronger than corresponding single and double bonds.

Expanded Octet

An exception to the octet rule occurring in period 3 and heavier elements, where the central atom accommodates more than eight valence electrons by utilizing available $d$-orbitals.

Formal Charge

The hypothetical charge calculated for an individual atom in a Lewis structure using the formula: $\text{Formal Charge} = (\text{valence } e^- \text{ in free atom}) - (\text{nonbonding } e^-) - \frac{1}{2}(\text{bonding } e^-)$.

Resonance Structures

Two or more equivalent or valid Lewis structures for the same molecule or polyatomic ion that differ only in the arrangement of electrons, not the placement of atoms.

VSEPR Model

The Valence-Shell Electron-Pair Repulsion model; a framework predicting molecular geometry based on the principle that electron pairs (charge clouds) repel each other and stay as far apart as possible.

Electron Domain

A region of electron density around a central atom pointing in a particular direction, counted as a single, double, or triple bond or a lone pair.

Electron-Domain Geometry

The three-dimensional arrangement of all electron domains (both bonding pairs and nonbonding lone pairs) around a central atom.

Molecular Geometry

The three-dimensional arrangement in space of only the bonded atoms in a molecule, determined relative to the positions of the atomic nuclei.

Axial Position

The two positions situated along the vertical axis perpendicular to the equatorial plane ($90^\circ$ to the equatorial bonds) in a trigonal bipyramidal geometry.

Equatorial Position

The three positions forming an equilateral triangle in the horizontal plane ($120^\circ$ relative to one another) in a trigonal bipyramidal geometry, which are preferentially occupied by lone pairs.