Chemical Bonding, Lewis Structures, and Molecular Geometry Vocabulary

Vocabulary flashcards covering Chapter 4 (Chemical Bonding and Lewis Structures) and Chapter 5 (Molecular Geometry and Advanced Theory of Bonding) based on Dr. Yifen Li's chemistry lectures.

Cation

A positively charged ion formed when a metal atom loses one or more valence electrons.

Anion

A negatively charged ion formed when a nonmetal atom gains one or more valence electrons.

Ionic Bonding

The electrostatic attraction that holds oppositely charged ions together in an ionic compound, formed when valence electrons are transferred from a metal atom to a nonmetal atom.

Covalent Bond

A chemical bond formed when two atoms with similar tendencies to attract electrons share electrons between each other.

Pure Covalent Bond

A covalent bond formed between identical atoms (such as $\text{H}_2$ and $\text{Cl}_2$) in which the bonding electrons are shared equally.

Polar Covalent Bond

A covalent bond formed between different atoms where bonding electrons are shared unequally, giving the more electronegative atom a partial negative charge ($\delta-$) and the less electronegative atom a partial positive charge ($\delta+$).

Electronegativity (EN)

A measure of the tendency of an atom in a molecule to attract electrons or electron density towards itself.

Monatomic Ion

An ion formed from only one single atom.

Polyatomic Ion

An ion composed of two or more atoms covalently bonded together that functions as a single charged unit.

Binary Molecular Compound

A compound composed of two different nonmetal elements that share valence electrons.

Binary Acid

An acid consisting of hydrogen and one nonmetallic element, named with the prefix hydro- and the suffix -ic acid (e.g., $\text{HCl}(aq)$, hydrochloric acid).

Oxyacid

An acid containing hydrogen, oxygen, and another central element, named based on its polyatomic anion where -ate becomes -ic acid and -ite becomes -ous acid.

Lewis Dot Symbol

A notation consisting of an element's chemical symbol surrounded by dots, where each dot represents a valence electron.

Valence Electrons

The outermost electrons of an atom having the greatest principal quantum number $n$, which determine an element's chemical bonding behavior.

Lewis Structure

A structural representation of covalent bonding in which shared electron pairs are shown as dashes and unshared valence electrons are shown as pairs of dots on individual atoms.

Lone Pairs

Pairs of valence electrons that are not involved in covalent bonding (also referred to as non-bonding electrons).

Double Bond

A covalent bond formed when two pairs of electrons (four electrons total) are shared between a pair of atoms.

Triple Bond

A covalent bond formed when three pairs of electrons (six electrons total) are shared between a pair of atoms.

Octet Rule

The tendency of main group atoms to form enough bonds to obtain eight valence electrons in their outer shell.

Resonance Structure

One of two or more equally valid Lewis structures for a single species that cannot be accurately represented by a single Lewis structure, differing only in the positions of electrons.

Free Radical

An odd-electron molecule or atom that contains an unpaired valence electron (such as $\text{NO}_2$).

Hypervalent Molecule

A molecule containing a central atom from the third period or higher ($n \ge 3$) that shares more than four pairs of valence electrons due to available empty d orbitals.

Formal Charge

The hypothetical charge assigned to an atom in a molecule, calculated as \text{formal charge} = \text{# valence } e^- - \text{# lone pair } e^- - \frac{1}{2}\text{# bonding } e^-.

VSEPR Theory

Valence shell electron-pair repulsion theory; a model that predicts 3D molecular structure by assuming electron pairs in the valence shell adopt an arrangement minimizing repulsions among regions of high electron density.

Electron-Pair Geometry

The spatial arrangement of regions of high electron density (including single, double, triple bonds and lone pairs) around a central atom.

Molecular Structure

The three-dimensional arrangement that describes only the placement of the bonded atoms in a molecule (also known as molecular geometry).

Wedge and Dash Notation

A 3D drawing convention where solid lines represent bonds in the plane of the page, solid wedges represent bonds coming up out of the plane, and dashed lines represent bonds going down into the plane.

Axial Position

In a trigonal bipyramidal electron-pair geometry, the positions perpendicular to the trigonal plane surrounded by neighboring bonds at $90^\circ$ angles.

Equatorial Position

In a trigonal bipyramidal electron-pair geometry, the three positions arranged within the trigonal plane at $120^\circ$ angles, which provide more spacious room for accommodating larger lone pairs.

Molecular Polarity

A physical property determined by molecular structure and bond polarities, making a molecule polar when it has polar bonds and lacks molecular symmetry.

Valence Bond Theory

A theory describing a covalent bond as the overlap of half-filled atomic orbitals (each containing a single electron) yielding two shared electrons of opposite spin.

Hybridization

The process of mixing two or more atomic orbitals on a central atom to form a new set of equivalent hybrid orbitals.

Hybrid Orbitals

A set of orbitals generated by combining atomic orbitals, where all orbitals in the set are equivalent in shape and energy, and equal in number to the atomic orbitals combined.

Sigma ($\sigma$) Bond

A covalent bond formed by the end-to-end overlap of atomic or hybrid orbitals, with electron density concentrated along the internuclear axis.

Pi ($\pi$) Bond

A covalent bond resulting from the side-by-side overlap of two p orbitals, where regions of overlap lie on opposite sides of the internuclear axis.

Node

A plane along the internuclear axis in a pi bond where there is zero probability of finding an electron.

Trigonal Planar Electron-Pair Geometry

The spatial arrangement formed when a central atom has three regions of high electron density, placing them at $120^\circ$ angles in a single plane.

Tetrahedral Electron-Pair Geometry

The spatial arrangement formed when a central atom has four regions of high electron density, resulting in ideal bond angles of $109.5^\circ$.

Trigonal Bipyramidal Electron-Pair Geometry

The spatial arrangement formed when a central atom has five regions of high electron density, featuring axial positions at $90^\circ$ and equatorial positions at $120^\circ$.

Octahedral Electron-Pair Geometry

The spatial arrangement formed when a central atom has six regions of high electron density, placing all positions at $90^\circ$ relative to adjacent bonds.

Trigonal Pyramidal Molecular Geometry

The molecular structure resulting from a central atom with four electron regions consisting of three bonding pairs and one lone pair (e.g., $\text{NH}_3$).

Bent Molecular Geometry

A non-linear molecular structure resulting from a central atom with either three electron regions (two bonding pairs, one lone pair) or four electron regions (two bonding pairs, two lone pairs, such as $\text{H}_2\text{O}$).

Seesaw Molecular Geometry

The molecular structure resulting from a central atom with five electron regions consisting of four bonding pairs and one equatorial lone pair (e.g., $\text{SF}_4$).

T-Shaped Molecular Geometry

The molecular structure resulting from a central atom with five electron regions consisting of three bonding pairs and two equatorial lone pairs (e.g., $\text{ClF}_3$).

Square Pyramidal Molecular Geometry

The molecular structure resulting from a central atom with six electron regions consisting of five bonding pairs and one lone pair (e.g., $\text{BrF}_5$).

Square Planar Molecular Geometry

The molecular structure resulting from a central atom with six electron regions consisting of four bonding pairs and two lone pairs positioned on opposite sides (e.g., $\text{XeF}_4$).

Naming Monatomic Metal Cations

Named using the element's full name, followed by a Roman numeral in parentheses if the metal forms cations with variable charges (e.g., $\text{Fe}^{2+}$ is iron(II) ion).

Naming Monatomic Nonmetal Anions

Named by taking the stem of the element's name and adding the suffix -ide (e.g., $\text{Cl}^-$ is chloride).

Rules for Naming Binary Molecular Compounds

Name the first element fully, name the second element with an -ide suffix, and use Greek prefixes to indicate atom counts (omitting mono- on the first element).

Rules for Naming Ionic Compounds

Name the cation first (including Roman numerals if variable in charge) followed by the anion; Greek prefixes are never used.

Rules for Naming Binary Acids

Acids consisting of hydrogen and one nonmetal; named with the prefix hydro-, the stem of the nonmetal, and the suffix -ic acid (e.g., $\text{HCl}(aq)$ is hydrochloric acid).

Rules for Naming Oxyacids

Acids containing hydrogen, oxygen, and a central element; named based on the polyatomic anion where -ate becomes -ic acid and -ite becomes -ous acid.