Chemical Bonding, Nomenclature, and Molecular Geometry

Vocabulary practice flashcards covering Lewis structures, ionic and covalent compound nomenclature, acid naming conventions, and VSEPR molecular geometry.

Lewis Structure (2D)

A two-dimensional representation of a covalent or molecular compound showing atom arrangement, types of chemical bonds, and valence electrons distributed to satisfy the octet rule.

Octet Rule

The guiding chemical principle stating that bonds form between atoms such that all participating atoms fill their valence shells to eight electrons.

Central Atom Selection Rules

Structural guidelines specifying that hydrogen is never the central atom, carbon is always the central atom, and the central atom is generally the less electronegative element.

Resonance

A condition in which more than one valid Lewis structure can be drawn for a molecule, with the resulting true electron structure treated as the average of all valid resonance structures.

Ionic Bond

The electrostatic attractive force formed between cations and anions when representative metal atoms lose valence electrons and representative nonmetal atoms gain them, giving both noble gas configurations.

Periodic Ion Charges

The predictable charges formed by elements upon electron transfer: Group $1\text{A}$ metals lose $1$ electron to become $+1$, Group $2\text{A}$ become $+2$, Group $3\text{A}$ become $+3$, Group $5\text{A}$ nonmetals gain $3$ electrons to become $-3$, Group $6\text{A}$ become $-2$, and Group $7\text{A}$ become $-1$.

Binary Ionic Compound

A neutral ionic compound composed exclusively of two elements: a metal cation and a nonmetal anion.

Ternary Ionic Compound

An ionic compound containing more than two elements, typically formed between a metal cation and a polyatomic ion.

Characteristics of Ionic Compounds

Distinctive physical properties of ionic substances, including high melting and boiling points, solubility to some extent in water, and good electrical and thermal conductivity.

Criss-Cross Method

A method of writing the formula unit of an ionic compound by crossing over the numerical charges of the respective ions to make the combined compound electrically neutral.

Covalent Bond

A type of chemical bond where atoms satisfy the octet rule by sharing valence electrons, resulting in an attractive force between two atoms attracted to the shared electron pair.

Pure Covalent Bond (Nonpolar Covalent Bond)

A covalent bond formed when electrons are shared equally between two participating atoms, as observed in homonuclear diatomic molecules such as $H_2$, $N_2$, and $O_2$.

Polar Covalent Bond

A covalent bond formed between different atoms where electrons are shared unequally, producing a polarized bond with partial positive ($\delta+$) and partial negative ($\delta-$) charges.

Space-Filling Model of $H_2O$

A molecular representation illustrating water with unequal electron sharing, where the central oxygen atom carries a partial negative charge ($\delta-$) and each hydrogen atom carries a partial positive charge ($\delta+$).

Greek Prefixes (Covalent Nomenclature)

Number prefixes used to specify the count of atoms in binary covalent compounds: mono- ($1$), di- ($2$), tri- ($3$), tetra- ($4$), penta- ($5$), hexa- ($6$), hepta- ($7$), octa- ($8$), nona- ($9$), and deca- ($10$).

Binary Acid

An aqueous acid composed of hydrogen and one other element, named by prefixing the nonmetal stem with "hydro-" and appending "-ic acid" (e.g., $HCl_{(aq)}$ is hydrochloric acid).

Oxy-Acid (Ternary Acid)

An acid containing hydrogen, oxygen, and another element, named by converting the "-ate" ending of its parent polyatomic ion to "-ic acid" (e.g., $HNO_3$ is nitric acid, derived from nitrate).

Binary Ionic Nomenclature (Fixed Charge)

The naming system for binary ionic compounds formed with main-group metals (Groups $1\text{A}$, $2\text{A}$, and $3\text{A}$), where the full element name of the cation is stated first, followed by the anion root with the suffix "-ide".

Binary Ionic Nomenclature (Variable Charge)

The naming system for transition or inner-transition metal compounds in which a Roman numeral in parentheses denotes the positive charge of the metal cation (e.g., copper (II) chloride for $CuCl_2$ and copper (I) chloride for $CuCl$).

Polyatomic Ion

A charged group of covalently bonded atoms that behaves as a single ionic unit whose combined charge must balance with counter-ions to achieve electrical neutrality.

VSEPR Theory

Valence-Shell Electron-Pair Repulsion theory, a model stating that electron pairs surrounding a central atom repel one another and arrange themselves as far apart as possible to determine molecular shapes.

Central Atom (VSEPR)

Any atom within a molecule or polyatomic ion that is directly bonded to two or more other atoms.

Electron Pair Geometry vs. Molecular Geometry

The geometric arrangement of all valence-shell electron pairs (both bonding and lone pairs) versus the geometric arrangement of only the bonded atoms; the two names differ whenever lone pairs are present on the central atom.

Molecular Shape Determination Pathway

The three-step structural progression in which a two-dimensional Lewis Structure is first drawn, followed by determining the Electron Geometry, which is then used to deduce the three-dimensional Molecular Structure.

Linear Geometry

An electron pair and molecular geometry occurring when two electron groups surround a central atom positioned $180^\circ$ opposite each other (e.g., $CO_2$).

Trigonal Planar Geometry

An electron pair geometry where three electron groups arrange themselves in a flat triangular plane around the central atom with ideal bond angles of $120^\circ$ (e.g., $CH_2O$).

Tetrahedral Geometry

An electron pair geometry where four electron groups point toward the four corners of a regular tetrahedron around the central atom with bond angles of $109.5^\circ$ (e.g., $CF_4$).

Trigonal Pyramidal Molecular Geometry

A molecular geometry resulting from four total electron pairs consisting of three bonded atoms and one lone pair ($AX_3E$), based on a tetrahedral electron pair geometry with bond angles of approximately $109.5^\circ$ (e.g., $NH_3$).

Bent (V-shaped) Molecular Geometry

A non-linear molecular shape produced either by three electron groups with two bonded atoms and one lone pair ($120^\circ$ bond angle, e.g., $NO_2^-$) or four electron groups with two bonded atoms and two lone pairs ($109.5^\circ$ bond angle, e.g., $H_2O$).