Chapter 4: Molecules and Compounds chemistry

Comprehensive vocabulary flashcards covering chemical bonding types, molecular formulas, models, Lewis structures, lattice energy, nomenclature rules, and percent composition from Chapter 4.

Chemical Bond

The attraction between charged particles (electrons and protons) composing atoms that holds them together to form compounds.

Ionic Bond

A chemical bond formed between a metal and a nonmetal that involves the transfer of one or more electrons from the metal (forming a cation) to the nonmetal (forming an anion).

Covalent Bond

A chemical bond formed between two or more nonmetals that involves the sharing of electrons between atoms, resulting in the formation of a molecular compound.

Empirical Formula

A chemical formula that represents the simplest whole-number ratio of the atoms of each element present in a compound.

Molecular Formula

A chemical formula that conveys the actual number of atoms of each element present in a molecule of a compound.

Structural Formula

A diagram or sketch that uses lines to represent covalent bonds, showing the actual connectivity and spatial arrangement of atoms in a molecule.

Ball-and-Stick Molecular Model

A three-dimensional representation that depicts atoms as balls and chemical bonds as sticks, reflecting a molecule's geometric shape.

Space-Filling Molecular Model

A three-dimensional representation in which atoms fill the space between each other to approximate how a molecule would appear if scaled to visible size.

Lewis Electron-Dot Structure

A structural depiction where valence electrons are represented as dots placed around the element symbol to model chemical bonding and electron transfer or sharing.

Octet Rule

The bonding principle stating that atoms tend to gain, lose, or share electrons to attain a stable, noble gas-like electron configuration of eight valence electrons ($ns^2np^6$).

Expanded Octet

An exception to the octet rule occurring only in $p$-block elements in row 3 or later, in which a central atom accommodates 10, 12, or more valence electrons using empty $d$ orbitals.

Crystal Lattice

A three-dimensional alternating regular structure in which every cation is surrounded by anions and vice versa, maximizing electrostatic attractions without discrete molecules.

Lattice Energy

The energy released when a solid ionic crystal forms from its constituent separated ions in the gas state, which is always an exothermic value ($\Delta H^\circ$).

Type II Multivalent Cations

Metals (predominantly transition, inner transition, and select main-group metals like $\text{Pb}$, $\text{Tl}$, and $\text{Sn}$) capable of forming more than one type of ion, requiring Roman numerals in parentheses to denote their charge.

Oxyanions

Polyatomic anions containing oxygen and another element, systematically named with suffixes such as -ate for the ion with more oxygen atoms and -ite for the ion with fewer oxygen atoms.

Hydrates

Ionic compounds containing a specific stoichiometric ratio of water molecules associated with each formula unit (e.g., $\text{MgSO}_4 \cdot 7\text{H}_2\text{O}$).

Bonding Pair

A pair of valence electrons shared between two atoms to form a covalent bond.

Lone Pair

A pair of valence electrons that belongs exclusively to a single atom and is not shared in covalent bonding (also called a nonbonding pair).

Double Covalent Bond

A covalent bond formed by sharing two pairs of electrons (four electrons total) between two atoms, commonly formed by $\text{C}$, $\text{N}$, $\text{O}$, $\text{S}$, and $\text{P}$.

Triple Covalent Bond

A covalent bond formed by sharing three pairs of electrons (six electrons total) between two atoms, commonly formed by $\text{C}$, $\text{N}$, $\text{O}$, and $\text{S}$.

Percent Composition by Mass

The percentage contribution of an individual element to the total mass of a compound, calculated as: $\frac{\text{molecular mass of element } Z}{\text{mass of 1 mol of compound}} \times 100\%$.