Chapter 3: Molecules and Compounds Vocabulary

Vocabulary practice flashcards defining essential concepts, types of chemical formulas, naming conventions, and analysis techniques from Chapter 3: Molecules and Compounds.

Molecular Compound

A compound composed of nonmetal atoms held together by covalent bonds where electron pairs are shared, existing as discrete units called molecules.

Ionic Compound

A compound composed of positively charged cations (usually metals) and negatively charged anions (nonmetals) held together by electrostatic attraction in a repeating crystal lattice structure.

Molecular Formula

A chemical formula that indicates the exact number and type of atoms present in one molecule of a compound, used exclusively for molecular compounds.

Empirical Formula

A chemical formula showing the simplest whole-number ratio of elements in a compound.

Formula Unit

The smallest electrically neutral repeating unit within the crystal lattice of an ionic compound, such as one $Na^+$ and one $Cl^-$ in $NaCl$.

Classification of Pure Substances

The categorization of pure substances into elements (atomic or molecular) and compounds (molecular or ionic).

Diatomic Elements

Seven pure elements that exist naturally as two-atom molecules: $H_2$, $N_2$, $O_2$, $F_2$, $Cl_2$, $Br_2$, and $I_2$.

Polyatomic Elements

Elements whose elemental state consists of molecules containing more than two identical atoms, such as $P_4$, $S_8$, and $Se_8$.

Oxyanion

A polyatomic anion composed of oxygen combined with another element, such as $NO_3^-$ or $SO_3^{2-}$.

Hydrate

An ionic compound that contains a specific number of waters of hydration bound within its formula unit, which can be driven off by heating.

Binary Acid

An acid composed of hydrogen and a nonmetal atom (typically a halogen) in aqueous solution, named using the prefix 'hydro-', suffix '-ic', and the word 'acid'.

Oxyacid

An acid consisting of hydrogen combined with an oxyanion, named by replacing the anion ending '-ate' with '-ic' or '-ite' with '-ous', followed by 'acid'.

Inorganic Nomenclature

The system of standardized rules used to name ionic compounds, molecular compounds, binary acids, and oxyacids.

Molecular Mass

The total mass of a single molecule of a molecular compound, expressed in atomic mass units ($amu$).

Formula Mass

The mass of one formula unit of an ionic or molecular compound expressed in atomic mass units ($amu$).

Molar Mass ($M$)

The mass in grams of one mole of entities (atoms, molecules, or formula units) of a given substance, expressed in $g\,mol^{-1}$.

Mass Percent Composition

The percentage of a compound's total mass contributed by a specific element, calculated as $\text{Mass \%} = \frac{\text{mass of element in compound}}{\text{molar mass of compound}} \times 100$.

Combustion Analysis

An experimental technique where an unknown compound sample is burned completely in excess oxygen, allowing the produced $CO_2$ and $H_2O$ to be collected and weighed to determine the empirical formula.