CHY-103 Chapter 3: Molecules, Compounds, and Nomenclature

Vocabulary flashcards covering chemical formulas, molecular models, ionic compounds, element classification, formula mass, mass percentage, CHNS analysis, and molecular formula calculations based on General Chemistry I lectures.

Molecule

A definite group of atoms that are chemically bonded together.

Molecular Formula

An abbreviated description of the composition of a molecule that indicates the actual numbers and types of atoms in a molecule.

Empirical Formula

A chemical formula that gives the relative, simplest whole-number ratio of numbers and types of atoms in a molecule or compound.

Ionic Compound

A compound consisting of cations (positive charge) and anions (negative charge) associated to give an overall neutral species, generally formed from a combination of metal and nonmetal elements.

Ion

A charged species formed when a neutral atom gains or loses one or more electrons.

Anion

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

Cation

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

Element

A substance consisting of only one kind of atom in the form of a molecule or individual atom that cannot be decomposed into simpler substances by ordinary chemical means.

Compound

A substance consisting of two or more kinds of atoms that form a molecule or molecular entity with properties different than its components.

Molecular Compound

A compound composed of elements (not ions) held together by covalent bonds, represented by a molecular formula.

Atomic Element

An element that exists in nature with single individual atoms as its basic units, such as neon ($Ne$).

Molecular Element

An element that exists in nature as molecules composed of two or more atoms of the same element chemically bonded together, such as oxygen ($O_2$), phosphorus ($P_4$), or sulfur ($S_8$).

Formula Mass

The sum of the atomic masses of all atoms in a chemical formula, expressed in atomic mass units ($amu$); synonymous with molecular mass and molecular weight.

Molar Mass

The mass in grams of one mole of a substance, expressed in units of $g\,mol^{-1}$, which is numerically equal to its formula mass in $amu$.

Mass Percentage of an Element

The percent contribution of an element to the total mass of a compound, calculated as: $\text{mass \% of element X} = \frac{\text{mass of element X in } 1\,\text{mol of compound}}{\text{mass of } 1\,\text{mol of compound}} \times 100$

CHNS Analysis

An elemental analysis technique where a sample is oxidized (combusted) in $O_2$ at high temperature ($1000\,^\circ\text{C}$), converting carbon to $CO_2$, hydrogen to $H_2O$, nitrogen to $N_2$, and sulfur to $SO_2$.

Formula Unit

The simplest neutral empirical unit representing the ratio of ions in an ionic compound, such as $NaCl$.

Molecular Formula Molar Mass Relationship

The mathematical relationship used to determine a compound's molecular formula from its empirical formula: $\text{molar mass} = n \times \text{empirical formula molar mass}$, where $n$ is an integer multiplier.

Procaine

A pain killer used by dentists with the molecular formula $C_{13}H_{20}N_2O_2$.

Aniline

A starting compound of urethane plastic foams consisting of carbon, hydrogen, and nitrogen with a molar mass of $93.12\,g\,mol^{-1}$ and molecular formula $C_6H_7N$.