Chemistry: Atoms, Molecules, and Ions - Section 2.4

Vocabulary practice flashcards covering chemical formulas, isomers, the mole concept, and molar mass calculations based on the Chapter 2 lecture notes.

Molecular Formula

A representation of a molecule or compound consisting of chemical symbols to indicate types of atoms and subscripts to indicate the number of each type of atom.

Structural Formula

A representation that shows the same information as a molecular formula but also illustrates how the atoms in a molecule are connected.

Diatomic Molecules

Elements that exist as molecules containing two atoms, specifically: $H_2$, $N_2$, $O_2$, $F_2$, $Cl_2$, $Br_2$, and $I_2$.

Elemental Sulfur

The most common form of sulfur, which exists as a molecule composed of eight sulfur atoms, written as $S_8$.

Empirical Formula

A formula that indicates the simplest whole-number ratio of the number of atoms (or ions) in a compound.

Isomers

Compounds that possess the same chemical formula but have different molecular structures.

Structural Isomers

Molecules with the same formula but different connections between atoms, such as acetic acid and methyl formate ($C_2H_4O_2$).

Spatial Isomers

Molecules that differ only in the relative orientations of their atoms in space, such as molecules of carvone.

Formula Mass

The sum of the average atomic masses of all atoms in a substance's formula.

Molecular Mass

A term used to correctly refer to the formula mass of a covalent substance, which exists as discrete molecules.

Formula Mass of Ionic Compounds

The sum of average atomic masses for ionic substances, which do NOT exist as molecules and therefore cannot be called molecular mass; for example, $NaCl$ is $58.44\,amu$.

The Mole

An amount unit defined as the quantity of a substance containing the same number of discrete entities as there are atoms in exactly $12\,g$ of pure carbon-12.

Avogadro’s Number ($N_A$)

The constant number of entities in a mole, determined to be $6.02214179 \times 10^{23}$, or commonly rounded to $6.022 \times 10^{23}$.

Molar Mass

The mass in grams of $1\,mol$ of a substance, expressed in units of $\text{g/mol}$, and numerically equivalent to the atomic or formula mass in $amu$.

Benzene

A clear liquid produced during oil refining with the molecular formula $C_6H_6$ and the empirical formula $CH$.

Chloroform

A covalent molecule ($CHCl_3$) with an average mass of $119.37\,amu$.

Aspirin

A molecule with the formula $C_9H_8O_4$ and an average mass of $180.15\,amu$.