Empirical Formula

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Empirical Formula Noun

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[em-peer-i-kuhl for-myoo-luh]

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Empirical Formula

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A chemical formula representing the simplest whole-number ratio of atoms or moles of elements present in a chemical compound.

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Example: This table shows how an empirical formula is the simplest whole-number ratio of atoms in a compound, derived by simplifying the subscripts of the molecular formula.

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Molecular Formula Noun

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[muh-lek-yuh-ler for-myoo-luh]

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Molecular Formula

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A chemical formula that shows the true or total number of atoms of each element present in a single molecule.

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Example: This table shows that a molecular formula (like C6H12O6 for glucose) gives the actual atom count, while an empirical formula (CH2O) shows the simplest ratio.

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Percent Composition Noun

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[per-sent kom-puh-zish-uhn]

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Percent Composition

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The percentage by mass of each individual element that is present within a chemical compound.

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Example: This image shows a step-by-step calculation of percent composition for a molecule, dividing each element's mass by the total molecular mass to find its percentage.

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Molar Mass Noun

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[moh-ler mas]

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Molar Mass

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The mass of one mole of a substance, typically expressed in grams per mole, used to convert between mass and moles.

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Example: The molar mass of a compound (like H₂O) is calculated by adding the atomic masses of each atom in the molecule (two hydrogens plus one oxygen).

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Mole Noun

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[mohl]

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Mole

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A standard scientific unit for measuring large quantities of very small entities such as atoms, molecules, or other specified particles.

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Example: This diagram defines one mole by showing it is equivalent to 12 grams of carbon-12, which contains Avogadro's number (602 sextillion) of atoms.

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Subscript Noun

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[suhb-skript]

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Subscript

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A number written immediately after and slightly below a chemical symbol, indicating the number of atoms of that element in a formula.

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Example: The subscript '4' in the chemical formula CH₄ indicates there are four hydrogen atoms (green spheres) bonded to one carbon atom (orange sphere).

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Ionic Compound Noun

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[ahy-on-ik kom-pound]

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Ionic Compound

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A chemical compound composed of ions, for which the chemical formula is always an empirical formula representing the simplest ratio.

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Example: A sodium atom transfers an electron to a chlorine atom, creating charged ions (Na+ and Cl-) that attract to form an ionic compound, NaCl.

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Molecular Compound Noun

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[muh-lek-yuh-ler kom-pound]

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Molecular Compound

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A compound composed of individual molecules, whose chemical formula can be either empirical or a multiple of the empirical formula.

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Example: This image shows a model of a carbon dioxide (CO2) molecule, a common molecular compound where atoms are joined by covalent bonds.

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Empirical Formula Mass Noun

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[em-peer-i-kuhl for-myoo-luh mas]

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Empirical Formula Mass

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The sum of the average atomic masses of all the atoms that are represented in a compound's empirical formula.

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Example: This image shows how to calculate the empirical formula mass by adding the atomic masses of each atom in the empirical formula (CH₂O).

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Molecular Formula Mass Noun

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[muh-lek-yuh-ler for-myoo-luh mas]

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Molecular Formula Mass

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The mass of a single molecule of a substance, calculated by summing the atomic masses of all atoms in its molecular formula.

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Example: This image shows a methane molecule (CH₄), which has one carbon and four hydrogen atoms. Its molecular formula mass is calculated from these atoms.