Foundations of Chemistry

Subtopics 1-3

Proton

A positively charged subatomic particle found in the nucleus of an atom.

Neutron

An uncharged subatomic particle found in the nucleus of an atom.

Electron

A negatively charged subatomic particle found in orbitals around the nucleus.

Atomic number

The number of protons in the nucleus of an atom.

Mass number

The total number of protons and neutrons in the nucleus of an atom.

Isotope

Atoms of the same element with the same number of protons but different numbers of neutrons.

Relative isotopic mass

The mass of an atom of an isotope compared with one-twelfth of the mass of a carbon-12 atom.

Relative atomic mass

The weighted mean mass of an atom of an element compared with one-twelfth of the mass of a carbon-12 atom.

Relative molecular mass

The mass of a molecule compared with one-twelfth of the mass of a carbon-12 atom.

Ion

An electrically charged particle formed when an atom or group of atoms gains or loses electrons.

Cation

A positively charged ion formed by the loss of electrons.

Anion

A negatively charged ion formed by the gain of electrons.

Element

A substance consisting of atoms that all have the same number of protons.

Compound

A substance containing two or more different elements chemically bonded together in fixed proportions.

Molecule

Two or more atoms covalently bonded together.

Ionic bond

The strong electrostatic attraction between oppositely charged ions.

Ionic compound

A compound consisting of positive and negative ions held together by electrostatic attraction.

Chemical formula

A representation showing the elements present in a substance and their relative numbers of atoms or ions.

Balanced chemical equation

An equation in which the number of atoms of each element is equal on both sides.

Ionic equation

An equation showing only the ions or particles that take part in a reaction.

State symbol

A symbol indicating the physical state of a substance in a chemical equation.

Relative formula mass

The sum of the relative atomic masses of all the atoms in a formula unit.

Aqueous

A substance dissolved in water.

Disproportionation reaction

A reaction in which an element is simultaneously oxidised and reduced.

Amount of substance

The quantity of a substance measured in moles.

Mole

The unit of amount of substance; one mole contains 6.02 × 10²³ specified particles.

Avogadro constant

The number of particles in one mole of a substance (6.02 × 10²³ mol⁻¹).

Molar mass

The mass of one mole of a substance, measured in g mol⁻¹.

Molar gas volume

The volume occupied by one mole of a gas at a specified temperature and pressure.

Empirical formula

The simplest whole-number ratio of atoms of each element present in a compound.

Molecular formula

The actual number and type of atoms present in a molecule.

Anhydrous

A substance that contains no water of crystallisation.

Hydrated

A substance containing water of crystallisation within its crystal structure.

Water of crystallisation

Water molecules incorporated into the crystal structure of a compound.

Concentration

The amount of solute dissolved per unit volume of solution.

Standard solution

A solution of accurately known concentration.

Percentage yield

The actual yield divided by the theoretical yield, multiplied by 100.

Atom economy

The relative mass of the desired product compared with the total relative mass of all products, expressed as a percentage.

Limiting reagent

The reactant that is completely used up first and determines the maximum amount of product formed.

Excess reagent

A reactant present in a greater amount than is required to react completely with the other reactant.

Stoichiometry

The quantitative relationship between reactants and products in a chemical reaction.

Acid

A proton donor.

Base

A proton acceptor.

Alkali

A soluble base that produces OH⁻ ions in aqueous solution.

Strong acid

An acid that completely ionises in aqueous solution.

Weak acid

An acid that only partially ionises in aqueous solution.

Monoprotic acid

An acid that releases one mole of H⁺ ions for every mole of acid that ionises completely.

Diprotic acid

An acid that can release two moles of H⁺ ions for every mole of acid that ionises completely.

Triprotic acid

An acid that can release three moles of H⁺ ions for every mole of acid that ionises completely.

Neutralisation

The reaction between an acid and a base to form a salt; an acid–alkali reaction also produces water.

Salt

An ionic compound formed when the hydrogen ions of an acid are replaced by metal ions or ammonium ions.

Acid salt

A salt formed when only some of the replaceable hydrogen ions in a polyprotic acid are replaced by metal or ammonium ions.

Conjugate acid

The species formed when a base accepts a proton.

Conjugate base

The species formed when an acid donates a proton.

pH

A measure of the hydrogen ion concentration of an aqueous solution, defined as −log₁₀[H⁺].

Equivalence point

The point in a titration at which the reactants have reacted in the exact stoichiometric proportions shown by the equation.

Indicator

A substance that changes colour over a particular pH range.

Titration

A technique used to determine the concentration of a solution by reacting it with a solution of known concentration.