Atom
The smallest part of an element that can exist. All substances are made up of atoms.
Atom economy
Measure of the proportion of reacting atoms that become part of the desired product in the balanced chemical equation.
Molecule
Formed from two or more atoms held together by covalent bonds.
Ion
Formed when an atom loses or gains electrons. This gives it an overall charge - a positive charge if it has lost at least one electron and a negative charge if it has gained at least one electron.
Compound
A substance that combines two or more different elements through the formation of chemical bonds.
Element
A substance that contains one type of atom only. Atoms of the same element all have the same number of protons.
Empirical formula
Smallest whole number ratio of atoms of each element in a compound.
Ionic equation
A chemical equation that involves dissociated ions.
Molar mass
Mass of one mole of a substance expressed in g/mol.
Molecular formula
The actual number of atoms of each element in a molecule.
Relative atomic mass
Average mass of an atom of an element, relative to 1/12 of the mass of an atom of carbon-12.
Relative formula mass
Average mass of a compound relative to 1/12 of the mass of an atom of carbon-12. Relative formula mass refers to compounds that have a giant structure.
Relative molecular mass
Average mass of a molecule relative to 1/12 of the mass of an atom of carbon-12.
