Chap 2: Atoms, molecules and stoichiometry

unified atomic mass unit (u)

one twelfth of the mass of a carbon-12 atom

relative atomic mass (Ar)

the ratio of the average mass of the atoms of an element to the unified atomic mass unit

relative isotopic mass

the mass of a particular atom of an isotope compared to the unified atomic mass unit

relative molecular mass (Mr)

the weighted average mass of a molecule in a given sample of that molecule compared to the the unified atomic mass unit

relative formula mass

the weighted average mass of one formula unit compared to the value of the unifed atomic mass unit

mole

the amount of substance which contain 6.02×10²³ specific particles

Avogadro constant

6.02×10²³

ionic equation

a balanced equation showing only those ions, atoms or molecules taking part in the reaction

spectator ions

ions present in a reaction mixture which do not take part in the reaction

molecular formula

the formula that shows the number and type of each atom in a molecules

empirical formula

the simplest whole number ratio of the elements present in one molecules or formula unit

water of crystallisation

a specific number of moles of water associate with a crystal structure

hydrated compound

compound which contains a definite number of moles of water in their structure

anhydrous compound

containing no water of crystallisation

percentage yield

how much of a particular product you get from the reactants compared to the maximum theoretical amount that you can get