| Term | Definition |
| Molecular Ion | Two or more atoms covalently bonded with an overall charge |
| Avogardo's Constant | Number of atoms in 12.000g of carbon-12. |
| Mole | The amount of substance which contains the Avogadro constant of atoms, molecules or groups of ions. |
| Molar Mass | The mass of one mole of substance |
| Anhydrous (salt) | A salt which contains no water of crystallisation |
| Hydrated (salt) | A salt which contains water of crystallisation |
| Water Of Crystallisation | Water chemically bonded within a crystal structure |
| Atomic Number | Number of protons in (the nucleus of) an atom |
| Mass Number | The total number of protons and neutrons in (the nucleus of) an atom |
| Relative Atomic Mass (RAM) | The average (weighted mean) mass of an atom of an element relative to one twelfth of the mass of an atom of carbon-12 |
| Relative Isotopic Mass (RIM) | The mass of an atom of an isotope of an element relative to one-twelfth of the mass of an atom of carbon-12. |
| Isotopes | Atoms which have the same atomic number but a different mass number (contain the same number of protons but a different number of neutrons) |
| Relative Formula Mass (RFM) | The average (weighted mean) mass of a formula unit relative to one-twelfth of the mass of an atom of carbon-12. |
| Relative Molecular Mass (RMM) | The average (weighted mean) mass of a molecule relative to one-twelfth of the mass of an atom of carbon-12. |
| First Ionisation Energy | The energy required to convert one mole of gaseous atoms into gaseous ions with a single positive charge. |
| Second Ionisation Energy | The energy required to convert one mole of gaseous ions with a single positive charge into gaseous ions with a double positive charge. |
| Third Ionisation Energy | The energy required to convert one mole of gaseous ions with a double positive charge into gaseous ions with a triple positive charge |
| Covalent Bond | |
| Co-ordinate (dative) Bond | |
| Octet Rule | |
| Electronegativity | |
| Polar Bond | |
| Delocalised Electrons | |
| Intermolecular | |
| Van Der Waals' Forces | |
| Permanent dipole-dipole attraction | |
| Hydrogen Bonding | |
| Redox | |
| Oxidation | |
| Reduction | |
| Oxidising Agent | |
| Reducing Agent | |
| Disproportionation | |
| Strong Acid / Base | |
| Weak Acid / Base | |
| Molarity | |
| Concentration | |
| Standard Solution | A solution for which the concentration is known |
