| Atom | (atomos=indivisible)The smallest piece that any element can be divided into |
| Element | A fundamental substance that can't be broken down chemically into any simpler substance |
| Metal | A malleable element with a lustrous appearance that is a good conductor of electricity |
| Non-metal | An element that is a poor conductor of heat and electricity |
| Metalloid | An element whose properties are intermediate between metal and non-metal |
| Proton | A positively charged sub-atomic particle |
| Neutron | An electrically neutral sub-atomic particle |
| Electron | A negatively charged sub-atomic particle |
| Nucleus | The dense central core of an atom that contains protons and neutrons |
| Isotopes | Atoms with identical atomic numbers, but different mass numbers |
| Electron Shell | A grouping of electrons in an atom according to energy |
| Orbital | A region of space within an atom where an electron in a given subshell can be found |
| Ion | An electrically charged atom or group of atoms |
| Cation | A positively charged ion |
| Anion | A negatively charged ion |
| Ionization energy | The energy required to remove one electron from a single ion in the gaseous state |
| Electron affinity | The energy released on adding an electron from a single ion in the gaseous state |
| Ionic bond | The electrical attraction between ions of opposite charge in a crystal |
| Polyatomic ion | An ion composed of more than one atom |
| Acid | A substance that provides H+ ions in water |
| Base | A substance that provides OH- ions in water |
| Solid | A substance that has a definite shape and volume |
| Liquid | A substance that has a definite volume, but the shape fits the container |
| Gas | A substance that has neither a definite shape or volume |
| State of matter | Physical state of a substance as a solid, liquid or gas |
| Mixture | A blend of two or more substances |
