| Anion | a negatively charged ion |
| Atom | an extremely small particle of matter that retains its identity during chemical reactions. |
| Cation | a positively charged ion. |
| Chemical change | a change in which one or more kinds of matter are transformed into a new kind |
| Compound | a substance composed of more than one element chemically combined. |
| Electron | a very light particle that carries a unit negative charge and exists in the region around the positively charge nucleus. |
| Element | a substance that cannot be decomposed by any chemical reaction into simpler substances. Type of matter composed of only one kind of atom, each atom of a given kind having the same properties. |
| Gas | the form of matter that is an easily compressible fluid; a given quantity of gas will fit into a container of any size and shape |
| Ion | an electrically charged particle obtained from an atom or a chemically bonded group of atoms by adding or removing electrons. |
| Liquid | the form of matter that is a relatively incompressible fluid; a liquid has a fixed volume, but no fixed shape. |
| Matter | whatever occupies space and can be perceived by our senses. |
| Mixture | a material that can be separated by physical means into two or more substances |
| Molecule | a definite group of atoms that are chemically bonded together-that is, tightly connected by attractive forces |
| Neutron | a particle found in the nucleus of an atom; it has a mass almost identical to that of the proton but has no electric charge. |
| Nucleus | the central core of an atom; it has most of the mass of the atom and one or more units of positive charge |
| Physical change | a change in the form of matter but not in its chemical identity. |
| Proton | a particle found in the nucleus of the atom; it has a positive electric charge equal in magnitude, but opposite in sign, to that of the electron and a mass 1836 times that of the electron |
| Solid | the form of matter characterized by rigidity; a solid is relatively incompressible and has fixed shape and volume. |