| Term | Definition |
|---|---|
| Periodic table | an arrangement of the elements in order of their atomic numbers such that elements with similar properties fall in the same column, or group |
| Group | a vertical column of elements in the periodic table; elements in a group share chemical properties |
| Period | in chemistry, a horizontal row of elements in the periodic table |
| Element | is a chemical substance consisting of atoms having the same number of protons in their atomic nuclei |
| Property | characteristic of a substance that is observed during a reaction in which the chemical composition or identity of the substance is changed |
| Atom | the smallest unit of an element that maintains the properties of that element |
| Atomic mass | is the mass of an atomic particle, sub-atomic particle, or molecule |
