| A | B |
|---|
| Triad | a group of three elements with similar properties |
| Law of Octaves | the same properties appear every 8 elements when elements are listed in order of their atomic masses |
| Periodic Table | pictorial arrangement of the element based on their atomic numbers and electron configurations |
| Transition Elements | an element whose highest energy electron is in the d sublevel |
| Lanthanoid Series | fourteen elements beginning with lanthanum in which the arrow diagram predicts the highest energy electrons to be in the 4f sublevel. |
| Actinoid Series | fourteen elements beginning with actium in which the arrow diagram predicts the highest energy electrons to be in the 5f sublevel. |
| Period | horizontal row in the Periodic Table. |
| Group | elements of a vertical column of the Periodic Table. |
| Octet Rule | tendency of atoms to gain or lose electrons so they acquire 8 electrons in their outer most level. |
| Family | the elements composing of a vertical column of the Periodic Table. |
| Metal | element that tends to lose electrons in chemical reactions. |
| Nonmetals | elements that tend to gain electrons in chemical reactions. |
| Metalloid | element that has properties characteristics of metals and nonmetals. |
| Periodic Law | the properties of the elements are a periodic function of their atomic numbers. |
