The periodic table is just ONE table. There are not sub-tables. The periodic table is divided into periods (the horizontal rows of the table) and groups (the vertical columns). As you move horizontally across the table, an increase is the atomic number is seen, along with trends in acidity, bonding behavior, and reactivity. The groups are arranged to contain elements that have similar properties. For example, Group 1 is called the alkali earth metals group; all are light, highly reactive metals. Many more trends and groupings exist.