Here's the completed paragraph based on the provided options and context:
The circle column labeled with one is called a group. There are 18 groups/families on the periodic table of elements. Elements in the same group on the periodic table are similar because they have the same number of valence electrons. This also means they have similar properties. The circle row labeled is called a period. There are 7 periods on the table. Elements in the same period are similar because they have the same number of electron shells.