3. GroupsMain article: Group (periodic table) A group or family is a vertical column in the periodic table. Groups are considered the most important method of classifying the elements. In some groups, the elements have very similar properties and exhibit a clear trend in properties down the group. Under the new international naming system (IUPAC), the groups are numbered numerically 1 through 18 from the left most column (the alkali metals) to the right most column (the noble gases).
