What are the vertical columns on the periodic table called?

The vertical columns on the periodic table are known as groups or families. This terminology reflects the fact that elements within a group often exhibit similar chemical properties and behaviors due to their comparable valence electron configurations. For example, the elements in Group 1, known as the alkali metals, share characteristics such as being highly reactive and having one electron in their outer shell.

In contrast, periods refer to the horizontal rows of the periodic table, where elements are organized by increasing atomic number and illustrate trends in properties such as electronegativity and atomic size across a row. Series and rows are not commonly used terms in the context of the periodic table to describe vertical columns, which reinforces the appropriateness of the term "groups" or "families" for these vertical arrangements.