What is the term for each column in the periodic table?

Each column in the periodic table is referred to as a "group" or "family." This designation highlights the fact that elements within the same group often share similar chemical properties and exhibit similar behavior due to their equivalent number of valence electrons. For example, the elements in Group 1 (the alkali metals) are highly reactive and have one electron in their outermost shell, which is a characteristic feature that defines their reactivity.

Grouping elements this way allows for easier understanding of their relationships and trends within the table, making it a fundamental aspect of chemistry. In contrast, the other terms listed do not accurately describe columns in the periodic table; "period" refers to the rows of the table, while "series" and "category" are not standard terminology used to describe the columns.