NLN PAX Practice Exam 2025 – Complete Study Guide

The horizontal columns on the periodic chart are known as groups. This term refers to the vertical arrangements on the periodic table, which indicate elements that share similar chemical properties and behaviors due to their corresponding number of valence electrons. Elements within the same group typically exhibit comparable reactivity and tend to form similar types of compounds.

Certain characteristics of elements, such as metallic or non-metallic properties and their effective electronegativity, can often be predicted based on their group placement. For instance, Group 1 contains the alkali metals, which are highly reactive, while the noble gases in Group 18 are known for their lack of reactivity due to having full electron shells.

On the other hand, periods are the horizontal rows on the periodic table that indicate the energy levels of electrons in the atoms of the elements present in that row. Ions refer to charged particles that result from the loss or gain of electrons, and metalloids are a specific category of elements that have properties between metals and non-metals. Thus, these terms do not accurately describe the vertical columns in the periodic table.