Defining a Group (Family) on the Periodic Table
A group, also commonly referred to as a family, represents a vertical column of elements in the periodic table. There are 18 numbered groups, each containing elements that share similar characteristics due to their atomic structure.
Shared Chemical Properties and Valence Electrons
Elements belonging to the same group typically exhibit similar chemical properties. This is primarily because they possess the same number of valence electrons—the electrons in their outermost energy shell—which dictate their chemical reactivity and how they form bonds with other elements.
Examples of Common Groups
A prominent example is Group 1, known as the Alkali Metals, which includes elements like lithium (Li), sodium (Na), and potassium (K). These elements are all highly reactive metals. Conversely, Group 18, the Noble Gases, such as helium (He) and neon (Ne), are largely unreactive because they have a full outer electron shell.
Trends Within a Group
While elements within a group share general chemical behavior, their specific properties can show gradual trends as you move down the column. For instance, atomic size generally increases, and in many groups, metallic character becomes more pronounced from the top element to the bottom.