A charged group of atoms that functions as a single unit in a chemical reaction is called?

The term that accurately describes a charged group of atoms functioning as a single unit in a chemical reaction is a polyatomic ion. A polyatomic ion consists of two or more atoms bonded together that collectively have a positive or negative charge due to the loss or gain of electrons. This characteristic allows them to participate in chemical reactions just like individual ions, but as a group.

In the context of chemical reactions, polyatomic ions can form bonds with other ions or molecules. For instance, they can combine with metals to create ionic compounds or interact with other compounds in various chemical processes. Their behavior in reactions is distinct because their charge affects how they bond and interact with different substances.

Other terms provided, such as molecular compounds, ionic compounds, and elements, refer to different concepts in chemistry. A molecular compound is typically made up of two or more nonmetals sharing electrons but does not necessarily refer to a charged group. An ionic compound generally refers to the resulting compound formed between cations and anions, which can include polyatomic ions but is broader in scope. An element signifies a substance that cannot be broken down into simpler forms and represents only one type of atom. Thus, polyatomic ion is the most precise term reflecting the description given in the question.