Which element group is characterized by their tendency to gain electrons during reactions?

The group characterized by their tendency to gain electrons during reactions is nonmetals. Nonmetals have high electronegativities and a greater tendency to attract electrons compared to metals. This property enables them to form anions, which are negatively charged ions created when nonmetals gain one or more electrons.

In contrast, metalloids exhibit properties intermediate between metals and nonmetals, and their behavior can vary widely in terms of electron gain and loss during reactions. Alkali metals are highly reactive metals that typically lose electrons, resulting in a positive charge, while metals in general also tend to lose electrons during reactions to become cations. Hence, the distinctive behavior of nonmetals in gaining electrons is what sets them apart in this context.