Final answer:
The correct answers are C) Halogens; Gain; Alkali metals; Lose. Alkali metals are good reducing agents because they want to lose electrons, while nonmetals, particularly halogens, make good oxidizing agents as they wish to gain electrons.
Step-by-step explanation:
Generally: metals make good reducing agents as they wish to lose electrons. Nonmetals make good oxidizing agents as they wish to gain electrons. The correct answers to fill in the blanks are C) Halogens; Gain; Alkali metals; Lose.
Metals, especially alkali metals, have low electronegativities and a few valence electrons, and they tend to lose these electrons to become cations, making them good reducing agents. On the other hand, nonmetals, and in particular halogens, have high electronegativities and a greater number of valence electrons. They gain stability by acquiring electrons to form anions, which makes them strong oxidizing agents. Within their respective groups, fluorine and oxygen are the strongest oxidizing agents.