What defines a displacement reaction?

A displacement reaction, also known as a substitution reaction, is characterized by one element replacing another element in a compound. This process typically occurs in reactions where a more reactive element displaces a less reactive one. For example, in the reaction of zinc with hydrochloric acid, zinc displaces hydrogen from the acid to form zinc chloride and hydrogen gas. This type of reaction is fundamental in understanding how elements interact and change chemical compounds during chemical processes.

The other options focus on different types of chemical reactions. Acids reacting with bases typically result in neutralization reactions, while the interaction of two metals can lead to various outcomes but is not specific to displacement. The reaction of two nonmetals forming ionic compounds is also a distinct type of interaction, but it does not encapsulate the concept of one element taking the place of another in a compound, which is central to the definition of displacement reactions.