Which type of reaction is characterized by the exchange of ions between two reactants?

The described type of reaction involves the exchange of ions between two reactants, which is a defining characteristic of a double displacement reaction. In this type of reaction, the cations and anions from the reactants swap places to form new products. This often occurs in aqueous solutions where ionic compounds dissociate into their constituent ions.

For example, when sodium chloride (NaCl) reacts with silver nitrate (AgNO3), the sodium ions (Na+) and silver ions (Ag+) exchange places with the nitrate ions (NO3-) and the chloride ions (Cl-), resulting in the formation of silver chloride (AgCl) and sodium nitrate (NaNO3) in solution. This exchange effectively highlights the nature of double displacement reactions, showing how the ions interact and form new compounds.

In contrast, synthesis reactions involve combining two or more reactants to form a single product, while decomposition reactions entail a single compound breaking down into two or more simpler substances. Single displacement reactions involve one element replacing another in a compound, but do not involve the simultaneous exchange of ions from two compounds. Therefore, the double displacement reaction accurately matches the criteria described in the question.