Final answer:
A single-replacement reaction is one in which an element replaces another element in a compound.
Step-by-step explanation:
A single-replacement reaction is one in which an element replaces another element in a compound. An element is in either the solid, liquid, or gas state and is not an ion.
For example, when sodium reacts with chlorine gas, the single-replacement reaction occurs and sodium replaces chlorine in the compound sodium chloride. The balanced chemical equation for this reaction is: 2Na + Cl₂ → 2NaCl