Final answer:
An activity series lists elements based on reactivity to predict if a single-replacement reaction will occur; it happens if the free element is more reactive than the one it replaces. If feasible, a balanced chemical equation is provided.
Step-by-step explanation:
An activity series is a tool that can be used to predict whether a single-replacement reaction will occur. This series lists elements in order of their relative reactivities, with metals and nonmetals each having their separate list. When predicting reactions, a metal can only replace another metal that is below it in the activity series, and the same principle applies to nonmetals.
For example, if nickel reacts with iron (III) nitrate and lead (II) nitrate, we observe from the activity series that nickel is below iron but above lead. Thus, nickel will not replace iron in a reaction, as it's less reactive, but it will replace lead, because it is more reactive.
To predict if a single-replacement reaction will occur, we compare the reactivity of the elements involved. If the free element is more reactive than the element it attempts to replace in the compound, the reaction will occur. If not, the reaction will not take place, and we write 'NR' for no reaction. When a reaction is feasible, the correct balanced chemical equation should be written to represent the reaction's stoichiometry.