Single-replacement reactions only occur when the element that is doing the replacing is more reactive than the element that is being replaced. Therefore, it is useful to have a list of elements in order of their relative reactivities. The activity series is a list of elements in decreasing order of their reactivity. Since metals replace other metals, while nonmetals replace other nonmetals, they each have a separate activity series. The table below is an activity series of most common metals and of the halogens. Most Active (Easily Oxidized—Readily Lose Electrons) Most Active (Easily Oxidized—Readily Lose Electrons).1 Most Active (Easily Oxidized—Readily Lose Electrons).2 lithium Li These metals displace hydrogen from water \( \ce{Ca}(s) + 2\;\ce{H2O}(l) \rightarrow \ce{Ca(OH)2}(aq) + \ce{H2}(g) \). These elements are very reactive and react readily to form compounds. potassium K These metals displace hydrogen from water \( \ce{Ca}(s) + 2\;\ce{H2O}(l) \rightarrow \ce{Ca(OH)2}(aq) + \ce{H2}(g) \). These elements are very reactive and react readily to form compounds. barium Ba These metals displace hydrogen from water \( \ce{Ca}(s) + 2\;\ce{H2O}(l) \rightarrow \ce{Ca(OH)2}(aq) + \ce{H2}(g) \). These elements are very reactive and react readily to form compounds. calcium Ca These metals displace hydrogen from water \( \ce{Ca}(s) + 2\;\ce{H2O}(l) \rightarrow \ce{Ca(OH)2}(aq) + \ce{H2}(g) \). These elements are very reactive and react readily to form compounds. sodium Na These metals displace hydrogen from water \( \ce{Ca}(s) + 2\;\ce{H2O}(l) \rightarrow \ce{Ca(OH)2}(aq) + \ce{H2}(g) \). These elements are very reactive and react readily to form compounds. NaN NaN These metals displace hydrogen from acids \( \ce{Zn}(s) + \ce{HCl}(aq) \rightarrow \ce{ZnCl2}(aq) + \ce{H2}(g) \) magnesium Mg These metals displace hydrogen from acids \( \ce{Zn}(s) + \ce{HCl}(aq) \rightarrow \ce{ZnCl2}(aq) + \ce{H2}(g) \) aluminum Al These metals displace hydrogen from acids \( \ce{Zn}(s) + \ce{HCl}(aq) \rightarrow \ce{ZnCl2}(aq) + \ce{H2}(g) \) zinc Zn These metals displace hydrogen from acids \( \ce{Zn}(s) + \ce{HCl}(aq) \rightarrow \ce{ZnCl2}(aq) + \ce{H2}(g) \) chromium Cr These metals displace hydrogen from acids \( \ce{Zn}(s) + \ce{HCl}(aq) \rightarrow \ce{ZnCl2}(aq) + \ce{H2}(g) \) iron Fe These metals displace hydrogen from acids \( \ce{Zn}(s) + \ce{HCl}(aq) \rightarrow \ce{ZnCl2}(aq) + \ce{H2}(g) \) cadmium Cd These metals displace hydrogen from acids \( \ce{Zn}(s) + \ce{HCl}(aq) \rightarrow \ce{ZnCl2}(aq) + \ce{H2}(g) \) nickel Ni These metals displace hydrogen from acids \( \ce{Zn}(s) + \ce{HCl}(aq) \rightarrow \ce{ZnCl2}(aq) + \ce{H2}(g) \) tin Sn These metals displace hydrogen from acids \( \ce{Zn}(s) + \ce{HCl}(aq) \rightarrow \ce{ZnCl2}(aq) + \ce{H2}(g) \) lead Pb These metals displace hydrogen from acids \( \ce{Zn}(s) + \ce{HCl}(aq) \rightarrow \ce{ZnCl2}(aq) + \ce{H2}(g) \) NaN NaN NaN hydrogen H NaN NaN NaN NaN copper Cu These metals do not displace hydrogen from acids or water. These elements are more stable, and form compounds less readily than do those higher in the table. silver Ag These metals do not displace hydrogen from acids or water. These elements are more stable, and form compounds less readily than do those higher in the table. mercury Hg These metals do not displace hydrogen from acids or water. These elements are more stable, and form compounds less readily than do those higher in the table. platinum Pt These metals do not displace hydrogen from acids or water. These elements are more stable, and form compounds less readily than do those higher in the table. gold Au These metals do not displace hydrogen from acids or water. These elements are more stable, and form compounds less readily than do those higher in the table. Least Active Least Active Least Active For a single-replacement reaction, a given element is capable of replacing an element that is below it in the activity series. This can be used to predict if a reaction will occur. Suppose that small pieces of the metal nickel were placed into two separate aqueous solutions: one of iron (III) nitrate and one of lead (II) nitrate. Looking at the activity series, we see that nickel is below iron, but above lead. Therefore, the nickel metal will be capable of replacing the lead in a reaction, but will not be capable of replacing iron. \[\ce{Ni} \left( s \right) + \ce{Pb(NO3)2} \left( aq \right) \rightarrow \ce{Ni(NO3)2} \left( aq \right) + \ce{Pb} \left( s \right) \nonumber \] \[\ce{Ni} \left( s \right) + \ce{Fe(NO3)3} \left( aq \right) \rightarrow \text{NR (no reaction)} \nonumber \] In the descriptions that accompany the activity series of metals, a given metal is also capable of undergoing the reactions described below that section. For example, lithium will react with cold water, replacing hydrogen. It will also react with steam and with acids, since that requires a lower degree of reactivity.