Learning Objectives Use the activity series to predict if a reaction will occur. We see two metals below that can be exposed to water. The picture on the left is of sodium, which gives a violent reaction when it comes in contact with water. The picture on the right is of silver, a metal so unreactive with water that it can be made into drinking vessels. The Activity Series 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 Ca(s) + 2H2O(l)→ Ca(OH)2 + H2 (g). These elements are very reactive and react readily to form compounds. potassium K These metals displace hydrogen from water Ca(s) + 2H2O(l)→ Ca(OH)2 + H2 (g). These elements are very reactive and react readily to form compounds. barium Ba These metals displace hydrogen from water Ca(s) + 2H2O(l)→ Ca(OH)2 + H2 (g). These elements are very reactive and react readily to form compounds. calcium Ca These metals displace hydrogen from water Ca(s) + 2H2O(l)→ Ca(OH)2 + H2 (g). These elements are very reactive and react readily to form compounds. sodium Na These metals displace hydrogen from water Ca(s) + 2H2O(l)→ Ca(OH)2 + H2 (g). These elements are very reactive and react readily to form compounds. NaN NaN These metals displace hydrogen from acids Zn(s) + HCl(aq)→ ZnCl2 + H2(g) magnesium Mg These metals displace hydrogen from acids Zn(s) + HCl(aq)→ ZnCl2 + H2(g) aluminum Al These metals displace hydrogen from acids Zn(s) + HCl(aq)→ ZnCl2 + H2(g) zinc Zn These metals displace hydrogen from acids Zn(s) + HCl(aq)→ ZnCl2 + H2(g) chromium Cr These metals displace hydrogen from acids Zn(s) + HCl(aq)→ ZnCl2 + H2(g) iron Fe These metals displace hydrogen from acids Zn(s) + HCl(aq)→ ZnCl2 + H2(g) cadmium Cd These metals displace hydrogen from acids Zn(s) + HCl(aq)→ ZnCl2 + H2(g) nickel Ni These metals displace hydrogen from acids Zn(s) + HCl(aq)→ ZnCl2 + H2(g) tin Sn These metals displace hydrogen from acids Zn(s) + HCl(aq)→ ZnCl2 + H2(g) lead Pb These metals displace hydrogen from acids Zn(s) + HCl(aq)→ ZnCl2 + 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. \[\ce{Ni} \left( s \right) + \ce{Pb(NO_3)_2} \left( aq \right) \rightarrow \ce{Ni(NO_3)_2} \left( aq \right) + \ce{Pb} \left( s \right) \nonumber \] \[\ce{Ni} \left( s \right) + \ce{Fe(NO_3)_3} \left( aq \right) \rightarrow \text{NR (no reaction)} \nonumber \] 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. Steps for Problem Solving Example \(\PageIndex{1}\) Use the activity series to predict if the reaction below will occur. If not, write \(\text{NR}\). If the reaction does occur, write the products of the reaction and balance the equation. \(\ce{Al} \left( s \right) + \ce{Zn(NO_3)_2} \left( aq \right) \rightarrow\) Example \(\PageIndex{2}\) Use the activity series to predict if the reaction below will occur. If not, write \(\text{NR}\). If the reaction does occur, write the products of the reaction and balance the equation. \(\ce{Ag} \left( s \right) + \ce{HCl} \left( aq \right) \rightarrow\) Plan the problem. Compare the placements of aluminum (the element doing the replacing) and zinc (the element being replaced) on the activity series. Compare the placements of silver (the element doing the replacing) and hydrogen (the element being replaced) on the activity series. Solve. Since aluminum is above zinc, it is capable of replacing it and a reaction will occur. The products of the reaction will be aqueous aluminum nitrate and solid zinc. Take care to write the correct formulas for the products before balancing the equation. Aluminum adopts a \(+3\) charge in an ionic compound, so the formula for aluminum nitrate is \(\ce{Al(NO_3)_3}\). The balanced equation is: \[2 \ce{Al} \left( s \right) + 3 \ce{Zn(NO_3)_2} \left( aq \right) \rightarrow 2 \ce{Al(NO_3)_3} \left( aq \right) + 3 \ce{Zn} \left( s \right) \nonumber \] Since silver is below hydrogen, it is not capable of replacing hydrogen in a reaction with an acid. \[\ce{Ag} \left( s \right) + \ce{HCl} \left( aq \right) \rightarrow \text{NR} \nonumber \] Exercise \(\PageIndex{1}\) Use the activity series to predict if the following reactions will occur. If not, write \(\text{NR}\). If the reaction does occur, write the products of the reaction and balance the equation. a. Would it be possible to store a silver spoon in a zinc nitrate solution? That is, will the following reaction occur? \Ag_{(s)} + Zn(NO_3)_{2 (aq)} → b. Would it be possible to store a silver nitrate solution in a copper container? That is, will the following reaction occur? \[Cu_{(s)} + AgNO_{3 (aq)} → Summary Metals and halogens are ranked according to their ability to displace other metals or halogens below them in the activity series.