The activity series of metals ranks metals from most reactive to least reactive. Students use it to predict whether a metal will replace another metal ion in a compound. This cheat sheet helps organize the ranking, reaction patterns, and evidence for single-displacement reactions.
It is especially useful for balancing equations and deciding when no reaction occurs.
A metal higher in the activity series can displace a metal lower in the series from an aqueous compound. Metals above hydrogen can react with acids to produce hydrogen gas, while metals below hydrogen usually do not. These reactions involve electron transfer, so the reacting metal is oxidized and the metal ion or hydrogen ion is reduced.
Careful use of the series prevents impossible reaction predictions.
Key Facts
- A metal higher in the activity series is more reactive and can replace a metal lower in the series from an aqueous ionic compound.
- The general single-displacement pattern is when metal is more reactive than metal .
- If metal is lower than metal in the activity series, the reaction products does not occur.
- Metals above hydrogen react with acids to form a salt and hydrogen gas, such as .
- Metals below hydrogen, such as copper, silver, gold, and platinum, usually do not produce gas with dilute acids.
- In a successful displacement reaction, the solid metal loses electrons and is oxidized, such as .
- The metal ion being displaced gains electrons and is reduced, such as .
- A balanced equation must conserve atoms and charge, so is balanced correctly.
Vocabulary
- Activity series
- A list of metals arranged from most reactive to least reactive based on their ability to lose electrons.
- Single-displacement reaction
- A reaction in which one element replaces another element in a compound, often written as .
- Oxidation
- The loss of electrons by an atom or ion, such as .
- Reduction
- The gain of electrons by an atom or ion, such as .
- Spectator ion
- An ion that remains unchanged during a reaction and does not take part in the electron transfer.
- Hydrogen gas test
- A test in which hydrogen gas makes a small pop sound when exposed to a flame, showing that was produced.
Common Mistakes to Avoid
- Reversing the activity series, which is wrong because only the metal higher on the list can replace a metal lower on the list.
- Predicting a reaction for every metal and salt mixture, which is wrong because a lower-reactivity metal cannot displace a higher-reactivity metal ion.
- Forgetting that metals above hydrogen react with acids, which leads to missing products like in equations such as .
- Writing unbalanced formulas or charges, which is wrong because ionic compounds must be electrically neutral, such as rather than .
- Ignoring oxidation and reduction, which hides the electron transfer that explains why the displacement reaction happens.
Practice Questions
- 1 Using the activity series, predict whether will react. If it reacts, write the balanced chemical equation.
- 2 Will occur? Explain using relative metal reactivity.
- 3 Balance the reaction and identify the gas produced: .
- 4 A student places silver metal into a solution of and expects zinc metal to form. Explain why this prediction is incorrect.
Understanding Activity Series of Metals
Reactivity comes from how easily atoms give up their outer electrons. Metals near the reactive end hold these electrons less tightly. When such a metal enters a solution containing ions of another metal, atoms leave the solid surface and become positive ions in the water.
Their electrons move to the ions already dissolved there. Those ions become neutral atoms and may form a new solid coating.
This is why a strip of zinc placed in blue copper sulfate solution can become coated with reddish copper. The blue color fades because copper ions are removed from the solution.
Water matters in many classroom reactions. An ionic compound must usually be dissolved so its positive and negative ions can move freely. A dry mixture of metal pieces and solid crystals may show little change because the particles cannot meet effectively.
The visible evidence is often subtle at first. Watch for a color change, metal deposits, warming, bubbles, or a metal strip becoming thinner. A deposit does not always look shiny.
It can be dark, powdery, or flaky. Recording observations before and after the reaction helps connect the equation to actual evidence.
The activity series gives a useful prediction, but real conditions can slow or hide a reaction. Aluminum is fairly reactive, yet it quickly develops a thin aluminum oxide layer. This tough coating blocks contact between the metal and the solution.
Scratching the surface can expose fresh aluminum and make the reaction clearer. Concentration, temperature, surface area, and stirring can change the reaction speed.
A prediction that a reaction can happen does not mean it will happen quickly in a small classroom experiment. Some metals react so strongly with water or acid that they require special handling and are not used in ordinary school labs.
These ideas explain several everyday effects. Iron rusts when it loses electrons in the presence of water and oxygen. Galvanizing protects steel by covering it with zinc.
If the coating is scratched, zinc can still lose electrons more readily than iron, helping protect the steel nearby. This is called sacrificial protection. Batteries use controlled electron transfer to produce electric current.
When studying reactions, first identify which substances are solids, which are dissolved ions, and which ions stay unchanged. Then track electron loss and electron gain before balancing the full equation. This method makes balancing less like guessing and makes impossible products easier to spot.