The Reactivity Series of Metals

The reactivity series ranks metals by how readily they lose electrons and form positive ions. It helps you predict reactions and explain observations. Start with the order, then use each experiment to make one comparison.

1. Definition

A. Reactivity series

A more reactive metal has a greater tendency to form positive ions. For example, magnesium loses electrons more readily than copper. This is a chemical tendency, not a claim that every magnesium sample reacts faster in every experiment.

2. Key Ideas

• Learn the required order below; hydrogen is a reference, not a metal.
• Compare reactions with water, steam and dilute hydrochloric acid under controlled conditions.
• A more reactive metal can displace a less reactive metal from its aqueous salt solution.
• Turn each displacement result into an inequality before combining results.

3. Detailed Explanations

A. The required K324 / 6092 order

Hydrogen is included to help predict reactions with dilute acids. Carbon and aluminium are useful in other contexts, but are not additional entries to memorise in this required order.

B. Deducing reactivity from evidence

If X displaces Y from an aqueous solution containing Y ions, X > Y. If Y displaces Z, Y > Z. Combining both results gives X > Y > Z. Here, > means “more reactive than”.

A single result X > Y tells you nothing about where an untested Z belongs. Distinguish an observed displacement from a colour change caused only by dilution.

C. Reactions with water, steam and dilute acid

The reaction depends on both the metal and the conditions. These observations are from controlled demonstrations; the very reactive metals require appropriate teacher handling.

With cold water, potassium, sodium and calcium form a metal hydroxide and hydrogen. For example:

Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)

With steam, magnesium forms a metal oxide and hydrogen:

Mg(s) + H₂O(g) → MgO(s) + H₂(g)

Do not use the hydroxide equation for the steam reaction. Hot iron reacts with steam to form Fe₃O₄ and hydrogen, rather than iron hydroxide.

Metals above hydrogen can displace hydrogen ions from dilute hydrochloric acid:

Magnesium loses electrons; hydrogen ions gain them to form hydrogen gas. Copper and silver lie below hydrogen and do not release hydrogen from this acid. This rule is for dilute hydrochloric acid: it is not a rule for every acid.

D. Metal displacement

Magnesium in copper(II) sulfate solution forms magnesium ions while copper ions become copper metal. The blue solution becomes paler and a reddish-brown copper deposit forms.

Mg → Mg²⁺ + 2e⁻ Cu²⁺ + 2e⁻ → Cu

Magnesium is oxidised; copper ions are reduced. Sulfate ions do not change and are omitted from the ionic equation. Copper metal cannot displace magnesium ions: that would require the less reactive metal to take the more reactive metal’s place.

For aqueous displacement comparisons, use suitable metals such as magnesium, zinc, iron and copper. Potassium and sodium react with the water itself, so putting them into a salt solution is not a clean test of metal-ion displacement.

E. Reduction of metal oxides

The next lesson explains oxide reduction and extraction. Keep this separate from hydrogen’s position in the dilute-acid comparison.

F. Thermal stability of metal carbonates

Continue with what happens when carbonates are heated.

G. Obtaining metals from ores

Learn how reactivity affects the choice of extraction method.

H. Rusting and protection of iron

Use the same series to understand why zinc and magnesium protect iron.

4. Common Mistakes

• Hydrogen is a reference, not a metal.
• The displacing metal loses electrons; the displaced metal ions gain them.
• Faster bubbling is useful evidence only when the conditions are controlled.
• No reaction with cold water does not mean no reaction with steam or dilute acid.

5. Exam Tips

State the observation, convert it into a comparison, then give the supported order. Check that your order predicts every displacement in the question.

6. Worked Examples

Modelled example 1

Use the required order

Core

Problem

Arrange magnesium, silver, lead and zinc from most to least reactive.

Study the worked solution

1. Locate each metal in the required series

   Method

   Find magnesium, zinc, lead and silver without inserting hydrogen or carbon into the answer.

   Reason

   The comparison contains metals only and uses their relative positions in the reactivity series.

   Working

   Required order includes Mg above Zn above Pb above Ag.

2. Read from most to least reactive

   Method

   Write the selected metals from higher to lower position.

   Reason

   A higher position means a greater tendency to lose electrons and form positive ions.

   Working

   magnesium > zinc > lead > silver.

Guided practice 2

Deduce from displacement

About 6 min

Problem

Metal P displaces Q from QSO₄(aq), while Q displaces R from RSO₄(aq). Deduce the reactivity order.

Convert each observation into an inequality

P displaces Q means

P > QQ > PP = Q

Combined order

P > Q > RR > Q > PQ > P > R

Check my attempt

Hints

Hint 1: use the displacement rule

A more reactive metal forms ions and displaces a less reactive metal from its salt solution.

Hint 2: link through Q

Write P > Q and Q > R on separate lines before joining them.

View solution step by step

1. Interpret the first result

   Method

   Place P above Q.

   Reason

   P can displace Q ions only if P is more reactive.

   Working

   P > Q.

2. Interpret the second result

   Method

   Place Q above R.

   Reason

   Q displaces R ions and is therefore more reactive than R.

   Working

   Q > R.

3. Combine both constraints

   Method

   Use Q as the common middle metal.

   Reason

   The two observations support one consistent chain.

   Working

   P > Q > R.

7. Mind Stretchers

Try independently: Iron is placed in copper(II) sulfate solution. Predict the observations and write the ionic equation. Then predict what happens when copper is placed in iron(II) sulfate solution.

8. Quiz