Last updated: 8 October 2026
Why can potassium react violently with water while copper can sit in water without any obvious reaction? Why can zinc remove copper from copper(II) sulfate solution, but copper cannot remove zinc from zinc sulfate solution? And why do we need electricity to extract magnesium while iron can be obtained using carbon?
These may look like separate pieces of Chemistry, but they are all connected by one idea: different metals have different tendencies to form positive ions. The Reactivity Series puts those tendencies into an order.
That makes the Reactivity Series much more useful than a list of names. Once you know where a metal sits in the series, you can begin to predict how it reacts with water and acids, whether displacement occurs, how easily its compounds can be reduced and even how another metal can protect iron from rusting.
Try these before reading the chapter. They check the ideas that will make the Reactivity Series much easier to understand.
- Check your starting knowledge
- Spot common misconceptions early
- Get an explanation after every answer
What Does Metal Reactivity Actually Mean?
A metal reacts when some of its atoms lose electrons and become positive ions. In a simplified form:
A highly reactive metal does this readily. Its atoms have a strong tendency to lose electrons and form positive ions.
A less reactive metal has a smaller tendency to lose electrons. This is why metals such as copper and silver take part in fewer reactions than metals such as potassium or magnesium.
The central idea behind the Reactivity Series
The higher a metal is in the Reactivity Series, the more readily its atoms lose electrons and form positive ions.
Keep returning to this idea. It explains reactions with acids, displacement reactions, extraction and sacrificial protection.
Reactivity is not exactly the same as reaction rate
It is tempting to say that a more reactive metal must always be seen reacting faster. That is too simple.
The observed rate can also be affected by temperature, surface area, concentration and protective layers on the metal. For example, an oxide coating can slow the visible reaction even though the metal itself is reactive.
The Reactivity Series describes the metal's underlying chemical tendency to form positive ions.
The Reactivity Series You Need to Know
For this topic, arrange the metals from most reactive at the top to least reactive at the bottom:
| Position | Substance | Useful clue |
|---|---|---|
| 1 | Potassium, K | Most reactive in the required list |
| 2 | Sodium, Na | Reacts vigorously with cold water |
| 3 | Calcium, Ca | Reacts readily with cold water |
| 4 | Magnesium, Mg | Reacts very slowly with cold water and readily with steam when heated |
| 5 | Zinc, Zn | Reacts with steam when strongly heated |
| 6 | Iron, Fe | Less reactive than zinc |
| 7 | Lead, Pb | Above hydrogen but often reacts slowly with dilute HCl |
| Reference | Hydrogen, H | Separates metals that normally liberate hydrogen from dilute acid from those that do not |
| 8 | Copper, Cu | Below hydrogen |
| 9 | Silver, Ag | Least reactive in the required list |
Why is hydrogen included if hydrogen is not a metal?
Hydrogen is included as a reference point.
Metals above hydrogen can normally displace H⁺ ions from dilute acids and produce H₂. Metals below hydrogen cannot normally do this.
Its position also helps us predict whether hydrogen can remove oxygen from a metal oxide.
A mnemonic for remembering the order
One possible mnemonic is:
The first letter of each word represents:
The mnemonic gets the order into your head, but that is only the first step. In an examination question, the marks usually come from using the positions to predict and explain a reaction.
How Metals React with Water and Steam
Reactions with water give us useful experimental evidence about metal reactivity. Metals near the top of the series can react with cold liquid water, while metals further down may require much more energetic conditions.
| Metal | Cold water | Steam | Main metal-containing product |
|---|---|---|---|
| Potassium | Extremely vigorous reaction | Not needed | Potassium hydroxide |
| Sodium | Vigorous reaction | Not needed | Sodium hydroxide |
| Calcium | Reacts readily | Not needed | Calcium hydroxide |
| Magnesium | Extremely slow reaction | Reacts when heated | Magnesium oxide |
| Zinc | No observable reaction | Reacts when strongly heated | Zinc oxide |
| Iron | No observable reaction | Reacts when strongly heated | Iron(II,III) oxide |
| Lead | No reaction under usual conditions | No reaction under usual O-Level conditions | — |
| Copper | No reaction | No reaction | — |
| Silver | No reaction | No reaction | — |
Potassium, sodium and calcium react with cold water
These metals are reactive enough to react directly with liquid water. The general pattern is:
For sodium:
For calcium:
The gas produced is hydrogen. A lighted splint gives the characteristic squeaky pop test.
Why do magnesium, zinc and iron need steam?
Magnesium reacts extremely slowly with cold water, while zinc and iron show no observable reaction with it. To make their reactions with water occur at a useful rate, the metal itself must be heated strongly.
This is where the steam experiment is often misunderstood.
The flame and the steam have different jobs
The Bunsen flame heats the metal strongly.
Water is boiled separately to produce steam.
The steam then passes over the hot metal and reacts with it.
The steam is therefore the reactant. It is not the source of the strong heating of the metal.
The experimental sequence is:
- Water is heated until it boils and produces steam.
- The metal is heated strongly by a Bunsen flame.
- The steam flows over the hot metal.
- The hot metal reacts with the gaseous water.
Reactions with steam
Heated magnesium reacts with steam:
Strongly heated zinc reacts similarly:
Iron also reacts with steam when strongly heated:
Why use steam instead of hot liquid water?
Zinc and iron need the metal itself to be strongly heated before their reaction with water occurs at an observable rate.
At atmospheric pressure, liquid water cannot remain liquid as its temperature rises indefinitely. At its boiling point it changes from H₂O(l) into H₂O(g).
In the experiment, water is therefore boiled separately to make steam. This gaseous H₂O can flow over the metal while a separate flame keeps the metal strongly heated.
So we should not imagine that “steam is hotter and therefore heats the metal”. The clearer picture is:
Steam → reacts with hot metal
Does H₂O(l) mean cold water?
No. The state symbol tells us the physical state, not the temperature.
- H₂O(l) means liquid water. It could be cold, warm, hot or at its boiling point.
- H₂O(g) means gaseous water.
Therefore, an equation containing H₂O(l) cannot by itself tell you whether the liquid water is cold or hot. Temperature must be stated separately.
Why does magnesium form MgO with steam instead of Mg(OH)₂?
Magnesium can react extremely slowly with liquid water to form magnesium hydroxide:
But the steam experiment is carried out under very different conditions. The magnesium is strongly heated while H₂O(g) passes over it. The overall reaction produces magnesium oxide:
There is another useful piece of Chemistry that explains why hydroxide cannot remain as the final solid under these strongly heated conditions. Magnesium hydroxide decomposes on strong heating:
What should you conclude?
We do not need to assume that Mg(OH)₂ forms first in the steam reaction.
The overall reaction is written directly as the formation of MgO. The decomposition equation simply helps us understand why Mg(OH)₂ would not remain as the final solid under strong heating.
How Metals React with Dilute Hydrochloric Acid
Hydrogen now becomes especially useful because it divides the metals into two broad groups.
- Metals above hydrogen normally react with dilute hydrochloric acid to produce hydrogen gas.
- Metals below hydrogen, such as copper and silver, do not normally react with dilute hydrochloric acid.
Example: magnesium and hydrochloric acid
If we focus only on the particles involved in the electron transfer:
Magnesium atoms lose electrons and become Mg²⁺ ions. H⁺ ions gain the electrons and eventually form H₂ molecules.
Why does the position relative to hydrogen matter?
A metal above hydrogen has a greater tendency than hydrogen to exist as positive ions. Its atoms can therefore supply electrons to H⁺ ions in the acid.
Copper and silver are below hydrogen, so they do not normally displace hydrogen from dilute hydrochloric acid.
| Metal | Behaviour with dilute HCl | Comment |
|---|---|---|
| Magnesium | Rapid effervescence | Hydrogen produced readily |
| Zinc | Steady effervescence | Usually slower than magnesium under comparable conditions |
| Iron | Slower effervescence | Fe²⁺ ions are formed |
| Lead | Very slow and may appear to stop | Lead(II) chloride can coat the metal surface |
| Copper | No reaction | Below hydrogen |
| Silver | No reaction | Below hydrogen |
Why can lead be misleading?
Lead is above hydrogen, so its position tells us that it can react with dilute hydrochloric acid. However, the reaction often becomes very slow because sparingly soluble lead(II) chloride forms on the metal surface.
This coating reduces contact between the lead and the acid. Therefore, seeing little bubbling does not mean that lead should be placed below hydrogen.
Comparing reaction rates fairly
If different metals are being compared experimentally, keep other factors constant. The metals should have similar exposed surface areas, while the acid concentration, acid volume and temperature should be the same.
Using the Reactivity Series to Predict Displacement
A displacement reaction happens when a more reactive element replaces a less reactive element in a compound.
The metal displacement rule
A more reactive metal can displace a less reactive metal from its compound.
If the added metal is less reactive, no displacement occurs.
Displacement from a solution
Suppose a zinc strip is placed in copper(II) sulfate solution. Zinc is above copper in the Reactivity Series.
Sulfate ions remain unchanged, so the ionic equation is:
Follow what happens to each metal:
- Zinc atoms lose electrons and become Zn²⁺ ions.
- Cu²⁺ ions gain electrons and become copper atoms.
The visible observations may include:
- the blue solution becomes paler as Cu²⁺ ions are removed;
- a reddish-brown deposit of copper appears;
- some zinc dissolves as Zn²⁺ ions enter the solution.
If copper is placed in zinc sulfate instead, no displacement occurs because copper is below zinc.
A common source of confusion
We say that zinc metal is more reactive than copper metal.
In the reaction, zinc atoms become Zn²⁺ while Cu²⁺ ions become copper atoms. Do not describe Cu²⁺ as the “less reactive metal”. Reactivity Series positions refer to the elements.
Why are potassium, sodium and calcium awkward in aqueous displacement experiments?
You might reason that potassium is above copper, so potassium should easily displace copper from copper(II) sulfate solution.
The problem is that copper(II) sulfate solution contains water. Potassium, sodium and calcium react readily with the water itself.
They are therefore not used like ordinary metal strips in the usual aqueous displacement experiments.
Displacement from a metal oxide
A more reactive metal can also remove oxygen from the oxide of a less reactive metal.
Magnesium is more reactive than copper:
Magnesium gains the oxygen, forming magnesium oxide. Copper(II) oxide loses oxygen and copper is formed.
The reverse reaction does not occur:
Copper is less reactive than magnesium and cannot remove oxygen from magnesium oxide.
Worked reasoning: deducing an unknown order
Suppose three metals X, Y and Z give these results:
- X displaces Y from a solution containing Y ions.
- Z displaces X from a solution containing X ions.
The first observation tells us:
The second tells us:
Combining the evidence:
This is often a better way to approach unfamiliar-metal questions: convert each observation into one comparison, then join the comparisons together.
Reducing Metal Oxides with Carbon and Hydrogen
The Reactivity Series can also tell us whether another substance can remove oxygen from a metal oxide.
Removal of oxygen is reduction.
Using carbon as a reference
Carbon is not a metal, but for extraction questions it is useful to place carbon between magnesium and zinc:
Carbon can reduce the oxides of metals below carbon in this comparison.
Example: reducing copper(II) oxide with carbon
Copper(II) oxide loses oxygen and is reduced. Carbon gains oxygen and is oxidised.
Carbon cannot reduce compounds of very reactive metals such as potassium, sodium, calcium and magnesium. These metals are above carbon.
Reduction by hydrogen
Hydrogen can remove oxygen from the oxides of metals below hydrogen.
Copper(II) oxide is an important example:
Black copper(II) oxide is reduced to reddish-brown copper.
A useful way to think about oxide reduction
A substance can remove oxygen from the oxide of a metal that is less reactive than itself in the appropriate comparison.
Carbon can reduce oxides of metals below carbon. Hydrogen can reduce oxides of metals below hydrogen.
Reactivity and the Thermal Stability of Metal Carbonates
Many metal carbonates decompose when heated. A typical carbonate forms a metal oxide and carbon dioxide:
For example, green copper(II) carbonate decomposes when heated:
The solid changes from green copper(II) carbonate to black copper(II) oxide. The CO₂ produced can be confirmed because it turns limewater milky.
What does thermal stability mean?
A thermally stable compound is difficult to decompose by heating. A less thermally stable compound decomposes more readily.
The trend you need
Carbonates of more reactive metals are generally more thermally stable.
As you move towards less reactive metals, their carbonates generally become easier to decompose by heating.
Potassium carbonate and sodium carbonate are especially thermally stable and are not decomposed by ordinary laboratory heating.
Carbonates such as calcium carbonate and copper(II) carbonate can decompose when sufficiently heated, but the less stable carbonate requires less severe conditions.
How experimental results can reveal the trend
Suppose equal amounts of two metal carbonates are heated under identical conditions.
If carbonate X produces CO₂ much sooner than carbonate Y, carbonate X is less thermally stable. The metal in X would therefore generally be expected to lie lower in the Reactivity Series than the metal in Y.
Do not turn this into an unlimited rule
The relationship here concerns the thermal stability of metal carbonates.
Do not conclude that every compound of every more reactive metal must always be more stable in every chemical situation.
How Reactivity Determines the Extraction of Metals
Many metals are found naturally as compounds in ores rather than as the elements themselves.
To obtain the metal, its positive ions must eventually be converted back into neutral metal atoms. In other words, the metal ions must be reduced.
The extraction connection
The more reactive a metal is, the more difficult it is to extract from its compounds.
Very reactive metals form positive ions readily, so converting those ions back into metal atoms requires a powerful reduction method.
| Metals | Position relative to carbon | General extraction method | Reason |
|---|---|---|---|
| Potassium, sodium, calcium, magnesium | Above carbon | Electrolysis of a molten ionic compound | Cannot be extracted by carbon reduction |
| Zinc, iron, lead | Below carbon | Reduction using carbon or carbon monoxide | Their compounds can be reduced chemically |
| Copper | Well below carbon | Relatively easy chemical reduction | Copper compounds are easier to reduce |
| Very unreactive metals | Near the bottom | May sometimes occur naturally as the element | Low tendency to react and form compounds |
Why electrolysis is required for very reactive metals
Potassium, sodium, calcium and magnesium are above carbon. Carbon cannot reduce their compounds effectively.
Electrical energy is therefore used to force positive metal ions to gain electrons:
The ionic compound is usually molten so that the ions can move and so that water is not present to interfere with the production of the highly reactive metal.
Why carbon is useful for moderately reactive metals
Zinc, iron and lead lie below carbon. Carbon or carbon monoxide can therefore be used as a reducing agent to obtain these metals from suitable compounds.
This is generally less electrically energy-intensive than electrolysis, although the use of carbon-containing reducing agents can produce carbon dioxide.
Reactivity gives the chemical reason for the method
The Reactivity Series tells us why one broad extraction method is possible and another is not.
Real industrial processes may also depend on the particular ore, cost, purity required, available energy and environmental impact.
Rusting of Iron
Corrosion is the gradual chemical destruction of a metal by substances in its surroundings. Rusting is the specific corrosion process associated with iron and steel.
Rust is mainly hydrated iron(III) oxide and can be represented approximately as Fe₂O₃·xH₂O.
The two essential conditions
Iron requires both oxygen and water to rust.
Remove either one and rusting is prevented.
How an experiment shows that both are needed
| Conditions | What is present? | Result | What it shows |
|---|---|---|---|
| Iron nail in ordinary water exposed to air | Water + oxygen | Rust forms | Both conditions together allow rusting |
| Iron nail in boiled water covered with oil | Water but little/no oxygen available | No rust | Water alone is insufficient |
| Iron nail in dry air with a drying agent | Oxygen but no water | No rust | Oxygen alone is insufficient |
Why boil the water and add an oil layer?
Boiling removes dissolved oxygen from the water. The oil layer then prevents oxygen from the air from dissolving back into the water.
This creates a situation where water is present but oxygen is effectively excluded.
Barrier methods for preventing rust
If oxygen and water cannot reach the iron surface, rusting cannot occur. This is the idea behind barrier protection.
| Method | How it works | Typical situation |
|---|---|---|
| Painting | Forms a solid barrier against oxygen and water | Gates, bridges, car bodies |
| Oiling or greasing | Forms a water-resistant barrier | Moving machine parts and chains |
| Plastic coating | Seals iron away from the surroundings | Racks and coated metal objects |
| Galvanising | Covers iron or steel with zinc | Steel sheets and outdoor structures |
Ordinary barrier methods depend on the barrier remaining intact. If paint is scratched and the iron is exposed, oxygen and water can reach the metal.
Why galvanising is more than just a barrier
Galvanising covers iron or steel with zinc. While the zinc coating is intact, it acts as a physical barrier.
But zinc has another advantage: it is more reactive than iron.
If the zinc coating is scratched, zinc can still be oxidised in preference to iron:
This protects the exposed iron as long as suitable zinc remains in electrical contact with it.
Paint compared with zinc
Paint: protects by acting as a barrier. Once the barrier is broken, the exposed iron can rust.
Zinc coating: provides a barrier and can also protect iron sacrificially because zinc is more reactive.
Sacrificial protection
Instead of coating the whole iron object, a more reactive metal can be attached to it.
Magnesium and zinc are both above iron in the Reactivity Series. They lose electrons and form positive ions more readily than iron.
The attached metal therefore corrodes in preference to the iron. It is gradually used up, which is why it is called the sacrificial metal.
Choosing a sacrificial metal
The attached metal must be more reactive than iron.
Magnesium and zinc can work. Copper cannot provide sacrificial protection because copper is less reactive than iron.
Common Mistakes in Reactivity Series Questions
Mistake 1: Treating the series as only a mnemonic
Knowing the order is only the starting point. Use the positions to explain why reactions occur.
Mistake 2: Calling hydrogen a metal
Hydrogen is a non-metal included as a useful reference point, especially for reactions with dilute acids.
Mistake 3: Thinking H₂O(l) means cold water
H₂O(l) only tells you that water is liquid. Its temperature must be stated separately.
Mistake 4: Saying steam strongly heats the metal
A Bunsen flame heats the metal. Steam is produced separately and acts as the reactant.
Mistake 5: Assuming Mg(OH)₂ must form first with steam
The overall steam reaction is written directly as Mg + H₂O(g) → MgO + H₂. Mg(OH)₂ does not need to be an intermediate.
Mistake 6: Reversing the displacement rule
A more reactive metal displaces a less reactive metal, not the other way around.
Mistake 7: Ignoring water in aqueous solutions
Potassium, sodium and calcium react readily with the water in aqueous solutions, so they are unsuitable for normal metal-ion displacement experiments.
Mistake 8: Putting lead below hydrogen
Lead is above hydrogen. Its reaction with dilute HCl may become slow because a PbCl₂ coating forms.
Mistake 9: Applying the carbonate trend to every compound
The required relationship here concerns thermal stability of metal carbonates, not every possible metal compound.
Mistake 10: Saying rusting requires air only
Both oxygen and water are essential. Dry oxygen does not cause rusting by itself.
Mistake 11: Describing galvanising as only a barrier
Zinc also provides sacrificial protection because it is more reactive than iron.
Mistake 12: Assuming more reactive always means visibly faster
Surface coatings, temperature, concentration and surface area can affect the observed reaction rate.
A Practical Checklist for Reactivity Series Questions
When faced with an unfamiliar question, work from the Reactivity Series rather than trying to remember every individual reaction.
Step 1: Identify the substances
Locate the metals involved and note whether hydrogen or carbon is being used as a reference.
Step 2: Compare their positions
Decide which metal is higher and therefore has the greater tendency to form positive ions.
Step 3: Identify the reaction type
Is the question about water, steam, acid, displacement, extraction, thermal decomposition or corrosion?
Step 4: Check the conditions
Distinguish cold liquid water from steam, and remember that H₂O(l) does not specify temperature.
Step 5: Apply the correct rule
Use the rule for that particular reaction rather than simply writing “because it is more reactive”.
Step 6: Predict the products
Work out the metal compound, displaced metal or hydrogen gas that should form.
Step 7: State observations precisely
Mention effervescence, colour changes, metal deposits, dissolving metal or rust only when they are actually expected.
Step 8: Explain the electron idea
Where useful, finish the explanation by stating that the more reactive metal forms positive ions more readily.
Now apply the Reactivity Series to unfamiliar reactions, observations and experimental evidence.
- Apply rather than simply recall
- Practise experimental reasoning
- Check why every option is right or wrong
Z displaces X²⁺
Y: CO₂ only after much longer heating
| Tube | Conditions |
|---|---|
| A | Water + air |
| B | Boiled water + oil layer |
| C | Dry air |
Frequently Asked Questions
Questions Students Often Ask About the Reactivity Series
Once the basic order is familiar, most of the interesting questions come from connecting the series with the actual conditions of a reaction.
Is hydrogen actually a metal in the Reactivity Series?
No. Hydrogen is a non-metal. It is included because its position is useful for comparison.
Metals above hydrogen normally displace H⁺ ions from dilute acids and produce H₂. Copper and silver, which lie below hydrogen, do not normally do this.
Is carbon part of the metal Reactivity Series?
Carbon is not a metal and is not one of the metals in the series you memorise.
However, it is often inserted between magnesium and zinc as an extra reference when deciding whether carbon can reduce a metal compound during extraction.
Does steam heat the metal in the steam experiment?
The metal is strongly heated directly by a Bunsen flame. Water is heated separately to make steam.
The steam then flows over the hot metal and acts as the reactant.
Steam: reacts with the hot metal
Why not just use hot water instead of steam for zinc and iron?
Zinc and iron must themselves be strongly heated before their reaction with water occurs at a useful observable rate.
At ordinary pressure, liquid water does not remain liquid once it reaches its boiling point. Water is therefore boiled to make H₂O(g), which can then be passed over the strongly heated metal.
The important point is that the flame provides the strong heating of the metal; the steam provides the H₂O that reacts.
Does H₂O(l) tell us whether the water is hot or cold?
No. The state symbol (l) tells us only that the water is liquid.
Liquid water may be cold, warm or hot. Its temperature must be specified separately. H₂O(g) means gaseous water.
Does magnesium hydroxide form first before magnesium oxide when magnesium reacts with steam?
You do not need to assume that it does. The overall steam reaction is written directly as:
Magnesium hydroxide decomposes on strong heating:
This decomposition helps explain why Mg(OH)₂ would not remain as the final solid under the strongly heated conditions.
Why can lead seem unreactive with dilute hydrochloric acid even though it is above hydrogen?
Lead can react with dilute hydrochloric acid, but sparingly soluble lead(II) chloride can coat the surface.
The coating reduces further contact between the acid and lead, so the reaction may become very slow. This does not change lead's position above hydrogen.
Why can we not simply use potassium to displace copper from copper(II) sulfate solution?
Copper(II) sulfate solution contains water. Potassium reacts violently with the water itself.
This competing reaction makes potassium unsuitable for the simple aqueous displacement experiment. Metals such as zinc or iron give much clearer displacement behaviour.
Does a more reactive metal always react faster?
Not necessarily in every experiment. The Reactivity Series describes the tendency of a metal to lose electrons and form positive ions.
The observed rate can also depend on factors such as temperature, concentration, surface area and protective oxide layers.
Why are carbonates of more reactive metals harder to decompose?
At O-Level, the important experimental trend is that carbonates of more reactive metals are generally more thermally stable.
They therefore require more severe heating before they decompose. Apply this specifically to the carbonate-stability trend rather than treating it as a rule for every type of compound.
Why are highly reactive metals more difficult to extract?
Highly reactive metals form positive ions very readily. Their ions are therefore difficult to reduce back into neutral metal atoms.
Metals above carbon cannot normally be extracted by carbon reduction and may require electrolysis of a suitable molten compound.
Why does galvanised iron remain protected even if the zinc is scratched?
Zinc is more reactive than iron. If exposed zinc remains connected to the iron, the zinc is oxidised preferentially.
The zinc therefore provides sacrificial protection in addition to acting as a physical coating.
Could copper be used as a sacrificial metal to protect iron?
No. A sacrificial metal must be more reactive than iron.
Copper lies below iron in the Reactivity Series. Magnesium or zinc is suitable because each forms positive ions more readily than iron.
The Reactivity Series becomes much easier when you stop treating water reactions, acid reactions, displacement, extraction and rust prevention as separate topics. They all grow from the same central idea: metals differ in how readily their atoms lose electrons and form positive ions. Metals near the top do this readily, while metals near the bottom do it much less readily. Once that connection is clear, the Reactivity Series becomes a tool for reasoning through unfamiliar Chemistry rather than simply another list to memorise.