The Reactivity Series
AdvancedMetals rank by reactivity: K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu > Ag > Au. The more reactive, the more readily it reacts with oxygen, water and acids. A more reactive metal displaces a less reactive one from its salt solution (e.g. iron nail in copper sulphate forms copper).
- Series: K Na Ca Mg Al · Zn Fe Pb Cu · Ag Au
- More reactive = reacts/oxidises more easily
- Displacement: more reactive kicks out less reactive
§Text Passage
1Metals differ enormously in reactivity: potassium and sodium react violently the moment they touch water, while gold and silver stay almost unchanged for centuries. Scientists rank metals by vigour of reaction, from strongest to weakest — the reactivity series: K, Na, Ca, Mg, Al, Zn, Fe, Pb, then Cu, Ag, Au. Hydrogen, though not a metal, sits between lead and copper as a reference line for judging which metals react with dilute acids.
2The higher a metal stands, the more readily it reacts with oxygen and water. Potassium and sodium are so reactive that they must be stored under oil, cut off from the air; magnesium burns with a dazzling white light; copper only slowly blackens on heating, forming black copper oxide. The conditions for reacting with water grow harsher down the series: potassium, sodium and calcium react with cold water at room temperature, magnesium needs hot water for a visible reaction, and copper, silver and gold do not react with water at all.
3Only metals above hydrogen react with dilute acids and give off hydrogen gas, the higher ones more vigorously; copper, silver and gold lie below hydrogen, which is why dilute acid can be kept in copper vessels. The series also predicts displacement: a more reactive metal pushes a less reactive metal out of its compound solution. Place an iron nail in blue copper sulphate solution and iron, being more reactive, displaces copper: a red-brown coat of copper forms on the nail while the solution turns from blue to pale green; put copper into iron sulphate solution instead and nothing happens.
4The series also decides how metals occur in nature and how they are extracted. Unreactive gold and silver exist as native elements; zinc and iron occur as ores and are extracted by heating with carbon; still more reactive metals such as aluminium need electrolysis. The more reactive the metal, the harder the extraction — aluminium is actually more abundant than iron in the crust, yet it was only used on a large scale after electrolysis was invented in the nineteenth century.
1Summary 重點摘要
Metals rank by reactivity: K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu > Ag > Au. The more reactive, the more readily it reacts with oxygen, water and acids. A more reactive metal displaces a less reactive one from its salt solution (e.g. iron nail in copper sulphate forms copper).
2Vocabulary cards Vocabulary
The ranking of metals from most to least reactive.
A more reactive metal 'kicks out' a less reactive one from its compound.
The product of a metal combining with oxygen, e.g. copper oxide (CuO).
Rarely reacts — like gold and silver.
Reaction of a metal with oxygen — the more reactive, the more easily oxidised.
An acid used to test reactivity — metals above hydrogen react with it, releasing hydrogen gas.
The reference point in the series — only metals above it react with dilute acids.
Very unreactive metals (gold, silver) occurring pure in nature.
3Step by step Steps
- Learn the seriesThe mnemonic 'K, Na, Ca, Mg, Al, Zn, Fe, Pb, then Cu, Ag, Au' lists the metals in falling reactivity: the further left, the more reactive the metal. Hydrogen, though not a metal, sits between lead and copper as a reference line deciding which metals react with dilute acids. Learning this order by heart underpins every judgement about how metals react with oxygen, water and acids, and whether a displacement can happen — every question in the topic is built on it.
- With oxygenThe more reactive the metal, the more readily it combines with oxygen: potassium and sodium are so reactive that they must be stored under oil, cut off from the air; magnesium burns with a dazzling white light; copper only slowly blackens on heating; gold and silver are so unreactive that they occur native — which is exactly why ancient people could pick natural gold nuggets straight from riverbeds. The vigour of the reactions lines up neatly with the series, from strong to weak.
- With waterPotassium, sodium and calcium react with cold water at room temperature — potassium and sodium melt into little balls that dart about on the surface; magnesium needs hot water for a visible reaction, and iron reacts only slowly with high-temperature steam; copper, silver and gold do not react with water at all. The conditions clearly grow harsher as reactivity falls, making these experimental observations important evidence for judging reactivity and common material for ordering questions.
- With acidOnly metals above hydrogen in the series — potassium through to lead — react with dilute acids and give off hydrogen gas; the higher the metal, the more vigorous the reaction. Copper, silver and gold sit below hydrogen and do not react at all, which is why dilute acid can be kept in copper vessels. How quickly bubbles appear in the experiment is the usual way to compare metals' reactivity, and the basis for answering practical ordering questions.
- Displacement conditionDisplacement follows a single rule: a more reactive metal pushes a less reactive metal out of its compound solution. Iron is more reactive than copper, so it displaces copper from copper sulphate solution; the reverse never happens — copper cannot displace iron. In these questions always check the series before writing; reversing the direction is the classic error. Just remember: the reactive one ousts the unreactive one, and the marks are safe.
- Reactivity and extractionThe series decides how metals occur in nature and how hard they are to extract: unreactive gold and silver exist as native elements; zinc and iron occur as ores (compounds) and are extracted by heating with carbon; still more reactive metals such as aluminium need electrolysis. The more reactive the metal, the harder the extraction — aluminium is actually more abundant than iron in the crust, yet humans only used it on a large scale after electrolysis was invented in the nineteenth century.
4Diagrams Diagrams
5Worked example Example
An iron nail is placed in blue copper sulphate solution. What happens?
- Series: iron > copper
- Iron displaces copper from copper sulphate
- Blue colour fades (copper ions used up); red-brown copper coats the nail
- Equation: Fe + CuSO₄ → FeSO₄ + Cu
- Answer: Iron is more reactive than copper, so it displaces copper from the solution: a red-brown coat of copper builds up on the nail, while the solution turns from blue to pale green as blue copper ions are used up and iron sulphate forms. Equation: Fe + CuSO₄ → FeSO₄ + Cu. Score by writing the chain: iron more reactive → displacement → colour change + deposit.
6Common mistakes Mistakes
7Quick check Quick check
Q1Which is more reactive: zinc or copper?
Q2Does magnesium react with iron sulphate solution?
Q3Why can gold be found in nature as nuggets?
Q4Does a piece of copper release hydrogen in dilute sulphuric acid? Why?
Q5Why are potassium and sodium stored under oil?
8Recap Recap
- Series: K Na Ca Mg Al · Zn Fe Pb Cu · Ag Au
- More reactive = reacts/oxidises more easily
- Displacement: more reactive kicks out less reactive
- Only metals above hydrogen react with dilute acid, releasing hydrogen
- K and Na are stored in oil; gold and silver occur native