Reactivity Series - Reacting of elements with water, acids, and metals

Sep 5, 2026

Reactivity series explains how different elements react when exposed to water and dilute acids, organizing metals by their relative reactivity. The material covers displacement reactions, where more reactive metals replace less reactive ones in compounds, using the thermite reaction to illustrate oxidation, reduction, and large energy release. It also connects reactivity to everyday corrosion, describing rusting as an oxidation process requiring both water and oxygen, and explains multiple rust-prevention methods including coatings and galvanising with sacrificial zinc.

LanguageEnglish

CategoryExam

FormatPDF

Pages7

Reading Time18 min

AccessFree to download

Reactivity series

Reactions with water and dilute acids

Aluminium positioning and reliability of observations

Displacement reactions of metal oxides

Oxidation and reduction (redox)

Rusting and factors affecting it

Preventing rusting and galvanising

Reactivity Series Observations of the way that these elements react with water, Acids and steam enable us to put them into this series. The tables show how the elements react with water and dilute acids: | Element | Reaction with water | | --- | --- | | Potassium | Violently | | Sodium | Very quickly | | Lithium | Quickly | | Calcium | More slowly | | Element | Reaction with dilute acids | | --- | --- | | Calcium | | | Magnesium | Quickly | | Zinc | | | Iron | | | Copper | Very slowly | | Silver | Barely reacts | | Gold | Does not react | Note that aluminium can be difficult to place in the correct position in thereactivity series during these experiments. This is because its protective aluminium oxide layer makes it appear to be less reactive than it really is. When this layer is removed, the observations are more reliable. It is useful to place carbon and hydrogen into the reactivity series because these elements can be used to extract metals. Displacement reactions of metal oxides A more reactive metal will displace a less reactive metal from a compound. The thermite reaction is a good example of this. It is used to produce white hot molten (liquid) iron in remote locations for welding. A lot of heat is needed to start the reaction, but then it releases an incredible amount of heat, enough to melt theiron. aluminium + iron(III) oxide → iron + aluminium oxide 2Al + Fe2O3 → 2Fe + Al2O3 Because aluminium is more reactive than iron, it displaces iron from iron(III) oxide. The aluminium removes oxygen from the iron(III) oxide: • iron is reduced • aluminium is oxidised Reactions between metals and metal oxides allow us to put a selection of metals into a reactivity series. Using metals A, B and C: | | Metal A | Metal B | Metal C | | --- | --- | --- | --- | | A oxide | X | Displaces A | Displaces A | | B oxide | | X | | | C oxide | | Displaces C | X | Metal A cannot displace either B or C-so it must be the least reactiveand be atthe bottom of this reactivity series. Metal B displaces both A and C-so it must be the most reactive and be at the top of this reactivity series. Metal C displaces A but cannot displace B-so it must be more reactive than A but less reactive than B, and be in between them in this reactivity series. In general, the greater the difference in reactivity between two metals in a displacement reaction, the greater the amount of energy released. Aluminium is much higher than iron in the reactivity series, so the thermite reaction releases a lot of energy. Magnesium is very high in the reactivity series, and copper is very low-so the reaction between magnesium and copper oxide is more violent. Therefore, the order is: Oxidation and reduction Oxidation is the loss of electrons from a substance. It is also the gain of oxygen by a substance. For example, magnesium is oxidised when it reacts with oxygen to form magnesium oxide: magnesium + oxygen → magnesium oxide 2Mg + O2 → 2MgO Reduction is the gain of electrons by a substance. It is also the loss of oxygen from a substance. For example, copper(II) oxide can be reduced to form copper when it reacts with hydrogen: copper(II) oxide + hydrogen → copper + water CuO + H2 → Cu + H2O Usually, oxidation and reduction take place at the same time in a reaction. We call this type of reaction a redox reaction. Note that: • the oxidising agent is the chemical that causes oxidation • the reducing agent causes the other chemical to be reduced Take a look at the following thermite reaction: aluminium + iron(III) oxide → iron + aluminium oxide It is easy to see that the aluminium has been oxidised. This means that the iron oxide is the oxidising agent. We can also see that the iron oxide has been reduced. This means that the aluminium is the reducing agent. Rusting Rusting is an oxidation reaction. The iron reacts with water and oxygen to form hydrated iron(III) oxide, which we see as rust. Here is the word equation

FAQs

How does the reactivity series classify elements like potassium, sodium, and calcium?

The series ranks elements by how they react with water, showing that potassium and sodium react violently or quickly, while calcium reacts more slowly.

What is a displacement reaction and how does reactivity affect energy release?

A more reactive metal displaces a less reactive metal from a compound. The bigger the reactivity difference, the greater the energy released.

Why is rusting considered an oxidation reaction and what conditions are needed?

Rusting is oxidation of iron, requiring both water and oxygen to form hydrated iron(III) oxide (rust). Without either, rusting does not occur.

Sep 5, 2026

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