The Reactivity Series

This lesson covers the reactivity series as required by the Edexcel GCSE Chemistry specification (1CH0), Topic 4: Extraction of Metals and Equilibria. You need to know the order of metals in the reactivity series, understand how it is determined experimentally, and recall the reactions of metals with water and dilute acids.

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What Is the Reactivity Series?

The reactivity series is a list of metals arranged in order of their reactivity, from the most reactive at the top to the least reactive at the bottom. It is determined by observing how vigorously metals react with water, dilute acids and oxygen.

Carbon and hydrogen are included as reference points, even though they are non-metals. Their positions are important for understanding metal extraction and acid reactions.

graph TD
    subgraph "The Reactivity Series"
    K["<b>Potassium (K)</b> — Most reactive"]
    Na["<b>Sodium (Na)</b>"]
    Ca["<b>Calcium (Ca)</b>"]
    Mg["<b>Magnesium (Mg)</b>"]
    Al["<b>Aluminium (Al)</b>"]
    C["<b>Carbon (C)</b> ← reference"]
    Zn["<b>Zinc (Zn)</b>"]
    Fe["<b>Iron (Fe)</b>"]
    H["<b>Hydrogen (H)</b> ← reference"]
    Cu["<b>Copper (Cu)</b>"]
    Ag["<b>Silver (Ag)</b>"]
    Au["<b>Gold (Au)</b>"]
    Pt["<b>Platinum (Pt)</b> — Least reactive"]
    end

    K --> Na --> Ca --> Mg --> Al --> C --> Zn --> Fe --> H --> Cu --> Ag --> Au --> Pt

    style K fill:#e74c3c,color:#fff
    style Na fill:#e74c3c,color:#fff
    style Ca fill:#e67e22,color:#fff
    style Mg fill:#e67e22,color:#fff
    style Al fill:#f1c40f,color:#000
    style C fill:#95a5a6,color:#fff
    style Zn fill:#f1c40f,color:#000
    style Fe fill:#f1c40f,color:#000
    style H fill:#95a5a6,color:#fff
    style Cu fill:#3498db,color:#fff
    style Ag fill:#3498db,color:#fff
    style Au fill:#3498db,color:#fff
    style Pt fill:#3498db,color:#fff

Exam Tip: Learn a mnemonic for the reactivity series. A common one is: Please Stop Calling Me A Clever Zebra, Instead Help Carry Some Gold Please. (Potassium, Sodium, Calcium, Magnesium, Aluminium, Carbon, Zinc, Iron, Hydrogen, Copper, Silver, Gold, Platinum.)

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How Is the Reactivity Series Determined?

The position of a metal in the reactivity series is determined by observing its reactions in several experiments:

1. Reactions with Water

Metals above magnesium in the reactivity series react with cold water. Magnesium reacts very slowly with cold water but vigorously with steam.

General equation:

metal + water → metal hydroxide + hydrogen

Metal	Reaction with Cold Water	Observations
Potassium	Very vigorous	Floats, catches fire with lilac flame, melts, moves rapidly, may explode
Sodium	Vigorous	Floats, melts into a ball, moves across surface, fizzes rapidly
Lithium	Moderate	Floats, fizzes steadily, gradually dissolves
Calcium	Moderate	Sinks, steady stream of bubbles, water turns milky
Magnesium	Very slow	Extremely slow with cold water; reacts well with steam
Zinc	No reaction	No visible change with cold water
Iron	No reaction	No visible change (though iron rusts slowly in moist air)
Copper	No reaction	No visible change

2. Reactions with Dilute Acid

Metals above hydrogen in the reactivity series react with dilute hydrochloric acid or dilute sulfuric acid.

General equation:

metal + acid → salt + hydrogen

Metal	Reaction with Dilute HCl	Observations
Magnesium	Very vigorous	Rapid fizzing, metal dissolves quickly, solution warms up noticeably
Aluminium	Moderate (once oxide layer removed)	Fizzes, but may be slow to start due to oxide layer
Zinc	Moderate	Steady fizzing, metal dissolves gradually
Iron	Slow	Slow fizzing, metal dissolves very slowly, solution turns pale green
Copper	No reaction	No fizzing, metal remains unchanged
Silver	No reaction	No fizzing, metal remains unchanged
Gold	No reaction	No fizzing, metal remains unchanged

3. Reactions with Oxygen

When heated in air:

Metal	Reaction with Oxygen	Product
Magnesium	Burns with a bright white flame	White ash — magnesium oxide (MgO)
Iron	Glows and produces sparks (especially iron wool)	Black iron oxide (Fe₃O₄)
Copper	Surface slowly turns black	Black copper oxide (CuO)
Gold	No reaction	No change

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The Role of Carbon and Hydrogen

Carbon and hydrogen are placed in the reactivity series as reference points because their positions determine:

1. Carbon's position — metals above carbon in the reactivity series cannot be extracted by reduction with carbon and must be extracted by electrolysis. Metals below carbon can be extracted by heating their ores with carbon (reduction with carbon).

2. Hydrogen's position — metals above hydrogen will react with dilute acids to produce hydrogen gas. Metals below hydrogen will not react with dilute acids.

Position	Extraction Method	Acid Reaction
Above carbon (K, Na, Ca, Mg, Al)	Electrolysis	React with water and/or acids
Between carbon and hydrogen (Zn, Fe)	Reduction with carbon	React with acids but not water
Below hydrogen (Cu, Ag, Au, Pt)	Reduction with carbon or found native	Do not react with dilute acids

Exam Tip: The positions of carbon and hydrogen in the reactivity series are crucial for understanding extraction methods and acid reactions. Many exam questions ask you to use these reference points to explain or predict outcomes.

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Aluminium: A Special Case

Aluminium appears to be unreactive because it has a very thin but tough layer of aluminium oxide on its surface. This oxide layer forms instantly when aluminium is exposed to air and protects the metal from further reaction.

However, aluminium is actually quite reactive — it sits above zinc in the reactivity series. When the oxide layer is removed (for example, by scratching the surface or using mercury), aluminium reacts vigorously.

This is why:

• Aluminium does not appear to react with cold water, even though its position suggests it should.
• Aluminium is extracted by electrolysis (not reduction with carbon), confirming its true position above carbon.

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Explaining Reactivity in Terms of Electron Loss

The reactivity of a metal depends on how easily it loses its outer electrons to form a positive ion:

• Metals that lose electrons easily are more reactive (e.g. potassium).
• Metals that hold onto their electrons tightly are less reactive (e.g. gold).

The ease of electron loss depends on:

1. Number of electron shells (more shells = outer electrons further from nucleus)
2. Shielding by inner electron shells
3. Nuclear charge (number of protons)

Exam Tip: When explaining why one metal is more reactive than another, always refer to the ease of losing outer electrons. For example: "Potassium is more reactive than sodium because potassium has more electron shells, so the outer electron is further from the nucleus, experiences more shielding, and is lost more easily."

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Testing for Hydrogen Gas

In reactions with water or dilute acid, hydrogen gas is produced. To test for hydrogen:

1. Collect the gas (e.g. using an inverted test tube).
2. Bring a burning splint to the mouth of the test tube.
3. If hydrogen is present, it burns with a squeaky pop.

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Summary