Grade 9 → Metals and Nonmetals ↓
Reactivity Series of Metals
The reactivity series of metals, sometimes called the activity series, is a list of metals ranked in order of decreasing reactivity to displace other metals from compounds or to displace hydrogen from acids. This concept is important in the study of chemistry because it helps explain the behavior in chemical reactions involving metals and guides us in making predictions about such reactions.
Understanding reactivity
Reactivity in the context of metals refers to how strongly the metal will react with other substances such as water, acids, and other metal compounds. A more reactive metal will displace a less reactive metal from its compounds in a chemical reaction. For example, if we consider two metals, A and B, and A is more reactive than B, then A can displace B from a compound, but B cannot displace A
A + BC → AC + B (if A is more reactive than B)
A + BC → AC + B (if A is more reactive than B)
If A is not more reactive than B, then the reaction does not occur as written.
Reactivity series
The general sequence of the reactivity series is as follows:
- Potassium (K)
- Sodium (Na)
- Calcium (Ca)
- Magnesium (Mg)
- Aluminum (Al)
- Zinc (Zn)
- Iron (Fe)
- Lead (Pb)
- Hydrogen (H)
- Copper (Cu)
- Silver (Ag)
- Gold (Australia)
Examples and applications
Let us discuss some important reactions to understand the application of reactivity series.
Displacement reactions
When a more reactive metal displaces a less reactive metal from its compound, it is called a displacement reaction. Here is an example:
Zn + CuSO₄ → ZnSO₄ + Cu
Zn + CuSO₄ → ZnSO₄ + Cu
In this reaction, zinc displaces copper from copper sulfate to form zinc sulfate and copper metal. This happens because zinc is more reactive than copper.
Reaction with water
Metals can also react with water to form metal hydroxides and hydrogen gas. Highly reactive metals such as potassium, sodium, and calcium react quickly with cold water, while metals such as iron take longer:
2Na + 2H₂O → 2NaOH + H₂ (Sodium with water)
2Na + 2H₂O → 2NaOH + H₂ (Sodium with water)
In this example, sodium reacts vigorously with water to form sodium hydroxide and hydrogen gas.
Reaction with acids
Metals above hydrogen in the reactivity series can displace hydrogen from dilute hydrochloric or sulfuric acid. For example:
Mg + 2HCl → MgCl₂ + H₂
Mg + 2HCl → MgCl₂ + H₂
Magnesium is above hydrogen in the series, so it reacts with hydrochloric acid to form magnesium chloride and hydrogen gas. Metals below hydrogen (e.g., copper) do not react with hydrochloric acid to release hydrogen gas.
Why is the reactivity series important?
The reactivity series is important for a variety of applications, such as:
- To determine the feasibility of extracting metals from ores. Metals ranked higher in the series react more readily.
- Predicting the outcome of displacement reactions. This helps chemists decide which metals can be used to extract other metals or make certain compounds.
- Understanding corrosion and deciding which metals are best for construction based on their tendency to oxidize or rust.
- Selection of materials for batteries, where the reactivity of the metals determines the voltage output based on displacement reactions.
Summary
Understanding the reactivity series is fundamental in chemistry because it helps predict how metals will behave. By ranking metals from the most reactive (such as potassium) to the least reactive (such as gold), we gain information about how they will interact with water, acids, and other metals. Such knowledge supports applications in industries ranging from metal extraction and corrosion protection to energy storage, helping to ensure efficient and safe operations.
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