Overview of Reactivity Series
The Reactivity Series (or Activity Series) is a list of metals arranged in the order of their decreasing chemical reactivity. The most reactive metals are placed at the top, while the least reactive metals are at the bottom. This series is a crucial tool in chemistry for predicting how metals will interact with other substances, such as water, acids, and solutions of other metal salts.
The Series Order
A common mnemonic to remember the series is: “Please Stop Calling Me A Zebra, I Like Her Calling Me Smart Guy” (or similar variations).
The Order (Most to Least Reactive):
- Potassium (K)
- Sodium (Na)
- Calcium (Ca)
- Magnesium (Mg)
- Aluminium (Al)
- Zinc (Zn)
- Iron (Fe)
- Lead (Pb)
- Hydrogen (H) – included for comparison
- Copper (Cu)
- Mercury (Hg)
- Silver (Ag)
- Gold (Au)
Key Concepts
1. Displacement Reactions
A more reactive metal can displace a less reactive metal from its salt solution. For example, Iron is more reactive than Copper. Therefore, if you place an iron nail in copper sulphate solution, the iron displaces the copper.
Equation: Fe(s) + CuSO4(aq) -> FeSO4(aq) + Cu(s)
Conversely, Copper cannot displace Iron from Iron Sulphate because Copper is less reactive than Iron.
2. Reaction with Water and Acids
The position of a metal determines its reaction with water and acids:
- Top metals (K, Na, Ca): React vigorously with cold water.
- Middle metals (Mg, Al, Zn, Fe): React with steam or hot water; react with dilute acids to release Hydrogen gas.
- Bottom metals (Cu, Ag, Au): Do not react with water or dilute acids to release Hydrogen.
Summary Table
| Metal Category | Examples | Reactivity | Extraction Method |
|---|---|---|---|
| Top of Series | K, Na, Ca, Mg, Al | Very High | Electrolysis |
| Middle of Series | Zn, Fe, Pb | Moderate | Reduction with Carbon |
| Bottom of Series | Cu, Ag, Au | Low | Found in Native State |
Quick Revision Points
- Hydrogen is a non-metal but is included to show which metals can displace hydrogen from acids.
- Gold and Platinum are noble metals and are least reactive.
- Potassium and Sodium are stored in kerosene to prevent accidental reaction with air and moisture.
- Aluminium forms a protective oxide layer which prevents further corrosion, despite being highly reactive.
Extra Practice Questions
- Why does copper not liberate hydrogen from dilute acids?
- Arrange Zn, Fe, and Cu in increasing order of reactivity.
- What happens when a strip of Zinc is placed in Copper Sulphate solution? Write the equation.
- Which metal is used to galvanize iron to protect it from rusting? Why?
- Name one metal that can be found in nature in its free state.
