Question
What is the reactivity series of metals? Explain how it predicts whether a displacement reaction will occur. Give three examples.
(CBSE 2023)
Solution — Step by Step
The reactivity series arranges metals in decreasing order of their chemical reactivity:
K > Na > Ca > Mg > Al > Zn > Fe > Ni > Sn > Pb > H > Cu > Hg > Ag > Au > Pt
(Most reactive at top, least reactive at bottom)
A more reactive metal can displace a less reactive metal from its salt solution. But not the other way around.
If Metal A is above Metal B in the reactivity series, then A can displace B from a solution of B’s salt.
If A is below B, no reaction occurs.
Iron (Fe) is above copper (Cu) in the series.
When an iron nail is dipped in blue copper sulphate solution, the solution turns green (FeSO) and a reddish-brown deposit of copper appears on the nail.
Zinc is above copper.
Copper is below zinc in the series.
This is the key prediction: less reactive metals cannot displace more reactive metals from their salt solutions.
Why This Works
Reactivity measures how easily a metal loses electrons (gets oxidised). A more reactive metal “wants” to lose electrons more than a less reactive one. In a displacement reaction, the more reactive metal gives up its electrons to the less reactive metal’s ions, forcing the less reactive metal out of solution and into solid form.
Think of it as a competition: the stronger “electron donor” (more reactive metal) pushes the weaker one out. Gold and platinum sit at the bottom — they’re so reluctant to lose electrons that almost nothing can displace them. That’s why they don’t corrode and are called “noble metals.”
Alternative Method — Using the mnemonic
To memorise the reactivity series, use: Please Stop Calling Me A Zebra, I Need Some Love Here Come Happy Singing Golden Parrots.
(K, Na, Ca, Mg, Al, Zn, Fe, Ni, Sn, Pb, H, Cu, Hg, Ag, Au, Pt)
Note that hydrogen (H) is included in the series. Metals above hydrogen react with dilute acids to produce hydrogen gas. Metals below hydrogen (Cu, Ag, Au, Pt) do NOT react with dilute HCl or HSO.
Common Mistake
Students often try to displace a metal higher in the series and expect a reaction. For instance, adding copper to iron sulphate solution and expecting a reaction — this won’t happen because copper is less reactive than iron. Always check: is the free metal ABOVE the metal in the salt solution? Only then will displacement occur.