To order metals from displacement results, find which metals push others out of solution. A metal that displaces another is more reactive than that metal. Count the displacements and the order appears.
This skill opens metals and reactivity. Extraction, corrosion and protection questions later all lean on the order you build here.
What is a displacement reaction?
A displacement reaction happens when a more reactive metal takes the place of a less reactive metal in a compound. Zinc in copper(II) sulfate solution is the standard case: Zn + CuSO₄ → ZnSO₄ + Cu.
In ionic form, Zn + Cu²⁺ → Zn²⁺ + Cu. Zinc atoms give up electrons to become ions, and copper ions take them and become copper atoms. The metal that loses electrons more easily is the more reactive one.
So the question to ask of any result is: did the added metal change, and which way did the change go?
How to build an order from a table
- List every test as “metal added, solution used, result”.
- Mark each reaction as a displacement. The added metal is higher than the metal in the solution.
- Mark each “no reaction”. The added metal is lower than, or not above, the metal in the solution.
- Count the displacements each metal made. The more it made, the higher it sits.
- Write the order from most reactive to least, then check every single result against it.
Worked example
These results use invented metals W, X, Y and Z and are for practice only. Each metal was added to a solution of the sulfate of each of the others.
| Metal added | W sulfate | X sulfate | Y sulfate | Z sulfate |
|---|---|---|---|---|
| W | (not tested) | reaction | reaction | reaction |
| X | no reaction | (not tested) | reaction | reaction |
| Y | no reaction | no reaction | (not tested) | reaction |
| Z | no reaction | no reaction | no reaction | (not tested) |
Step 1, count displacements: W made 3, X made 2, Y made 1, Z made 0.
Step 2, order: W > X > Y > Z, from most to least reactive.
Step 3, check: Y reacted with Z sulfate, so Y is above Z. X did not react with W sulfate, so X is not above W. Every cell agrees.
Answer: W, X, Y, Z. W is the most reactive and Z the least.
The mistake to watch for
A common slip is to read the table backwards and treat the metal in the solution as the reactive one.
Mistaken reading: “W sulfate reacted, so W is the least reactive.”
The student linked the word “reaction” to the solution, not to the solid metal added.
The correction is to name the solid first. Ask “which metal was added, and did it get used up?” The added metal is the one that changes, so it is the one that is higher in the order. Underline the metal added in each row before you write any conclusion.
Check yourself
Try these on paper first, then open each answer.
1. Copper is added to silver nitrate solution and a grey-white deposit forms. Which metal is more reactive? Write the balanced equation.
Show answer
Copper displaced silver, so copper is more reactive than silver. Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag. Check the atoms: Cu 1 each side, Ag 2 each side, NO₃ 2 each side.
2. Iron is added to magnesium sulfate solution. What do you expect, and why?
Show answer
No reaction. Magnesium is more reactive than iron, so iron cannot push magnesium out of its compound.
3. Invented metals P, Q and R: P displaces Q from Q sulfate, and Q displaces R from R sulfate. Put them in order.
Show answer
P beats Q, and Q beats R, so P > Q > R. P should also displace R, which you would confirm with one more test.
Where this leads next
Once you can rank metals from evidence, move on to relating extraction to reactivity, then test yourself with the metals and reactivity practice set. The equation balance reasoning trainer helps with the equations above, and the mole and equation-ratio tutor handles the amounts.
Some students rank the metals correctly but write the conclusion the wrong way round under exam pressure. That is a pattern our teachers look for in online one-to-one Chemistry tuition.