The activity series ranks elements by how readily they give up electrons in aqueous solution. You need it to predict single displacement reactions in Predicting Products, and you built a short version of it yourself by experiment in Building the Activity Series.
The rule it exists to support is one sentence: a more active element displaces a less active one from its compound. A less active element does nothing at all.
The metals, most active at the top
| Metal | Symbol | What it reacts with |
|---|---|---|
| Lithium | cold water, producing hydrogen and a hydroxide | |
| Potassium | cold water | |
| Barium | cold water | |
| Strontium | cold water | |
| Calcium | cold water | |
| Sodium | cold water | |
| Magnesium | hot water and steam; acids readily | |
| Aluminium | steam; acids | |
| Manganese | steam; acids | |
| Zinc | steam; acids | |
| Chromium | steam; acids | |
| Iron | steam; acids | |
| Cadmium | acids | |
| Cobalt | acids, slowly | |
| Nickel | acids, slowly | |
| Tin | acids, slowly | |
| Lead | acids, very slowly | |
| Hydrogen | the dividing line | |
| Copper | not water, not dilute acids | |
| Mercury | not water, not dilute acids | |
| Silver | not water, not dilute acids | |
| Platinum | essentially nothing | |
| Gold | essentially nothing |
Hydrogen is in the list even though it is not a metal, because its position is the most useful single fact on the page: a metal above hydrogen displaces hydrogen from an acid; a metal below it does not.
Copper in hydrochloric acid gives you copper sitting in hydrochloric acid. Not a slow reaction — no reaction.
The halogens, most active at the top
| Halogen | Symbol |
|---|---|
| Fluorine | |
| Chlorine | |
| Bromine | |
| Iodine |
Plain periodic-table order, and a halogen displaces any halide below it:
Bromine added to sodium chloride solution does nothing, because bromine is below chlorine. This is the halogen equivalent of the metals rule and it works the same way.
How to use it
- Write down which element is going in on its own, and which element is currently in the compound.
- Find both in the table.
- If the lone element is higher, the reaction happens — write the products and balance them.
- If it is lower, or the same element, the answer is no reaction, written out in those two words.
Two predictions, one of each kind
Zinc metal placed in copper(II) sulfate solution. Zinc is above copper, so zinc displaces it. The blue fades and the strip goes copper-coloured.
Copper metal placed in zinc sulfate solution. Copper is below zinc, so there is no reason for copper to hand over electrons. No reaction — and this is the more informative half of the pair, because a series that predicted both directions would predict nothing at all.
Three honest notes
Lists differ near the bottom. Copper, mercury, and silver are close enough together that different textbooks order them differently, and some series omit the rarer metals entirely. Where two neighbours are adjacent in the table, do not build an argument on which one is higher — use the data booklet you are given.
The order is about ions in water, not about drama. Lithium sits above potassium here, and yet potassium reacts far more violently with water than lithium does. There is no contradiction: the series ranks the tendency to form a hydrated ion in solution, and lithium’s very small ion is stabilised by water unusually well. What you see in a demonstration is dominated by how fast the reaction goes and how much heat is released, which is a different question.
The series says what can happen, not how fast. Aluminium sits high in the list and yet aluminium window frames survive rain for decades, because a tough oxide layer forms on the surface and protects the metal underneath. A prediction of “reaction” that produces nothing visible may be a prediction about rate rather than a wrong prediction — which is exactly the kind of distinction What Counts as Evidence is about.