Activity Series of Metals: Predicting Single Displacement Reactions

What the Activity Series Is For

Single displacement reactions (A + BC → AC + B) are controlled by how easily one metal can push another metal out of a compound. The more readily a metal loses its electrons, the more "reactive" it is, and the better it is at kicking a less reactive metal out of solution.

The activity series is a ranked list of metals from most reactive to least reactive. It lets you predict, without looking up any thermodynamic data, whether a single displacement reaction will occur.

The rule is simple: a metal higher on the activity series will displace a metal lower on the series from its compound. A metal lower on the series will not react with the compound of a metal higher on the series.

The List (Most to Least Reactive)

Standard intro chemistry uses this ordered series, from most reactive to least reactive. Non-metal H₂ is included because its placement tells you which metals react with acids.

| Rank | Metal | Notes | |---|---|---| | 1 | Lithium (Li) | | | 2 | Potassium (K) | | | 3 | Barium (Ba) | | | 4 | Calcium (Ca) | | | 5 | Sodium (Na) | All above react with cold water | | 6 | Magnesium (Mg) | Reacts with steam | | 7 | Aluminum (Al) | Reacts with steam/acids; oxide layer protects it | | 8 | Zinc (Zn) | Reacts with acids | | 9 | Chromium (Cr) | | | 10 | Iron (Fe) | Reacts with acids | | 11 | Nickel (Ni) | | | 12 | Tin (Sn) | | | 13 | Lead (Pb) | Reacts slowly with acids | | — | Hydrogen (H₂) | Dividing line — metals above displace H⁺ from acids | | 14 | Copper (Cu) | Does not react with most dilute acids | | 15 | Mercury (Hg) | | | 16 | Silver (Ag) | | | 17 | Platinum (Pt) | | | 18 | Gold (Au) | Least reactive common metal |

Slight ordering variations exist between textbooks — especially for the middle metals — but the broad structure is stable. The extremes (Li/K/Na at the top, Au/Pt at the bottom) are universally agreed.

A Mnemonic for the Core List

One common mnemonic for the order:

"Please Stop Calling Me A Zebra, I Like Her Caged Safely Away"

• Potassium (note: Li is technically above K but most mnemonics start here)
• Sodium
• Calcium
• Magnesium
• Aluminum
• Zinc
• Iron
• Lead
• Hydrogen
• Copper
• Silver
• Aurum (gold)

Variations exist. Pick one you like and practice it; the specific letters matter less than locking the order into memory.

Where the Dividing Lines Matter

The series has a few natural thresholds:

Reaction with cold water

Metals at the top of the series — Li, K, Ba, Ca, Na — react vigorously with cold water, producing hydrogen gas and the metal hydroxide:

2 Na(s) + 2 H₂O(l) → 2 NaOH(aq) + H₂(g)

The reaction is exothermic and often dramatic; potassium ignites the released hydrogen as the reaction proceeds.

Reaction with steam or hot water

Magnesium reacts slowly with cold water but quickly with steam, producing magnesium oxide and hydrogen:

Mg(s) + H₂O(g) → MgO(s) + H₂(g)

Reaction with dilute acids

Metals above hydrogen in the series — everything from Li through Pb — react with dilute non-oxidizing acids (like HCl and dilute H₂SO₄) to produce hydrogen gas and a salt:

Zn(s) + 2 HCl(aq) → ZnCl₂(aq) + H₂(g)

Metals below hydrogen — Cu, Hg, Ag, Pt, Au — do not react with typical dilute acids. This is why copper pans do not corrode in vinegar and why gold can be buried for centuries and emerge shiny.

Reaction with more active metal ions in solution

A metal higher on the series will displace a metal lower on the series from an aqueous solution of its salt:

Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)

Zinc is higher on the series, so it pushes copper out of solution. Pure copper metal is deposited and the solution (originally blue from Cu²⁺) fades as zinc dissolves.

The reverse — putting copper metal into zinc sulfate solution — produces no reaction.

Predicting a Reaction: A Worked Example

Problem: Will iron react with a solution of silver nitrate?

1. Identify the reaction: Fe(s) + AgNO₃(aq) → ?
2. The candidate single displacement is iron displacing silver: Fe(s) + AgNO₃(aq) → Fe(NO₃)ₓ(aq) + Ag(s).
3. Check the activity series: iron is above silver. Iron is more reactive.
4. Yes, the reaction will proceed.

Balanced equation (with Fe²⁺ as the product ion):

Fe(s) + 2 AgNO₃(aq) → Fe(NO₃)₂(aq) + 2 Ag(s)

Silver metal will deposit on the iron, and iron will slowly dissolve into solution.

Problem: Will copper react with a solution of zinc sulfate?

1. Reaction: Cu(s) + ZnSO₄(aq) → ?
2. Candidate: Cu(s) + ZnSO₄(aq) → CuSO₄(aq) + Zn(s).
3. Check: copper is below zinc on the series. Copper is less reactive.
4. No reaction occurs.

A Brief Note on Halogens

Non-metals have their own "reactivity series" of sorts. For halogens, the order is:

F₂ > Cl₂ > Br₂ > I₂

A halogen higher in the list displaces one lower from its salt:

Cl₂(g) + 2 NaBr(aq) → 2 NaCl(aq) + Br₂(aq)

This is a non-metal analog of the metal activity series and shows up in the same way when you classify reactions.

Why the Rankings Exist

The activity series is a qualitative summary of standard reduction potentials — quantitative voltages measured for each metal's tendency to gain or lose electrons. The more negative the reduction potential, the more reactive the metal (the more eager it is to give up its electrons). If you move on to electrochemistry, you will see the activity series replaced by a proper table of reduction potentials, but for predicting single displacement reactions at the intro level, the ranked list in this article is all you need.

What to Memorize

At minimum, memorize:

1. The top five (Li, K, Ba, Ca, Na) — the metals that react with cold water.
2. Hydrogen's position — separating metals that react with dilute acids from those that do not.
3. The bottom three or four (Cu, Hg, Ag, Au) — the metals that resist corrosion and acid attack.
4. A few middle markers (Mg, Al, Zn, Fe) — the ones most commonly used in lab problems.

With those anchors, you can predict almost every single displacement reaction you will see in intro chemistry.