How to explain the reactivity series with examples

The reactivity series is one of the highest-value pages you can memorise for SPM Chemistry, because a single ordered list quietly decides dozens of exam answers, how a metal reacts with water and acid, which metal displaces which, and how each metal is extracted. This guide explains what the series means and shows worked examples so you can use it, not just recite it. Keep the full reactivity series table beside you as you read.

The order you need to know

From most reactive to least reactive, the SPM series is:

Potassium (K) → Sodium (Na) → Calcium (Ca) → Magnesium (Mg) → Aluminium (Al) → [Carbon] → Zinc (Zn) → Iron (Fe) → Tin (Sn) → Lead (Pb) → [Hydrogen] → Copper (Cu) → Silver (Ag) → Gold (Au)

Carbon and hydrogen are non-metals, but they are slotted in as reference points because so many questions are decided by whether a metal sits above or below them. A common mnemonic is: Please Stop Calling Me A Zebra, I Take Long Hours Cutting Silver Gold, pick or invent one that sticks for you.

Why the series works

Reactivity here means how readily a metal loses electrons to form a positive ion. Metals at the top lose electrons very easily, so they react fast and are hard to extract from their compounds. Metals at the bottom hold their electrons tightly, react slowly or not at all, and can even be found as the pure metal in nature. Once you see the series as an “eagerness to become an ion” ladder, every example below falls into place.

Example 1: reaction with water

• Potassium, sodium, calcium react with cold water, giving a metal hydroxide and hydrogen gas. For example, sodium: 2Na + 2H₂O → 2NaOH + H₂. You can see this dramatic behaviour in Group 1 metals reacting with water.
• Magnesium, zinc, iron react only with steam, not cold water, giving the metal oxide and hydrogen.
• Copper, silver, gold do not react with water at all.

The pattern: the higher the metal, the milder the conditions it will react under.

Example 2: reaction with dilute acid

The hydrogen reference point rules this one. A metal above hydrogen displaces hydrogen from dilute acid, so it fizzes and releases hydrogen gas:

Mg + 2HCl → MgCl₂ + H₂

Magnesium, zinc and iron all fizz with dilute acid, faster higher up the series. A metal below hydrogen (copper, silver, gold) does not react with dilute acid, which is exactly why copper coins survive. So if a question asks whether copper reacts with dilute hydrochloric acid, the answer is a confident “no, copper is below hydrogen”.

Example 3: displacement

A more reactive metal displaces a less reactive metal from its salt solution. Because magnesium is above copper:

Mg + CuSO₄ → MgSO₄ + Cu

The blue solution fades and reddish-brown copper deposits. Reverse the metals and nothing happens, because copper cannot push out the more reactive magnesium. The higher the displacing metal sits, the more vigorous (and more exothermic) the reaction.

Example 4: extracting metals

The carbon reference point decides extraction method:

• Metals above carbon (K, Na, Ca, Mg, Al) are too reactive for carbon to remove the oxygen, so they are extracted by electrolysis.
• Metals below carbon (Zn, Fe, Sn, Pb) can be extracted by heating their oxide with carbon, because carbon is more reactive and reduces the oxide. For iron: 2Fe₂O₃ + 3C → 4Fe + 3CO₂. See reduction of a metal oxide by carbon for the full idea.
• Metals very low (copper, silver, gold) are so unreactive they need little more than heating, or are found native.

So the higher a metal is, the more energy (and electricity) its extraction demands, which is why aluminium is more expensive to win than iron.

A worked deduction

“Does zinc react with dilute sulfuric acid, and can zinc be extracted by carbon?”

• Zinc is above hydrogen, so yes, it fizzes: Zn + H₂SO₄ → ZnSO₄ + H₂.
• Zinc is below carbon, so yes, it can be extracted by heating zinc oxide with carbon.

Two answers, both read straight off the ladder. That is the power of the series: it turns guesswork into one-line deductions.

Common mistakes to avoid

• Calling aluminium unreactive because it seems inert. It is actually high in the series; a tough oxide layer just protects the surface.
• Saying copper fizzes in acid. It sits below hydrogen, so it does not react.
• Getting displacement backwards, only a higher metal displaces a lower one.
• Trying to extract sodium or magnesium with carbon. They are above carbon and need electrolysis.

Learn it as a tool, not a chant

Do not just memorise the list; practise reading answers off it. Cover the table, pick a metal, and predict its reaction with water, with acid, and its extraction method, then check. After a dozen metals it becomes instinct, and a whole spread of Paper 1 and Paper 2 questions turns quick and confident.

If the series or its applications keep slipping, a teacher can fix it fast. Our online one-to-one lessons run in English from RM50 an hour, with a paid one-hour trial; see how it works if you would like it drilled against real SPM questions.