Metal Properties and Reactivity: Revision Notes

Condensed for the final weeks. For the full explanation, use the Metal Properties and Reactivity study guide, and test yourself with the practice questions.

Physical properties

Metals share good thermal and electrical conductivity, malleability (can be hammered into shape without shattering) and ductility (can be drawn into wires), plus generally high melting and boiling points. All of these come from the same cause: metallic bonding — a lattice of positive ions in a “sea” of delocalised electrons. The delocalised electrons carry charge (conductivity) and heat, while the ions can slide past one another without breaking the bonding (malleability, ductility).

The reactivity series — learn the order

K   Na   Ca   Mg   Al   (C)   Zn   Fe   (H)   Cu   Ag   Au
MOST reactive ------------------------------> LEAST reactive

Learn this order directly — potassium, sodium, calcium, magnesium, aluminium, (carbon), zinc, iron, (hydrogen), copper, silver, gold.

Carbon and hydrogen are inserted because they determine extraction method and acid reaction — neither is a metal, but both act as reference points against which the true metals are judged.

Reactions in one table

Metal	With cold water	With steam	With dilute acid
K, Na, Ca	Vigorous → hydroxide + H₂	—	Dangerously violent
Mg	Very slow	Rapid → oxide + H₂	Rapid
Zn, Fe	No	Slow → oxide + H₂	Moderate
Cu, Ag, Au	No	No	No reaction

metal + water  ->  metal hydroxide + hydrogen
metal + steam  ->  metal oxide     + hydrogen
metal + acid   ->  salt            + hydrogen

Metals below hydrogen (Cu, Ag, Au) do not react with dilute acid — the standard one-mark question.

Worked example. Magnesium ribbon reacts vigorously with dilute hydrochloric acid; iron filings react slowly with gentle fizzing; copper powder shows no reaction. Rank the three by reactivity, with reasoning.

More vigorous reaction with acid = more reactive metal.
Magnesium > Iron > Copper

Consistent with the reactivity series: Mg sits well above Fe, and Fe is
above hydrogen while Cu sits below it -- matching Cu's total lack of reaction.

Displacement

A more reactive metal displaces a less reactive one from its compound.

Zn + CuSO4  ->  ZnSO4 + Cu     (blue solution fades, brown deposit)
Cu + ZnSO4  ->  NO REACTION

These are redox: the more reactive metal is oxidised (loses electrons); the metal ion is reduced. The same idea underlies sacrificial protection below — a more reactive metal is deliberately sacrificed (oxidised) so a less reactive one is not.

Extraction — decided by reactivity

Position	Method	Examples
Above carbon	Electrolysis	K, Na, Ca, Mg, Al
Below carbon	Reduction with carbon	Zn, Fe, Pb
Very unreactive	Found native	Au, Ag

Aluminium needs electrolysis despite the cost because carbon cannot reduce it — electrolysis uses far more energy than heating with carbon, but it is the only option for a metal above carbon in the series.

Aluminium’s apparent unreactivity

Aluminium is high in the reactivity series, above zinc and iron, but seems unreactive in everyday life. The reason: a thin, impermeable layer of aluminium oxide forms immediately on the surface and seals the metal underneath from oxygen, water and acid. If scratched, the exposed aluminium instantly forms fresh oxide, so the protection re-forms itself.

Rusting

Both water and oxygen are required. Salt accelerates it; it is not a cause.

iron + oxygen + water  ->  hydrated iron(III) oxide

Prevention:

• Barrier — painting, greasing, plastic coating, tin plating.
• Sacrificial protection — attaching a more reactive metal (zinc, magnesium) which corrodes instead.
• Galvanising — zinc coating: barrier and sacrificial, which is why it is preferred.

Exam traps

• Water gives hydroxide; steam gives oxide. Different products.
• Salt does not cause rust — it speeds it up.
• Sacrificial metal must be more reactive than iron.
• A scratched tin can rusts faster than bare iron (tin is less reactive, so iron corrodes preferentially).
• Extraction method follows the metal’s position relative to carbon.
• Explaining malleability or conductivity without mentioning the delocalised electron sea — “metals are shiny” is not a mechanism.
• Ranking metals by acid reaction without linking the observation (vigour of fizzing) back to the reactivity series explicitly.

Self-test

1. Why is copper unreactive with dilute acid?
2. Give the products of magnesium with steam.
3. Will magnesium displace zinc from zinc sulfate? Explain.
4. Why is aluminium extracted by electrolysis rather than with carbon?
5. Why is galvanising better than tin plating?
6. Explain, in terms of structure and bonding, why metals conduct electricity.
7. Zinc granules react steadily with dilute hydrochloric acid; magnesium ribbon reacts violently; lead reacts extremely slowly. Rank the three by reactivity.

Answers: 1. It lies below hydrogen in the reactivity series, so it cannot displace hydrogen from the acid. 2. Magnesium oxide and hydrogen. 3. Yes — magnesium is more reactive than zinc, so it displaces zinc: Mg + ZnSO₄ → MgSO₄ + Zn. 4. Aluminium is above carbon in the reactivity series, so carbon cannot reduce its oxide; electrolysis is required. 5. Zinc is more reactive than iron, so it protects both as a barrier and sacrificially even when scratched; tin is less reactive, so a scratch causes the iron to corrode faster. 6. Metals have delocalised electrons in a “sea” around a lattice of positive ions; these electrons are free to move throughout the structure and carry charge, allowing conduction. 7. Magnesium (most vigorous) > Zinc (steady) > Lead (extremely slow) — matching their order in the reactivity series.