Reactivity of Metals

Section 1 of 6The reactivity series

Order of metals

• Order of metals From most to least reactive: potassium, sodium, calcium, magnesium, aluminium, zinc, iron, hydrogen (for comparison), copper.

What it tells you

• What it tells you The higher a metal is, the more readily it forms positive ions and the more vigorously it reacts.
• Evidence for the order comes from observing reactions with water, acid and salt solutions.

Hydrogen's place

• Hydrogen's place Only metals above hydrogen in the series react with dilute acids to release hydrogen gas.

Section 2 of 6Reactions with water and acid

Metal	With cold water	With dilute acid
Potassium	Violent	Violent, explosive
Sodium	Fast reaction	Violent, explosive
Calcium	Steady fizzing	Vigorous
Magnesium	Very slow	Vigorous fizzing
Zinc	Very slow	Moderate fizzing
Iron	Very slow	Slow fizzing
Copper	No reaction	No reaction

Section 3 of 6General equations

Metal reactions

Metal + water

• Metal + water Forms a metal hydroxide and hydrogen: Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g).

Metal + acid

• Metal + acid Forms a salt and hydrogen: Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g).
• Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g).

Metal + salt solution

• Metal + salt solution A more reactive metal displaces a less reactive one: Mg(s) + CuSO₄(aq) → MgSO₄(aq) + Cu(s).

Section 4 of 6Using displacement to rank metals

1

Place each metal in a solution of a salt of a different metal.

2

Look for signs of reaction: a new coloured coating, a colour change in the solution or a temperature rise.

3

If the added metal is more reactive it displaces the other, so the solid coats the surface and the solution fades from its original colour.

4

If no change occurs, the added metal is less reactive than the metal in the salt.

5

Combine many results to produce the order of reactivity.

Section 5 of 6Key terms

Term	Meaning
Reactivity series	A list of metals in order of how readily they react.
Displacement	A reaction in which a more reactive element takes the place of a less reactive one in a compound.
Metal hydroxide	The compound formed, with hydrogen, when a reactive metal reacts with water.
Vigorous	Fast, with lots of fizzing or heat.
Salt	A compound formed when a metal replaces the hydrogen of an acid.

Section 6 of 6Exam technique

1

Saying copper reacts slowly with acid; it is below hydrogen so it does not react at all.

2

Forgetting to balance equations such as Mg + 2HCl, where two HCl are needed.

3

Claiming a less reactive metal displaces a more reactive one; displacement only works the other way.

4

Writing that metals react with water to form oxides; with cold water the products are hydroxides and hydrogen.