Section 1 of 4Electrons and the Series
The reactivity series is an ordered list built from observations of how metals react with other substances.
Ordering
- Metals are placed in order of how readily they react with substances such as water and dilute acids.
Forming ions
- Metal atoms react by losing electrons to form positive ions, so the tendency to lose electrons measures reactivity.
Trend
- Reactivity decreases going down the series, so metals lower down form ions less easily.
Carbon and hydrogen
- Carbon and hydrogen are included because carbon is used to extract metals from their oxides by reduction.
Section 2 of 4Reactions With Water and Acids
Observing these reactions allows metals to be ranked in the series.
1
Potassium reacts violently with cold water, giving off hydrogen gas and forming an alkaline solution of potassium hydroxide.
2
Calcium fizzes steadily with cold water to form calcium hydroxide and hydrogen, while magnesium reacts very slowly with cold water.
3
Metals above hydrogen react with dilute acids to form a salt and hydrogen gas, such as iron forming iron(II) chloride with hydrochloric acid.
4
Copper, silver and gold lie below hydrogen and do not react with dilute acids.
| Metal | Reaction with cold water | Reaction with dilute acid |
|---|---|---|
| Potassium | Violent; hydroxide and hydrogen form | Very violent |
| Calcium | Fizzes; hydroxide and hydrogen form | Vigorous |
| Magnesium | Very slow in cold water | Vigorous |
| Iron | Very slow | Moderate |
| Copper | No reaction | No reaction |
Section 3 of 4Predicting Reactivity
Predicting Reactivity
Tendency
- The more reactive the metal, the more easily it loses electrons to form positive ions.
Exceptions
- Aluminium is high in the series but reacts slowly, because a protective oxide layer forms on its surface.
Patterns
- The series describes trends and patterns rather than absolute rules for every chemical situation.
Hydrogen
- Metals above hydrogen displace it from acids, while metals below hydrogen do not react with dilute acids.
Section 4 of 4Exam Checklist & Tips
3.2.1 – Key Points for the Exam
- Reactivity series A list of metals in order of how readily they lose electrons and react.
- Oxidation Loss of electrons by an atom, ion or molecule.
- Protective oxide layer A thin, unreactive layer of oxide that stops further reaction, as on the surface of aluminium.
- Dilute acid An acid solution in which a relatively small amount of acid is dissolved in water.
Common Mistakes
- Saying the most reactive metals are at the bottom of the series.
- Stating that aluminium does not react at all, rather than reacting slowly because of its oxide layer.
- Writing that metals form negative ions in their reactions with water or acids.
- Forgetting that copper does not react with dilute acids because it lies below hydrogen.