Reactivity Series and Metal ExtractionAQA GCSE Chemistry: Revision notes

When metals react with oxygen they form metal oxides. This is an example of oxidation and reduction:

• Oxidation = gain of oxygen
• Reduction = loss of oxygen

Metal + oxygen → metal oxide is an oxidation reaction for the metal, since the metal gains oxygen.

Metals can be arranged in order of reactivity by observing how vigorously they react with water and with dilute acids. The reactivity series (most to least reactive) includes:

potassium, sodium, lithium, calcium, magnesium, zinc, iron, (hydrogen), copper

Carbon is also included in the series (between aluminium and zinc in the full series) because it is used to extract metals.

A metal's reactivity with water or dilute acid depends on how easily it loses electrons to form a positive ion.

• More reactive metals lose electrons more easily, forming their positive ions more readily
• This is why potassium (which loses its single outer electron very easily) reacts far more violently than copper (which holds onto its electrons strongly)
• An order of reactivity can be deduced from experimental results — for example, comparing the rate of fizzing (hydrogen produced) when different metals are added to the same dilute acid

The reactivity series determines how a metal must be extracted from its compounds (ores):

• Metals less reactive than carbon can be extracted from their oxides by reduction with carbon (the carbon removes the oxygen)
• Metals more reactive than carbon (e.g. potassium, sodium, calcium, magnesium, aluminium) cannot be extracted this way and require electrolysis instead
• Very unreactive metals, such as gold, are found in the Earth as the metal itself (uncombined), so do not need to be chemically extracted at all

In metal extraction reactions, always identify which substance loses oxygen (reduced) and which gains oxygen (oxidised):

• e.g. iron(III) oxide + carbon → iron + carbon dioxide: the iron oxide is reduced (loses oxygen) and the carbon is oxidised (gains oxygen)

(HT only) A more modern definition uses electrons, remembered as OIL RIG:

• Oxidation Is Loss (of electrons)
• Reduction Is Gain (of electrons)

HT students should also be able to write ionic equations for displacement reactions (where a more reactive metal displaces a less reactive one from a compound) and identify which species are oxidised and which are reduced within them.