The reactivity series: The non-metals hydrogen and carbon are often included in the reactivity series.

The idea

The reactivity series is usually a list of metals in order of how vigorously they react, but hydrogen and carbon are non-metals that are often placed within it as reference points. Hydrogen is shown as a non-metal against which metals can be compared: metals above hydrogen displace it from dilute acids, while metals below it generally do not. Carbon is shown as a non-metal that can reduce metal oxides when it is more reactive than the metal, which is how carbon is used in extracting some metals from their ores. For example, carbon reduces zinc oxide because carbon is above zinc, but carbon cannot reduce aluminium oxide because aluminium is above carbon. Including these non-metals lets chemists predict displacement and reduction behaviour, even though they are not metals.

What earns the marks

• Hydrogen and carbon are non-metals, not metals, yet they are often placed within the reactivity series as reference points.
• Hydrogen is used to judge whether a metal reacts with dilute acid: metals above hydrogen displace hydrogen from the acid, while metals below hydrogen generally do not.
• Carbon is used to judge whether a metal oxide can be reduced by carbon: carbon reduces the oxide if carbon is above the metal in the series.
• The position of a non-metal in the series is a comparison of reactivity, not a claim that it is a metal.
• A concrete example is that carbon reduces zinc oxide to zinc because carbon is above zinc, but carbon does not reduce aluminium oxide because aluminium is above carbon.
• Hydrogen and carbon are included so that displacement and reduction can be predicted using one ordered list.

Common mistakes and how to put them right

• Calling hydrogen and carbon metals because they appear in the reactivity series.

  Put it right: They are non-metals included as reference points.

• Thinking any metal below hydrogen will fizz in dilute acid.

  Put it right: Metals below hydrogen generally do not displace hydrogen from dilute acid.

• Assuming carbon can reduce every metal oxide.

  Put it right: Carbon only reduces oxides of metals below carbon in the series, such as zinc oxide, not aluminium oxide.

Exam tips

• State clearly that hydrogen and carbon are non-metals when you refer to their position in the series.
• Use the phrases above hydrogen and below hydrogen to explain acid reactions, and above the metal to explain reduction by carbon.
• Give one named example, such as carbon reducing zinc oxide, to show the predictive use of the series.