CHEMISTRY · Stage 8 · Chapter 9: Chemical Reactions 2

Chemistry 9.6 Metals and oxygen — Metal Oxide Formation and Reactivity

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Lesson summary

9.6 Metals and oxygen — Metal Oxide Formation and Reactivity — Alhussan International Academy — Chemistry (Stages 7–9) notes: Define reactivity, describe how metals react with oxygen to form oxides and rank metals by the vigour of the reaction.General pattern — metal + oxygen → m…

Corrosion without heating
Metal properties
Observation
Surface atoms
Calcium and potassium
Heating magnesium ribbon

Part 1 of 6Metals and oxygen

General pattern — metal + oxygen → metal oxide, which is an oxidation reaction.
Magnesium — it burns vigorously with a bright white flame to make white magnesium oxide: magnesium + oxygen → magnesium oxide.
- Flares contain magnesium for the bright white light, with strontium nitrate to make a red flame.
Corrosion without heating — in air, over time, surface atoms of magnesium react with oxygen to make a thin layer of magnesium oxide.
Metal properties — metals have similar physical properties (shiny, conduct heat and electricity) and patterns in their chemical properties too.

Part 2 of 6Reactivity

Reactivity the tendency of a substance to take part in chemical reactions.
Observationthe more reactive a metal is, the more vigorously it reacts.
Surface atomsonly the surface atoms of a metal react with oxygen, forming an oxide layer.

Part 3 of 6Reactions of different metals with oxygen

Metal	Reaction with oxygen	Product
Sodium	Burns very vigorously; surface reacts quickly without heating	Sodium oxide and sodium peroxide
Magnesium	Burns vigorously with a bright white flame; surface reacts slowly without heating	Magnesium oxide
Zinc	Powder burns vigorously with a greenish flame; bigger pieces do not burn easily	Zinc oxide
Iron	Powder burns vigorously; bigger pieces do not burn easily	Iron oxide
Copper	Does not burn; surface turns black when heated	Copper oxide
Gold	No reaction	None

Order — the metals get less reactive from sodium to gold, and their reactivity decreases down the table.
Sodium — when it burns there is a mixture of products, sodium oxide (Na₂O) and sodium peroxide (Na₂O₂).
- A freshly cut surface reacts with oxygen at once, making white sodium oxide.
Calcium and potassium — potassium tarnishes within seconds and burns fiercely, and calcium burns with a red flame to make calcium oxide.
Copper — word equation: copper + oxygen → copper oxide.
Gold — its surface atoms do not react with oxygen, so it stays shiny and is used for connectors in audio equipment.

Part 4 of 6Mass change

1Heating magnesium ribbon1 point

— in a covered crucible, the mass of the solid increases because oxygen from the air becomes part of the oxide.

The lid is raised briefly to let air in without letting smoke escape.

2Conservation of mass

— mass of metal + mass of oxygen = mass of oxide.

3Properties of oxides1 point

— metal oxides are usually solids with high melting points.

Oxides of soluble metals such as sodium, potassium and calcium dissolve in water to form alkaline solutions, but many others are insoluble bases.

4Exothermic

— burning reactions of metals are exothermic, shown by the heat and light produced.

Part 5 of 6Explaining reactivity

Electrons — reactive metals lose their outer electrons easily to become positive ions.
- Potassium has one outer electron far from the nucleus, so it is lost with very little energy.
- Magnesium has two outer electrons, and copper holds its electrons more tightly.
Position in series — metals higher in the reactivity series combine with oxygen more readily.

Part 6 of 6Oxide layers and rusting

1Aluminium

— its oxide layer is hard, unreactive and sticks firmly, which protects the metal underneath.

2Iron1 point

— iron oxide (rust) is flaky and falls off, exposing new metal that then rusts further.

Rusting needs oxygen and water and is speeded up by salt.

3Comparing metals in a practical2 points

— use the same mass of each metal in the same form and heat in the same way.

Record the time to start burning, flame colour and the appearance of the product in a table.
Do not look directly at burning magnesium, and use tongs and a heat-resistant mat.

Last updated: 13 October 2026