What does Edexcel GCSE Chemistry Topic 6 cover?

Topic 6 covers the three groups studied in detail: Group 1 the alkali metals (properties, reactions with water and oxygen, and increasing reactivity down the group), Group 7 the halogens (properties, trends, forming ions and compounds, decreasing reactivity, and displacement reactions), and Group 0 the noble gases (inertness from full outer shells, trends and uses).

Why does Group 1 reactivity increase down the group but Group 7 reactivity decrease?

Group 1 metals react by losing their single outer electron; down the group this electron is further from the nucleus and lost more easily, so reactivity increases. Group 7 non-metals react by gaining an electron; down the group the outer shell is further from the nucleus, so an electron is gained less easily, and reactivity decreases.

What is a halogen displacement reaction?

A more reactive halogen displaces a less reactive halogen from a solution of its salt. For example, chlorine displaces bromine from potassium bromide, turning the solution orange, because chlorine is more reactive. The ionic equation is chlorine plus bromide ions giving chloride ions plus bromine.

Why are the noble gases unreactive?

The Group 0 noble gases have a full outer shell of electrons, so they have no tendency to gain, lose or share electrons and are very unreactive. They exist as single atoms, and their inertness makes them useful in balloons, inert atmospheres and lighting.

What is the most common mistake in Topic 6?

Common mistakes are getting the reactivity trends the wrong way round, explaining the Group 1 or Group 7 trend by the number of outer electrons rather than the distance of the outer shell from the nucleus, predicting a less reactive halogen displacing a more reactive one, and saying the noble gases gain or lose electrons.

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Edexcel GCSE Chemistry Topic 6 Groups in the periodic table: a complete overview

A deep-dive Edexcel GCSE Chemistry guide to Topic 6 Groups in the periodic table. Covers the Group 1 alkali metals and their increasing reactivity, the Group 7 halogens and their decreasing reactivity and displacement reactions, the Group 0 noble gases and their inertness, and how each trend is explained by electronic structure.

Generated by Claude Opus 4.814 min readTopic 6Updated 2026-06-02

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What Topic 6 actually demands
Group 1 the alkali metals
Group 7 the halogens
Group 0 the noble gases
How Topic 6 is examined
Check your knowledge

What Topic 6 actually demands

Groups in the periodic table is a Paper 2 topic that rewards clear, consistent explanation of reactivity trends in terms of electronic structure. Edexcel tests the properties and reactions of Groups 1, 7 and 0, the opposite reactivity trends of the metals and non-metals, and halogen displacement with ionic equations.

This guide walks through the topic in specification order, then sets out the exam patterns Edexcel repeats. Each dot point has a matching page with practice questions; this overview ties them together.

Group 1 the alkali metals

The alkali metals are soft, low-density, low-melting metals with one outer electron. They react with water to give a hydroxide and hydrogen (an alkaline solution) and with oxygen to form oxides. Reactivity increases down the group, because the outer electron is further from the nucleus and lost more easily. Their shared outer-electron count gives them similar chemical properties.

Group 7 the halogens

The halogens are reactive non-metals existing as diatomic molecules with seven outer electrons. Down the group they get darker and their melting and boiling points increase (chlorine gas, bromine liquid, iodine solid). They form $1-$ ions with metals and covalent molecules with non-metals. Reactivity decreases down the group, because an electron is gained less easily as the outer shell moves further from the nucleus. A more reactive halogen displaces a less reactive one from its salt.

Group 0 the noble gases

The noble gases are inert because they have a full outer shell, so they do not gain, lose or share electrons. They are monatomic colourless gases. Down the group, boiling point and density increase. Their inertness makes them useful in balloons (helium), inert atmospheres (argon) and lighting (neon).

How Topic 6 is examined

A typical Edexcel profile for this topic:

Group 1 reactions and trend. Observations with water and the increasing-reactivity explanation.
Group 7 trends and displacement. The decreasing-reactivity explanation and ionic equations.
Group 0 inertness and trends. Explaining unreactivity and interpolating physical-property data.
Cross-group reasoning. Linking position and outer electrons to properties.

Check your knowledge

A mix of recall and application questions covering Topic 6. Attempt them under timed conditions, then check against the solutions.

State the number of outer electrons in a Group 1, a Group 7 and a Group 0 atom. (3 marks)
Write the equation for sodium reacting with water. (2 marks)
Explain why reactivity increases down Group 1. (2 marks)
State the trend in melting point down Group 7. (1 mark)
Write the ionic equation for chlorine displacing bromine from potassium bromide. (2 marks)
Explain why reactivity decreases down Group 7. (2 marks)
Explain why the noble gases are unreactive. (1 mark)
Give one use of helium and the property that makes it suitable. (2 marks)

Solutions

Q1: Group 1 has one outer electron; Group 7 has seven; Group 0 has a full outer shell (two for helium, eight for the others).
Q2: $2Na + 2H_2O \rightarrow 2NaOH + H_2$ .
Q3: The single outer electron is further from the nucleus down the group, so it is less strongly attracted and lost more easily, making the metals more reactive.
Q4: The melting point increases down Group 7.
Q5: $Cl_2 + 2Br^- \rightarrow 2Cl^- + Br_2$ .
Q6: An electron is gained less easily down the group, because the outer shell is further from the nucleus and more shielded, so the attraction for the incoming electron is weaker.
Q7: They have a full outer shell, so they have no tendency to gain, lose or share electrons.
Q8: Helium is used in balloons or airships because it has a very low density and is non-flammable.

Sources & how we know this

Pearson Edexcel GCSE (9-1) Chemistry (1CH0) specification — Pearson Edexcel (2016)