Syllabus Edition

First teaching 2023

First exams 2025

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Physical Properties of the Group 17 Elements (CIE A Level Chemistry)

Topic Questions

1a4 marks

The elements of Group 17 of the Periodic Table show trends in their properties.

i)
Complete Table 2.1, stating the colour of each element in its state at room temperature.
[2] 

Table 2.1

Halogen Boiling point / °C Colour
Chlorine -36  
Bromine  59  
Iodine  184   

ii)
Briefly explain why the boiling points of the halogens increase from chlorine to iodine.
[2]
1b1 mark

State the full electronic configuration for bromine.

1c3 marks

Explain why bromine is a liquid at room temperature, but fluorine and chlorine are gases.

1d3 marks

The bond enthalpy of the halogen molecules generally decreases down Group 17. Explain why the bond strength of fluorine is lower than that of chlorine. 

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2a3 marks

Chlorine is a greenish-yellow gas, bromine is a dark red liquid, and iodine is a dark grey solid.

State and explain the property which most directly causes these differences in volatility.

2b2 marks

Explain why Cl2 rather than Br2 would react more vigorously with a solution of I-.

2c2 marks

Astatine, At, is the rarest naturally occurring element in the Earth’s crust. Before it was discovered in 1940 scientists could only predict its existence and properties.

Suggest the basis for these predictions.

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3a4 marks

State and explain the trend in the boiling points of the halogens from fluorine to iodine.

trend 

explanation 

3b2 marks

The bond enthalpies of the halogens generally decrease down the group as shown in Table 3.1. 

Table 3.1 

Halogen Bond enthalpy (kJ mol–1)
F–F 159
Cl–Cl 242
Br–Br 193
I–I 151

State and explain the deviation in this trend.

deviation



explanation

3c2 marks

Chlorine is a strong oxidising agent.

Write the simplest ionic equation for the reaction between chlorine and aqueous sodium iodide. State what is observed when this reaction occurs.

equation


observation


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