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3.3.1—Radicals

Syllabus
First assessment 2025
Objective
3.3.1
Level
HL

Free Radicals

A radical is a highly reactive species containing an unpaired electron. Show the unpaired electron with a dot next to the atom that carries it.

Homolytic fission creates radicals because each covalent-bond fragment retains one bonding electron.

The dot in Cl· or CH₃· represents one unpaired electron, not a positive or negative charge. Radicals react readily because pairing that electron can form a bond; track the dot through every equation so electron and atom accounting remain explicit.

Recognizing Radical Notation

Assessment in practice

Representative question

Question 1

[Maximum number: 1]

Which radical is most likely to form during the breakdown of one covalent bond of dichlorofluoromethane, CHCl2 F\mathrm{CHCl}_{2} \mathrm{~F}, in the upper atmosphere?

A

⋅CHClF\cdot \mathrm{CHClF}

B

⋅CCl2 F\cdot \mathrm{CCl}_{2} \mathrm{~F}

C

⋅CHCl2\cdot \mathrm{CHCl}_{2}

D

⋅CHCl2 F\cdot \mathrm{CHCl}_{2} \mathrm{~F}

Radical Chain Summary

Retrieve the route: locate the unpaired electron, split the bond homolytically, initiate with UV or heat, propagate by single-electron steps and terminate by radical combination.

Every propagation step must regenerate a radical, and every radical symbol and single-electron movement must be shown where required.