TheIB Chemistry | Year 2 (Senior) · Electron Sharing Reactions: Radicals · part 1/5
Radicals & Homolytic Fission Explained
IB Chemistry Reactivity 3.3, electron sharing reactions: radicals and homolytic fission (part 1 of 5, for SL and HL). What a radical is, how homolytic fission makes two radicals, and why the reaction of a halogen needs UV light. Includes a six mark exam-style question solved step by step.
In this lesson
- 0:00 Intro
- 0:14 Exam question
- 0:35 Warm-up
- 1:07 What a radical is
- 2:25 Homolytic fission
- 3:27 UV light and initiation
- 4:20 Practice: write the equation
- 5:30 What earns the mark
- 6:09 Exam question solved
- 7:01 Recap
Answers to the practice questions at the end of the video
- CH₃ has 9 electrons and NO has 15: odd numbers, so each has an unpaired electron [1 each]. CH₄ has 10 and N₂ has 14, all paired.
- I₂ → 2I•, with UV light (or heat) above the arrow [1].
- Without UV light there is not enough energy to break the Cl–Cl bond [1], so no chlorine radicals form and the reaction cannot start [1].
Questions are original, in the style of the exam; marks are estimates.
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