Atomic StructureTopic Summary
Topic Summary: Group 7 Halogens
Part of Group 7: Halogens — GCSE Chemistry
This topic summary covers Topic Summary: Group 7 Halogens within Group 7: Halogens for GCSE Chemistry. Revise Group 7: Halogens in Atomic Structure for GCSE Chemistry with 20 exam-style questions and 20 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 12 of 12 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 12 of 12
Practice
20 questions
Recall
20 flashcards
Topic Summary: Group 7 Halogens
Key Terms
- Halogen: Group 7, 7 outer electrons, form −1 ions
- Diatomic: Exist as pairs (F₂, Cl₂, Br₂, I₂)
- Halide ion: Cl⁻, Br⁻, I⁻
- Displacement: More reactive halogen replaces less reactive
- Reactivity trend: Decreases down Group 7
Must-Know Facts
- F₂: pale yellow gas; Cl₂: green gas; Br₂: orange-brown liquid; I₂: grey-purple solid
- Reactivity decreases going down Group 7
- Smaller atom = outer shell closer to nucleus = stronger pull on electrons
- More reactive halogen displaces less reactive halide
- Cl₂ + 2KBr → 2KCl + Br₂ (solution turns orange-brown)
- Opposite trend to Group 1!