Group 7 Halogens – Notes + Past Paper Questions (IGCSE 0620 | O Level 5070 | A Level 9701)
100% Syllabus | Displacement Reactions | Trends | Colours | Equations | Updated 2025–2027
60-Second Mood Booster – Refresh Before Halogens!
Group 7 Halogens: F₂, Cl₂, Br₂, I₂, At
All have 7 valence electrons → highly reactive non-metals → exist as diatomic molecules
All have 7 valence electrons → highly reactive non-metals → exist as diatomic molecules
Appearance & Physical State at Room Temp
| Halogen | Colour | State |
|---|---|---|
| Fluorine (F₂) | Pale yellow | Gas |
| Chlorine (Cl₂) | Greenish-yellow | Gas |
| Bromine (Br₂) | Red-brown | Liquid |
| Iodine (I₂) | Dark grey (solid) → Purple vapour | Solid |
Trends Down Group 7 (6-Mark Guaranteed)
| Property | Trend Down Group | Reason |
|---|---|---|
| Boiling/Melting point | Increases | Larger molecule → stronger van der Waals forces |
| Reactivity | Decreases (F > Cl > Br > I) | Outer shell further from nucleus → harder to gain electron |
| Oxidising power | Decreases | Less able to accept electron |
Displacement Reactions – Memorise This Table!
A more reactive halogen displaces a less reactive one from its compound:
- Cl₂ + 2KBr → 2KCl + Br₂ (brown colour appears)
- Cl₂ + 2KI → 2KCl + I₂ (black solid / purple vapour)
- Br₂ + 2KI → 2KBr + I₂ (brown → purple)
- I₂ + KCl → no reaction
Memorise Group 7 in 60 Seconds – Song Hack
Maximum Internal Links (SEO Power)
- → Cambridge Periodic Table PDF 2025–2027
- → Group 7 Halogens Full Notes + Worksheet
- → Cations & Anions + Halide Test Cheat Sheet
- → O Level Chemistry Formula Sheet PDF
- → IGCSE 0620 Solved Past Papers
- → O Level 5070 Solved Past Papers
Group 7 Past Paper Questions Solved by Prof. Faisal
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