ChemistryChapter 12: Halogens
Oxidising Power and Displacement — Why
Oxidising power falls down Group 17 because atoms get larger and more shielded, electronegativity falls, and gaining an electron becomes les
Learning objectives
- Explain Oxidising Power and Displacement — Why using Group 17 language.
- Link trends to size, shielding, forces and bond strength.
- Apply equations and observations in FBISE-style answers.
Definition
Oxidising power falls down Group 17 because atoms get larger and more shielded, electronegativity falls, and gaining an electron becomes less favourable. So F₂ is fiercest and I₂ mildest; halide reducing power rises toward I⁻.
Core Concept
Down group: radius↑ shielding↑ EN↓ → oxidising power of X₂↓ Reducing power of X⁻↑ (I⁻ strongest of Cl⁻/Br⁻/I⁻) Explains displacement order · Parent: Oxidising Power and Displacement
Beginner
Big halogen atoms grab electrons less strongly. So oxidising power goes down the group. That is why chlorine beats bromide/iodide but iodine cannot beat chloride.
Intermediate
State size/shielding/EN → oxidising trend. Link explicitly to which displacements work. Mention I⁻ as strongest reductant in the triad.
Advanced
Electron-gain favourability declines down the group in the school model; compare with electron affinity nuances only if the syllabus asks — Class answers should stay with size, shielding, and EN.
Remember
Larger down group → weaker X₂ oxidant · I⁻ strongest reductant · explains Cl₂>Br₂>I₂ behaviour · parent oxidising topic.
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Oxidising Power and Displacement — Why
Sticky Notes · Quick Revision
Cause
- radius↑
- shielding↑
- EN↓
Effect
- oxidising power↓
- F₂>Cl₂>Br₂>I₂
Halide side
- reducing power↑ down
- I⁻ strongest
Parent
- oxidising power and displacement
- why
60-second revision
- Size and EN explain falling oxidising power.
- I⁻ is the strongest reductant of Cl⁻/Br⁻/I⁻.
- This “why” underpins displacement rules.
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