Previous Year Question Patterns (NEET 2015-2024)
High-Frequency Topics in Groups 16-18:
| Topic | Frequency | Typical Question Type |
|---|---|---|
| Contact process — oleum formation (Step 3) | Very High | Fact-based, reason-based |
| XeF2 geometry (linear, 3 lone pairs) | Very High | Shape/hybridization MCQ |
| XeF4 geometry (square planar, 2 lone pairs) | High | Shape/hybridization MCQ |
| Halogen oxoacid strength order | High | Order/comparison MCQ |
| HF as weak acid | High | Reasoning MCQ |
| V2O5 catalyst at 450°C | Moderate | Conditions-based MCQ |
| Interhalogen compound shapes | Moderate | Table completion |
| KI-starch test for ozone | Moderate | Reaction identification |
| Sulfur allotropes | Low | Factual MCQ |
Recurring NEET Question Themes:
Theme 1: "Why is SO3 not dissolved in water directly?" → Answer: Forms fine acid mist; absorbed in H2SO4 to give oleum
Theme 2: "Shape and hybridization of XeF2/XeF4/XeF6" → Trick: Linear (not bent), Square planar (not tetrahedral), Distorted octahedral
Theme 3: "Correct order of oxoacid strength for Cl" → HOCl < HClO2 < HClO3 < HClO4; increases with oxidation state
Theme 4: "Why HF is weakest HX acid" → Answer: Strongest H-F bond + intermolecular H-bonding
Exam Strategy: For Groups 16-18, focus 60% effort on xenon compound geometries + Contact process. These two areas generate ~2-3 direct questions every few years in NEET.