VSEPR: build a molecule's shape
"VSEPR: build a molecule's shape" is a free, interactive Class 11 Chemistry simulation for NEET and JEE, built on the lesson "VSEPR theory and molecular shapes" in Chemical Bonding and Molecular Structure. Pick how many bond pairs and lone pairs sit around the central atom. Drag the molecule to turn it. Watch the shape name: it counts only atoms, not lone pairs. Count all electron pairs round the central atom (a double bond counts as one region) to get the electron geometry; the shape is what the atoms make. Lone pairs squeeze bond angles and, in a trigonal bipyramid, take equatorial places. JEE Main asked 47 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson VSEPR theory and molecular shapes in Chemical Bonding and Molecular Structure. Change the values and watch what happens.
In JEE Main
42 shifts analysed
47 questions from Chemical Bonding and Molecular Structure across the 42 JEE Main shifts Lumi has analysed (2017–2026).
The idea behind it
NCERT § "The Valence Shell Electron Pair Repulsion (VSEPR) Theory"
- The shape of a molecule is set by the number of electron pairs (bonding and lone) around the central atom, which arrange themselves as far apart as possible.
- A multiple bond is treated as a single electron-pair region (a 'super pair') when predicting shape.
- Repulsion order: lone pair-lone pair > lone pair-bond pair > bond pair-bond pair, because lone pairs are held by only one nucleus and spread out more.
- Without lone pairs: 2 pairs linear (BeCl₂, 180°), 3 trigonal planar (BF₃, 120°), 4 tetrahedral (CH₄, 109.5°), 5 trigonal bipyramidal (PCl₅), 6 octahedral (SF₆).
- With lone pairs and 4 regions: NH₃ (3 bond pairs, 1 lone pair) is trigonal pyramidal with about 107°; H₂O (2 bond pairs, 2 lone pairs) is bent with about 104.5°.
- With 5 regions, lone pairs take equatorial positions: SF₄ (4 bp, 1 lp) is see-saw and ClF₃ (3 bp, 2 lp) is T-shaped. Background from the Class 12 noble-gas chapter, not in this chapter's table: XeF₂ (2 bp, 3 lp) is linear by the same rule.
- With 6 regions: BrF₅ (5 bp, 1 lp) is square pyramidal and XeF₄ (4 bp, 2 lp) is square planar.
- SO₂ and O₃, each with 3 regions including one lone pair, are bent.
- Molecular shape names describe the positions of atoms only; lone pairs affect the shape but are not part of its name.
Questions
3 answers
- What does the "VSEPR: build a molecule's shape" simulation show?
- Pick how many bond pairs and lone pairs sit around the central atom. Drag the molecule to turn it. Watch the shape name: it counts only atoms, not lone pairs.
- Does JEE Main ask questions from Chemical Bonding and Molecular Structure?
- Yes. JEE Main asked 47 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "VSEPR theory and molecular shapes" in Chemical Bonding and Molecular Structure (Class 11 Chemistry).
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