Chemical Bonding and Molecular Structure · Class 11

VSEPR Theory

VSEPR theory explained: electron pair repulsion, molecular shapes, bond angles, and examples for Class 11, JEE and NEET.

Direct answer

VSEPR (Valence Shell Electron Pair Repulsion) theory predicts molecular shape from the arrangement of electron pairs around the central atom that minimises repulsion.

Core idea

Electron pairs (bonding pairs and lone pairs) around a central atom repel each other and stay as far apart as possible.

Lone pair–lone pair repulsion > lone pair–bond pair > bond pair–bond pair. That is why H₂O (~104.5°) and NH₃ (~107°) are bent / pyramidal, not the ideal tetrahedral 109.5°.

Shapes you must know

Linear — BeCl₂, CO₂

Trigonal planar — BF₃

Tetrahedral — CH₄

Trigonal pyramidal — NH₃

Bent (angular) — H₂O

Trigonal bipyramidal — PCl₅

Octahedral — SF₆

Square planar — XeF₄

VSEPR vs hybridisation

VSEPR predicts shape from electron-pair geometry.

Hybridisation is a bonding model that often matches that geometry (e.g. tetrahedral → often sp³).

Use both: VSEPR for shape; hybridisation for orbital language in exams.

Tip · Grewal Sir’s Tip: Always decide the electron-pair geometry first, then the molecular shape after placing lone pairs.

Common mistake · Confusing electron geometry with molecular shape (e.g. saying NH₃ is tetrahedral molecule — the electron geometry is tetrahedral; the molecular shape is trigonal pyramidal).

Exam trap · Questions on bond angle order (e.g. NH₃ vs H₂O vs CH₄) test lone-pair repulsion, not memorisation of hybridisation labels alone.