2.2.4—VSEPR model

VSEPR predicts molecular shape by arranging electron domains around a central atom to minimize repulsion. Lone pairs repel more strongly than bonding pairs and therefore alter common bond angles.

Step	Decision
1	Count bonding and lone-pair electron domains
2	Assign electron-domain geometry
3	Ignore lone pairs when naming molecular geometry
4	Adjust expected bond angles for lone-pair repulsion

NH₃ has four electron domains around N, so its electron-domain geometry is tetrahedral but its molecular shape is trigonal pyramidal; the lone pair compresses the H–N–H angle below 109.5°. Count a double bond as one domain and distinguish electron geometry from the shape named using atoms only.

Representative question

[Maximum number: 2]

Deduce the electron domain geometry and molecular geometry of $\mathrm{SO}_{2}$ .

Electron domain geometry:

Molecular domain geometry:

Retrieve the covalent pathway: shared pairs and bond order lead to geometry, polarity and molecular polarity; structure determines network properties, IMF behaviour and chromatography; HL representations extend to resonance, formal charge, sigma/pi bonds and hybridization.

Check the representation first, then count domains, apply geometry, identify polarity or forces, and connect the structure to the requested property or HL bonding description.

2.2.4—VSEPR model

VSEPR Geometry

Applying VSEPR

Assessment in practice

The Covalent Model Summary

Question 1