Concept 5 - Molecular Geometry

What does a chemical formula tell us?

It tells us what elements make up a molecule (e.g., C₆H₁₂O₆).

What does a structural formula show?

A 2D picture of a molecule’s structure.

What theory explains the shapes of molecules?

VSEPR Theory (Valence Shell Electron Pair Repulsion).

Why do electron pairs arrange themselves as far apart as possible?

Because valence electrons repel each other.

What is an electron domain?

The space occupied by electrons, including bonding pairs, lone pairs, or multiple bonds.

What molecular shape has 2 electron domains?

Linear (e.g., O₂ and HCN).

What molecular shape has 3 electron domains?

Trigonal planar (e.g., BF₃).

What molecular shape has 4 electron domains and no lone pairs?

Tetrahedral (e.g., CH₄).

What molecular shape has 5 electron domains?

Trigonal bipyramidal (e.g., PCl₅).

What molecular shape has 6 electron domains?

Octahedral (e.g., SF₆).

What molecular shape has 4 electron domains, 2 bonding pairs, and 2 lone pairs?

Bent (e.g., H₂O).

What molecular shape has 4 electron domains, 3 bonding pairs, and 1 lone pair?

Trigonal pyramidal (e.g., NH₃).

How are 3D molecular structures represented on paper?

By using notation to show the 3D shape or by building 3D models.

What is the shape of CH₂O?

Trigonal planar (3 electron domains, 0 lone pairs).

What is the shape of CO₂?

Linear (2 electron domains, 0 lone pairs).

What is the shape of SCl₂?

Bent (4 electron domains, 2 lone pairs).