Structure and bonding: 2.20 - Shapes of molecules

The shape of molecule (or ion) is the shape adopted by the atoms in a molecule (or ion) with respect to one another.

Confusion arises occasionally, because the shape adopted by the regions of electronic charge (electron domains) around an atom has to be known before determining the location of the atoms. Students confuse this electronic organisation with the molecular shape. In fact, they may be the same, but often they are not.

Structure 2.2.4 - The valence shell electron pair repulsion (VSEPR) model enables the shapes of molecules to be predicted from the repulsion of electron domains around a central atom.

Predict the electron domain geometry and the molecular geometry for species with up to four electron domains.

Guidance

Include predicting how non-bonding pairs and multiple bonds affect bond angles.

Tools and links

Nature of science - How useful is the VSEPR model at predicting molecular geometry?

In Section 2.2

2.21 - Valence Shell Electron Pair Repulsion theory
2.22 - 2, 3 and 4 electron domain molecules and ions
2.23 - 5 and 6 electron domain molecules and ions
2.24 - Resonance
2.25 - Delocalisation
2.26 - Hybridisation
2.27 - Molecular orbital theory
2.28 - Aromatic compounds