How do you determine the molecular shape of a compound?

Answer 1

Experimentally a number of methods are used, examining crystal structures using X-Ray crystallography, neutron diffraction, or electron diffraction. Using spectrographic techniques such as rotational/vibrational spectra, infrared or Raman spectroscopy on solids, liquids or gases or electron diffraction on gases.

As a predictive tool VSEPR is useful for simple molecules with a central atom allowing a qualitative understanding of the shape. Fro many organic molecules ball and stick modelling using typical bond angles and bond lengths is insightful as it highlights potential steric constraints where one part of a molecule is cannot adopt one position because of the proximity of other atoms. Another effect may be attraction between one part of a molecule and another for example intramolecular hydrogen bonding.