In: Chemistry
Explain why only the lone pairs on the central atom are taken into consideration when predicting molecular shape.
Is it because lone pairs have greater repulsion than bonded electrons? if so, why do electrons on outter atoms not determin the shape of the molecule?
The shape of a moleculed is determined by the most stable configuration i.e. configuration where repulsive force is minimum.The magnitude of repulsive force between electron pair follows the following order:bond pair-bond pair<bond pair-lone pair<lone pair-lone pair.Since repulsive force is maximum between lone pairs,the molecule assumes a shape where the lone pairs on the central atom are at maximum distance from each other for achieving the most stable configuration.
Since electrons on outer atoms are bonded to central atom,the repulsive force between the bonded pairs is less significant compared to that between lone pairs.Hence ,lone pairs on central atom play a decisive role in determining the shape of a molecule.