How to predict shape of Molecules

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Predict polarity based on electron arrangement

A molecule’s shape and polarity are directly related.A chemical bond becomes polar if the electro negativity difference is more than 0.5 between the atoms that share the bond.This polarity in a bond is called a bond dipole. This concept can be applied to molecules to predict polarity.

Compare two molecules with the same molecular shape: CCl4 and CCl3H. Since the polarity of the C-Cl bond is different from that of the C-H bond, the polarities of these two molecules are different. The CCl4 molecule is symmetrical about any axis joining the two atoms of the CCl bond. The polarities of the C-Cl bonds counteract one another. Thus, the carbon  tetrachloride molecule is non-polar. In the case of CCl3H, the polarity of the H-Cl bond is different from that of the three C-Cl bonds. Thus, the molecule is polar.

predict shape of molecules

The following table shows the effect of Molecular Shape on Molecular Polarity

molecular polarity table

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