Question

Carbon dioxide is non-polar while water is polar. What conclusion do you draw about their structures from these.

Answer 1

Both the molecules are triatomic and there is electronegativity difference between C-O as well as O-H. But their polarity difference indicates that their structures are different. The difference in polarity is due to the symmetries of the molecules. Since CO2 is non polar and central atom has no lone pairs, it shows that both of the oxygen atoms are on opposite sides of carbon thereby cancelling the dipole moment and making the molecule linear.

H2O being polar indicates that both the hydrogen atoms are on one side and the lone pair of electrons on the central atom is on the other side and due to bond pair-lone pair repulsion , the geometry of the molecule is bent. The contribution in the polarity is the dipole moment from the lone pair.