Chemical Bonding and Molecular Structure

4.16. Significance of dipole moment are:

In predicting the nature of the molecules: Molecules with specific dipole moments are polar in nature and those of zero dipole moments are non-polar in nature.

In the determination of shapes of molecules.

In calculating the percentage ionic character.

4.15. In CO₂, there are two C=O bonds. Each C=O bond is a polar bond. The net dipole moment of CO₂ molecule is zero. This is possible only if CO₂ is a linear molecule. (O=C=O). The bond dipoles of two C=O bonds cancel the moment of each other.

Whereas, H₂O has a net dipole moment of 1.84 D. H₂O molecule has a bent structure because here the O—H bonds are oriented at an angle of 104.5° and do not cancel the bond moments of each other.

 

4.12. No, these cannot be taken as canonical forms because the positions of atoms have been changed. 

4.11. 

Resonance in CO₃^2-, I, II and III represent the three canonical forms.

In these structures, the position of nuclei is the same.

The Lewis dot structure has two single bonds and one double bond.

All three forms have almost equal energy.

The three forms have same number of paired and unpaired electrons; they differ only in their position.

4.10. Bond-length: It is the equilibrium distance between the nuclei of two bonded atoms in a molecule. Bond-lengths are measured by spectroscopic methods.

4.9. Bond strength is directly proportional to the bond order. Greater the bond order more is the bond strength.

4.8. Because of two lone pairs of electrons on O-atom, repulsion on bond pairs is greater in H₂O in comparison to NH₃. Thus, the bond angle is less in H₂O molecules.

4.7