Although both CO₂ and H₂O are triatomic molecules, the shape of H₂O molecule is bent while that of CO₂ is linear. Explain this on the basis of dipole moment.
In polyatomic molecules, the dipole moment depends on individual bond dipoles and the spatial arrangement of various bonds.
In , the bent structure orients the two O–H bonds at an angle of . The bond dipoles do not cancel each other, resulting in a net dipole moment of C m.
In , the molecule is linear. The two equal bond dipoles point in opposite directions and cancel the effect of each other, resulting in a zero net dipole moment. This difference in resultant dipole moments explains why is bent while is linear.
Explanation
The textbook context explains that dipole moments in polyatomic molecules depend on bond dipoles and their spatial arrangement. For H2O, the bent structure at 104.5 degrees means bond dipoles add up to a net dipole moment. For linear molecules like BeF2 (and similarly CO2), equal bond dipoles point in opposite directions and cancel out, giving zero net dipole moment. This contrast in spatial arrangement and resulting dipole moments explains the difference in their shapes.