Why the dipole moment of CH3F is greater than that of CH3Cl even thoughthe electronegativity of F is greater than Cl

The dipole moment of a molecule depends on two factors: the difference in electronegativity between the atoms and the distance between the atoms.

1. Electronegativity: Fluorine is more electronegative than chlorine, which means it pulls electrons towards itself more strongly. This creates a larger charge difference and thus a larger dipole moment.

2. Distance: However, the C-F bond length is shorter than the C-Cl bond length. This is because fluorine is a smaller atom than chlorine. The dipole moment is the product of the charge difference and the distance between the charges. So, even though the charge difference in C-Cl might be less, the longer distance can lead to a larger dipole moment.

In the case of CH3F and CH3Cl, the effect of the electronegativity difference outweighs the effect of the bond length. Therefore, CH3F has a larger dipole moment than CH3Cl.