Question

Why dipole moment is more than cl compared to fluoride?

Answer 1

And accordingly: Methyl chloride has a central carbon atom surrounded by three hydrogen atoms and one chlorine atom. The molecule has a tetrahedral shape. The hydrogen atoms are less electronegative than the carbon atom, so the electrons in the carbon-hydrogen bonds are unequally shared. They are present closer to the carbon atom, thus giving the hydrogen atoms a partial positive charge. Chlorine is more electronegative than carbon and attracts the bonded electron pair in the carbon-chlorine bond towards itself, thus obtaining a partial negative charge. The molecule is a dipole with a partial positive and a partial negative center, thus making methyl chloride a polar molecule. Moreover Methyl chloride (CH3Cl) has a tetrahedral shape with a bond angle of 109.5 degrees. This is because carbon has four valence electrons forming four bonds and in a three-dimensional space, a tetrahedral shape allows for the bonded electrons to be furthest away from each other.

Now as per your question the dipole moment is based on the product of distance and charge, and not just charge alone. No doubt Fluorine is more electronegative than chlorine, but, the carbon-fluorine bond is also much shorter than the carbon-chlorine bond: 139 pm vs 178 pm because of strong attraction of electron pair of Carbon by Fluorine . That's why the dipole moment of chloromethane is higher than the dipole moment of fluoromethane.

See the structure of fluoromethane