Reason for Greater Dipole Moment in NH3 compared to NF3
- Electronegativity Difference: While fluorine is more electronegative than hydrogen, the difference in electronegativity between nitrogen and hydrogen is greater than that between nitrogen and fluorine. This results in a stronger dipole moment in NH3 compared to NF3.
- Geometry: NH3 has a pyramidal shape with a lone pair of electrons on nitrogen, leading to an uneven distribution of charge and a higher dipole moment. On the other hand, NF3 has a trigonal pyramidal shape but all the fluorine atoms are identical, resulting in a more symmetrical distribution of charge and a lower dipole moment.
- Lone Pair-Lone Pair Repulsion: The lone pair on nitrogen in NH3 experiences repulsion from the other lone pairs, causing the molecule to be more polar compared to NF3 where all the fluorine atoms are bonded to nitrogen and there are no lone pairs repelling each other.
- Overall Polarity: The combination of the greater electronegativity difference, geometry, and lone pair-lone pair repulsion in NH3 leads to a higher overall dipole moment compared to NF3, despite fluorine being more electronegative than hydrogen.