CBSE Class 11-science Answered

A permanent dipole is when you have a polar molecule with oppositely charged ends, and these ends attract other polar molecules, bonding them together. The polar molecules will always be slightly negative on one end and slightly positive on the other. The slightly negative attracts the slightly positive on another molecule, and the slightly positive attracts the slightly negative on another molecule. Therefore, they bond together. (Permanent dipoles are found in the dipole-dipole forces.) Example H₂O and NH₃ have permanent dipole moment. Permanent dipoles form when the structure of the molecule is such that there is an asymmetry of electronegativity amongst atoms bonded to a central atom. For example, CH4 is nonpolar but CH3F is polar because F has a higher EN than the three other H's bound to the central atom). Lone pairs on the central atom (such as in H2O and NH3) also lead to permanent polarity.