Editing Lone pair (section)

==Dipole moments==
Lone pairs can contribute to a molecule's [[molecular dipole moment|dipole moment]]. [[Ammonia|NH<sub>3</sub>]] has a dipole moment of 1.42 D. As the [[electronegativity]] of nitrogen (3.04) is greater than that of hydrogen (2.2) the result is that the N-H bonds are polar with a net negative charge on the nitrogen atom and a smaller net positive charge on the hydrogen atoms. There is also a dipole associated with the lone pair and this reinforces the contribution made by the polar covalent N-H bonds to ammonia's [[molecular dipole moment|dipole moment]]. In contrast to NH<sub>3</sub>, [[nitrogen trifluoride|NF<sub>3</sub>]] has a much lower dipole moment of 0.234 D. Fluorine is more [[electronegativity|electronegative]] than nitrogen and the [[bond dipole moment|polarity]] of the N-F bonds is opposite to that of the N-H bonds in ammonia, so that the dipole due to the lone pair opposes the N-F bond dipoles, resulting in a low molecular dipole moment.<ref>{{Housecroft2nd|page=40}}</ref>