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HOW DOES THE PRESENCE OF A LONE PAIR AFFECT THE NET DIPOLE MOMENT OF A COMPOUND ? AND ALSO HOW TO FIND THE DIRECTION OF DIPOLE MOMENT DUE TO THE LONE PAIR ??

HOW DOES THE PRESENCE OF A LONE PAIR AFFECT THE NET DIPOLE MOMENT OF A COMPOUND ? AND ALSO HOW TO FIND THE DIRECTION OF DIPOLE MOMENT DUE TO THE LONE PAIR ??

Grade:Upto college level

2 Answers

Aarti Gupta
askIITians Faculty 300 Points
10 years ago
Lone pair is a valence e- pair which is not shared with another atom and is sometimes called a non-bonding pair.For ex. NH3 has 1 lone pair H2O has 2 lone pair.
Lone pairs can make a contribution to a molecule's dipole moment. NH3 has a dipole moment of 1.47 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 dipole moment. In contrast to NH3,NF3 has a much lower dipole moment of 0.24 D. Fluorine is more electronegative than nitrogen and the 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.
Lone pair electrons have effect on the net dipole moment of a molecule. A dipole moment is the product of the magnitude of the partial charges on the molecule and the distance in which they are separated. Lone pair electrons affect both the partial charges and the distance between partial charges.
Thanks & regard
Aarti Gupta
askiitains Faculty
Vishal Sharma
34 Points
10 years ago
according to vsepr theory : the maximum repulsion is found in loan pair :loan pair. loan pair : bond pair and bond pair : bond pair. now comming 2 ur question: if there will be loan pair present then it will cause repulsion and as a result bond angle will get effected. u can take example of water & ammonia , both have loan loan pair repulsion in them so their bond angle is effected due 2 this .

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