University:
Boston University
Course:
CAS PY 242 | Principles of General Physics 2
Academic year:

2022
Views:

19

Pages:

1
Author:

unrememberedx6wyi

Lone pairs affect polarity TP Lone pairs can either enhance or diminish the contribution of bond dipoles to the polarity of a molecule. Which molecule is more polar? Lone pairs contribute to localize negative charge on an atom. The effect of lone pairs alone is why the T‐shaped molecule I4 is polar, even though each bond is none polar. 1. NH3 2. NF3 3. Each of the above is nonpolar Lone pairs affect polarity Lone pairs affect polarity Lone pairs can either enhance or diminish the contribution of bond dipoles to the polarity of a molecule. An example of a consequence of this that NH3 is more polar has a larger dipole moment; see section 7‐11, page 226 than NF3. In the series of T‐shaped molecules ClF3, BrF3, and IF3 problem 7.36 , the lone pairs oppose the shifts in bonding electron clouds and so diminish the polarity of each molecule. Note that the arrows in the figure show the shift in the electron clouds due to the electronegativity differences. However, since the effect of the lone pairs is the same in each molecule, their relative polarities mirror their relative bond polarities. The lone pairs in NH3 augment the cloud shifts in the N‐H bonds, and so enhance the polarity. The lone pairs in NF3 oppose the cloud shifts in the N‐F bonds, and so diminish the polarity. Therefore, the order of molecular polarities is ClF3 BrF3 IF3