1) How do lone pairs of electrons influence the structure of molecules? 2) What
ID: 229720 • Letter: 1
Question
1) How do lone pairs of electrons influence the structure of molecules?
2) What does VSEPR stand for? In VSEPR theory, what determines the shape of the molecule?
3) Draw an appropriate Lewis structure for the following molecules and attempt to predict their shape: H2S, CH4, XeF4
4) Give a molecular example for each type of intermolecular force: (a) dipole-dipole (b) ion-dipole (c) dispersion forces (d) van der Waals forces 5) Determine if the molecules from question 3 are polar or nonpolar. Explain your answer.
Explanation / Answer
(1)
The presence of lone electrons pushes non-central atoms toward one another in molecules,. Because the only atom pulling on the lone pair of electrons is the central atom, these are drawn closer to the central atom than the non-central atoms are. Thus, the lone pairs of electrons take up more space and push away the non-central atoms. The textbook example is the difference between CH4, NH3, and H2O.
All three have sp3 hybridization, but they have 0, 1, and 2 lone pairs of electrons around the central atom respectively. Thus, NH3 has a smaller bond angle than CH4 because its electron pair pushes the hydrogen atoms together, and that of H2O is even smaller because 2 electron pairs push the hydrogen atoms even closer together.
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