Final answer:
The VSEPR model can be used to determine the molecular geometries of molecules with expanded valence shells. Two examples are PF5 and H3O+.
Step-by-step explanation:
The molecular geometries of molecules with expanded valence shells can be determined using the VSEPR model. The VSEPR model states that electron pairs repel each other to get as far away from each other as possible. Two examples of molecules with expanded valence shells are PF5 (phosphorus pentafluoride) and H3O+ (hydronium ion).
1. PF5: Phosphorus has 5 valence electrons and each fluorine atom contributes 1 valence electron, making a total of 10 valence electrons. The molecular geometry of PF5 is trigonal bipyramidal, with the phosphorus atom in the center and the five fluorine atoms surrounding it. The bond angles are 90° and 120°.
2. H3O+: Oxygen has 6 valence electrons and each hydrogen atom contributes 1 valence electron, making a total of 9 valence electrons. The molecular geometry of H3O+ is trigonal pyramidal, with the oxygen atom in the center and the three hydrogen atoms surrounding it. The bond angle is approximately 107°.