1. Predict the geometry of the molecule from the electrostatic repulsions between the electron (bonding and nonbonding) pairs. Valence shell electron pair repulsion (VSEPR) model: This chart is NOT provided on the AP exam! The idea here is that the bonding and nonbonding pairs around a given atom will be positioned as far apart as possible.

2. VSEPR AB 2 20 Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry linear B B A = central atom B = atoms bonded to central atom E = lone pairs (non-bonding) of electrons on central atom Bond angle

3. Cl Be 2 atoms bonded to central atom 0 lone pairs on central atom

4. AB 2 20linear Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry VSEPR AB 3 30 trigonal planar

6. Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry VSEPR – Trigonal Planar arrangement AB 3 30 trigonal planar AB 2 E21 trigonal planar bent

7. AB 2 20linear Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry VSEPR AB 3 30 trigonal planar AB 4 40 tetrahedral

9. Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry VSEPR – Tetrahedral Arrangement AB 3 E31 AB 4 40 tetrahedral trigonal pyramidal

10. Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry VSEPR – Tetrahedral Arrangement AB 4 40 tetrahedral AB 3 E31tetrahedral trigonal pyramidal AB 2 E 2 22tetrahedral bent H O H

11. CH 4 NH 3 H2OH2O Number of lone pairs 012 Bond angle109.5 o 107 o 104.5 o In these molecules, the arrangement of the electron pairs predict tetrahedral geometry. Why is the geometry different from predicted? Lone pairs require more room than bonding pairs and tend to compress the angles between the bonding pairs.

12. AB 2 20linear Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry VSEPR AB 3 30 trigonal planar AB 4 40 tetrahedral AB 5 50 trigonal bipyramidal trigonal bipyramidal

14. Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry VSEPR – Trigonal Bipyramidal Arrangement AB 5 50 trigonal bipyramidal trigonal bipyramidal AB 4 E41 trigonal bipyramidal See-Saw (distorted tetrahedron)

15. Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry VSEPR – Trigonal Bipyramidal Arrangement AB 5 50 trigonal bipyramidal trigonal bipyramidal AB 4 E41 trigonal bipyramidal See-Saw AB 3 E 2 32 trigonal bipyramidal T-shaped Cl F F F

16. Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry VSEPR – Trigonal Bipyramidal Arrangement AB 5 50 trigonal bipyramidal trigonal bipyramidal AB 4 E41 trigonal bipyramidal See-Saw AB 3 E 2 32 trigonal bipyramidal T-shaped AB 2 E 3 23 trigonal bipyramidal linear I I I

17. AB 2 20linear Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry VSEPR AB 3 30 trigonal planar AB 4 40 tetrahedral AB 5 50 trigonal bipyramidal trigonal bipyramidal AB 6 60 octahedral

19. Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry VSEPR – Octahedral Arrangement AB 6 60 octahedral AB 5 E51 octahedral square pyramidal Br FF FF F

20. Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry VSEPR – Octahedral Arrangement AB 6 60 octahedral AB 5 E51 octahedral square pyramidal AB 4 E 2 42 octahedral square planar Xe FF FF

21. Predicting Molecular Geometry 1.Draw Lewis structure for molecule. 2.Count number of lone pairs on the central atom and number of atoms bonded to the central atom. 3.Use VSEPR to predict the geometry of the molecule. What are the molecular geometries of SO 2 and SF 4 ? (In SF 4, S uses an expanded octet of 10.) AB 2 Ebent S F F F F AB 4 E See-Saw (distorted Tetrahedron) S O O S O O

22. Dipole Moments and Polar Molecules H F electron rich region electron poor region   A molecule such as HF that has a center of positive charge and a center of negative charge is said to have a dipole moment. The dipole moment is often represented by an arrow pointing to the negative charge center with the tail of the arrow indicating the positive center of charge.

23. Which of the following molecules have a dipole moment? H 2 O, CO 2, SO 2, and CH 4 O H H dipole moment polar molecule S O O CO O no dipole moment nonpolar molecule dipole moment polar molecule C H H HH no dipole moment nonpolar molecule