1. Shapes of Molecules Determined by number of valence electrons of the central atom 3-D shape a result of bonded pairs and lone pairs of electrons Use VSEPR theory (valence-shell-electron-pair repulsion 1

2. What is VSEPR Theory Valence Shell Electron Pair Repulsion Theory- This just means that electrons will adjust themselves as far away from each other as possible. Non-bonded electrons (unshared) have more of a repulsion. 2

3. Using the VSEPR Model 1. Identify the central atom ***NEVER HYDROGEN*** This is a terminal atom. Usually it is the first element in the compound. 2. Draw the electron-dot structure 3. Count the total number of electron pairs around central atom 4. Predict the shape of the molecule using the bonding atoms 3

4. Shapes of Molecules Number of bonded atoms 2 Name of shape linear There are NO unshared pairs of electrons on the central atom

5. BeCl 2 Be 2 valence electrons.... : Cl : Be : Cl :.... : Cl Be Cl : linear.... 5

6. More Electron Pairs Atoms Bonded PairsShape 3 3trigonal planar Timberlake LecturePLUS 6

7. Electron Shape with 3 Pairs 7

8. BF 3 B has 3 valence electrons Ftrigonal planar B F No unshared pairs on the central atom 8

9. More Electron Pairs Electron Bonded Name of PairsAtomsShape 4 4tetrahedral 4 3pyramidal 4 2bent 9

10. Tetrahedral CH 4 4 electron Pairs, 4 bonded atoms, NO UNSHAIRED PAIRS 10

11. NH 3 Pyramidal N has 4 electron pairs, 3 bonded H atoms Shape is called pyramidal ONE UNSHARED PAIR.. H : N : H N.. HH H H 11..

12. H 2 O Bent or Angular O has 4 electron pairs, 2 bonded H atoms Shape is called bent 2 UNSHARED PAIRS.. : O : H O.. H H H 12..

13. Learning Check Determine the molecular geometry of each of the following: A. CCl 4 1) tetrahedral 2) pyramidal3)Bent B. SO 3 1) trigonal planar 2) pyramidal3) Bent C. PCl 3 1) trigonal planar 2) pyramidal3) Bent 13

14. Solution Determine the molecular geometry of each of the following: A. CCl 4 1) tetrahedral B. SO 3 1) trigonal planar C. PCl 3 2) pyramidal 14