1. Valence Shell Electron Pair Repulsion Theory Based on electrostatic “like repels like” – electrons repel other electrons So Electron pairs (both shared and unshared) will arrange themselves based on the mutual repulsion Unshared pairs of electrons are non-directional and so they repel more than shared pairs Shared pairs of electrons are more directional (between the two atoms) so they repel a little less than the unshared pairs

2. Tetrahedral This shape is the base for anything with four bonding “sites”, both shared pairs (bonds) or lone pairs Note that this is not a “ + ” like how we draw it on paper, but an object that fills all three dimensions. Dark Wedges show bonds coming out of the page Dashed lines show bonds going into the page

3. Trigonal Pyramidal (based on tetrahedral) 4 sides (3 bonds – shared pairs, 1 lone pair) Lone pair repels more than shared pair Pushes the bonds down more Bond angle is less than tetrahedral < 109.5°(~ 107.3°)

4. Bent (based on tetrahedral) 4 sides (2 bonds – shared pairs, 2 lone pairs) Lone pairs repels more than shared pairs Pushes the bonds down even more Bond angle is less than tetrahedral and trigonal pyramidal < 109.5° < 107.3° (~ 104.5°)

5. Trigonal Planar 3 sides (3 bonding sites – consider double bonds as one bonding site, no lone pairs) Mutual repulsion from three sides Flat (planar) 360° / 3 sides = 120° (Bond angle)

6. Bent (based on trigonal planar) 3 sides (2 bonding sites – consider double bonds as one bonding site, 1 lone pair) Lone pair repels more than shared pairs Pushes the bonds down even more Bond angle is less than trigonal planar < 120° Note that this “Bent” is different from the other “Bent” This has 3 sides so it is based on a trigonal planar configuration While the other one is has four sides so it is based on a tetrahedral configuration

7. Linear 2 sides (2 bonding sites – consider double and triple bonds as one bonding site) Bond angle 180°

8. Read Sections 8.1 – 8.3