1. Section 5.3—Molecules in 3D

2. Bonds repel each other
Bonds are electrons. Electrons are negatively charged
Negative charges repel other negative charges
Bonds repel each other
Molecules arrange themselves in 3-D so that the bonds are as far apart as possible

3. Valence Shell Electron Pair Repulsion Theory (VSEPR Theory)
This theory (that bonds repel each other because they have like charges) attempts to explain why molecules form the shapes they form. Lewis Dot’s only allow us to see in 2-D! VSEPR allows us to visualize in 3-D!

5. What shapes do molecules form?
Linear
2 bonds, no lone pairs
Indicates a bond going away from you
Trigonal planar
3 bonds, no lone pairs
Indicates a bond coming out at you

6. What shapes do molecules form?
Tetrahedron
4 bonds, no lone pairs

7. Lone Pairs
Lone pairs are electrons, too…they must be taken into account when determining molecule shape since they repel the other bonds as well.
But only take into account lone pairs around the CENTRAL atom, not the outside atoms!

8. What shapes do molecules form?
Bent
2 bonds, 1 lone pair

10. What shapes do molecules form?
Bent
2 bonds, 2 lone pairs

11. What shapes do molecules form?
Trigonal pyramidal
3 bonds, 1 lone pair

12. Ionic Compound structures
Ionic compounds are made of positive and negative ions.
They pack together so that the like-charge repulsions are minimized while the opposite-charge attractions are enhanced.
Na+1
Cl-1