1. Molecular Geometry

2. Basic Terminology Molecule Group of atoms held together by covalent bonds Bond Length Distance between 2 bonded atoms Bond Energy Energy required/needed to break a chemical bond Bond Angles Determined based on bonding and nonbonding regions of the central atom in a molecule

3. Why is molecular shape/structure SO important?

4. Molecular Shape 3-D structure of a molecule Predicted from the Lewis dot diagram of a chemical compound

5. “VSEPR” Theory/Electron Domain (ED) Model Valence electrons repel each other Electrons are arranged so the distance between them is MAXIMIZED ! Electron pair orientations influence the shape/structure of a molecule Focus on central atom Shared electrons Unshared electrons

6. Ex. BeF 2

7. What about unshared electrons on the central atom? Lone/unshared electrons Occupy space around central atom Not involved in chemical bonding between atoms These pairs are NOT taken into account for a chemical molecule’s shape ! Require MORE space than shared electrons, indirect contribution to shape

8. Molecular Shapes 1) Bent 2) Trigonal Pyramidal 3) Tetrahedral 4) Trigonal Planar 5) Two atom Linear 6) Linear

9. 1) Bent Ex. H 2 O

10. 2) Trigonal Pyramidal Ex. NH 3

11. 3) Tetrahedral Ex. CH 4

12. 4) Trigonal Planar Ex. BF 3

13. 5) Two atom Linear Ex. I 2

14. 6) Linear Ex. CaCl 2