1. Chemical Bonding and Molecular Structure Chapter 12 Sec 12.1 - 12.7 Chapter 12 Sec 12.1 - 12.7

2. Review… Chemical bonds involve electrons Specifically, valence electrons (outer s and p orbitals) These electrons are transferred or shared in a molecule

3. Using Electronegativity: Large ∆EN = Ionic bond Medium ∆EN = Polar Covalent bond Small ∆EN = Non-polar Covalent bond Distance between location of elements on Periodic Table corresponds closely with ∆EN.

4. Polarity Bonds (and molecules) are “polar” if there is an unequal sharing of electrons

5.  Means “Partial Charge” A  - indicates a partial negative charge (near the more electronegative atom While  + is a partial positive charge

6. Compare Types of Bonds

7. KEY CONCEPT! By transferring or sharing valence electrons… ALL bonds allow the atoms in a compound to achieve a “NOBLE GAS ELECTRON CONFIGURATION”

8. Lewis Structures Provide a way to illustrate valence electrons in a molecule Allow the prediction of Molecular Geometry and Molecular Polarity

9. Lewis Structures - Main Group Elements

10. Rules for Drawing Lewis Structures: 1.Find the sum of all valence electrons of atoms in the molecule 2.Use a pair of electrons to represent a bond between two atoms 3.Rearrange remaining electrons to satisfy octet rule (or duet rule for H)

11. For an Ionic Compound: Note that Potassium loses its valence electron to chlorine. The brackets indicate a negative charge around the chloride ion.

12. For Water:

13. Double Bonds There are times when double (or triple) bonds are needed in a molecule so that each atom is surround by an octet of electrons

14. Multiple Lewis Structures - Resonance

15. Homework Complete the two Lewis Structure Handouts

16. Chemical Bonding and Molecular Structure Chapter 12 Sec 12.8 - 12.10

17. Goals: 1.To use Lewis Structures as a way to predict the geometry of Molecules 2.Determine if molecules are polar or nonpolar

18. VSEPR Model Valence Shell Electron Pair Repulsion Model Bonds (pairs of electrons) attempt to move as far away as possible from one another in a molecule

19. This explains the Geometry of H 2 O Water is a “bent” molecule, because of the lone pairs around the central Oxygen atom

20. Various Geometry of Molecules See Examples on Next Slides (Hand-Out)

23. Polar or Non-polar Molecule? A molecule may have polar covalent bonds and not be polar overall ????????? Geometry must also be considered

24. Ammonia (NH 3 ) is polar 1.The bonds between hydrogen and nitrogen are polar covalent (∆EN =.87) 2.Pyramidal geometry of molecule points charges toward N

25. Carbon Dioxide is Non-polar Even though the bonds between carbon and oxygen are polar covalent (∆EN = 1.0), the pull of electrons is in equal and opposite directions because CO 2 is linear

26. Water is Wacky! Water has some strange properties due to its structure