1. Valence Bond Theory

2. Valence Bonding Theory  Incorporates atomic orbitals of atoms, use of quantum theory  Dealing ONLY with orbitals involved in a covalent bond  Electron clouds of individual atoms OVERLAP when atoms form chemical bond

4. Valence Bonding Theory (cont.)  Covalent bond formation involves 2 electrons of opposite spins paired in an overlap of atomic orbitals with high electron density (p. 403)  Strong chemical bonds with more atomic overlap  Optimal orbital overlap---gives maximum bond strength

5. Key Points to Valence Bond Theory 1)Electrons generally like to stay in their normal orbitals (as if in isolated atom). 2)Electrons involved in a chemical bond hang out in an atomic orbital overlap. 3)The orientation of the atomic orbitals of the central atom determine its molecular geometry 4)Atomic orbitals with more than one axis (p orbital)– maximum overlap found when imaginary line connecting the atoms passes through the maximum overlap.

6. Hybridization

7.  Electron configuration of Carbon (show only valence electrons)

8. **Atoms in a chemical bond do NOT have the same orbitals as in isolation **

9. Hybridization—General  Combines/Mixes atomic orbitals  Not an actual process, a method of visualizing and explaining molecular structure  Hybrid orbitals—  Mix of 2 types of orbitals

10. Back to Carbon  Combine/mix together “s ” and “p” orbitals  Result is 4 orbitals with same shape and energy

12. Hybridization—General (cont.)  Applies mostly to central atoms  # hybrid orbitals = # of combined orbitals  Hybrid orbitals can interact/overlap with regular or hybrid orbitals  Hybrid orbitals have different shapes and orientations from regular orbitals

13. Hybrid Orbitals 1)sp 3 hybrid orbitals  Mixture of 1 s orbital and 3 p orbitals  Results in 4 hybrid orbitals  Tetrahedral structure, 109.5° bond angle Ex. CH 4 —C NH 3 ---N

16. Hybrid Orbitals 2) sp 2 hybrid orbitals  Seen a lot with double bonds  Mixture of 1 s orbital and 2 p orbitals  results in 3 hybrid orbitals  Trigonal planar structure, 120° bond angle Ex. BF 3

18. Hybrid Orbitals 3) sp hybrid orbitals  Seen a lot with triple bonds  Mixture of 1 s orbital and 1 p orbital  Results in 2 hybrid orbitals, 2 empty p orbitals  Linear structure, 180° bond angle Ex. BeCl 2

21. How do we discuss hybridization????  Focus on central atom  Each atomic orbital results in a hybrid orbital in chemical bond  ALL hybrid orbitals have electrons (lone or bonded pair)  Hybrid orbital orientation = electron group geometry 1)Determine electron group geometry 2)Find appropriate hybridization 3)Describe how the orbitals overlap to give molecular geometry

22. Electron Group Electron Group Geometry Hybridizati on 2 Linear sp 3Trigonal planar sp 2 4Tetrahedralsp 3

23. Ex. 1 Determine the hybridization of the central atom in….. H3O+H3O+

24. Ex. 2 Determine the hybridization of the central atom in…..  NH 3

25. Ex. 3 Determine the hybridization of the central atom in…..  CO 2

26. Ex. 4 Determine the hybridization of the central atom in….. O2O2

27. Homework  Molecular Geometry (p. 427 #21, 23, 25, 27)  Hybridization (Read pp. 402-408, p. 428 #45-46)