The Central Themes of VB Theory

1. The Central Themes of VB Theory Themes A set of overlapping orbitals has a maximum of two electrons that must have opposite spins. The greater the orbital overlap, the stronger (more stable) the bond. The valence atomic orbitals in a molecule are different from those in isolated atoms. There is a hybridization of atomic orbitals to form molecular orbitals.

2. Orbital overlap and spin pairing in three diatomic molecules. Hydrogen, H2 Hydrogen fluoride, HF Fluorine, F2

3. Key Points Types of Hybrid Orbitals sp sp2 sp3 sp3d sp3d2 Hybrid Orbitals The number of hybrid orbitals obtained equals the number of atomic orbitals mixed. The type of hybrid orbitals obtained varies with the types of atomic orbitals mixed.

4. The sp hybrid orbitals in gaseous BeCl2. atomic orbitals hybrid orbitals orbital box diagrams

5. The sp hybrid orbitals in gaseous BeCl2. orbital box diagrams with orbital contours

6. The sp2 hybrid orbitals in BF3.

7. The sp3 hybrid orbitals in CH4.

8. The sp3 hybrid orbitals in NH3.

9. The sp3 hybrid orbitals in H2O.

10. The sp3d hybrid orbitals in PCl5.

11. The sp3d2hybrid orbitals in SF6.

13. both C are sp3 hybridized s-sp3 overlaps to s bonds sp3-sp3 overlap to form a s bond relatively even distribution of electron density over all s bonds The s bonds in ethane(C2H6).

14. The s and p bonds in ethylene (C2H4).

15. The s and p bonds in acetylene (C2H2).

16. Contours and energies of the bonding and antibonding molecular orbitals (MOs) in H2. The bonding MO is lower in energy and the antibonding MO is higher in energy than the AOs that combined to form them.

17. 1s 1s AO of H AO of H The MO diagram for H2. Filling molecular orbitals with electrons follows the same concept as filling atomic orbitals. s*1s Energy H2 bond order = 1/2(2-0) = 1 s1s MO of H2

18. s*1s Energy 1s 1s 1s 1s s1s AO of He AO of He+ AO of He AO of He MO diagram for He2+ and He2. s*1s Energy s1s MO of He+ MO of He2 He2 bond order = 0 He2+ bond order = 1/2

19. s*2s s*2s 2s 2s 2s 2s s2s s2s Bonding in s-block homonuclear diatomic molecules. Energy Be2 Li2 Be2 bond order = 0 Li2 bond order = 1

20. Contours and energies of s and p MOs through combinations of 2p atomic orbitals.

21. Relative MO energy levels for Period 2 homonuclear diatomic molecules. without 2s-2p mixing with 2s-2p mixing MO energy levels for O2, F2, and Ne2 MO energy levels for B2, C2, and N2

22. MO occupancy and molecular properties for B2 through Ne2

23. The paramagnetic properties of O2