1. © Prentice Hall 2001Chapter 11 Atomic Orbitals We cannot know the exact course of electrons as they orbit the nucleus - Heisenberg uncertainty principle The wave functions, however, give approximate shapes to orbitals s orbitals are spherical p orbitals are shaped like dumbbells

2. © Prentice Hall 2001Chapter 12 1s and 2s Orbitals

3. © Prentice Hall 2001Chapter 13 2p Orbitals

4. © Prentice Hall 2001Chapter 14 Molecular Orbitals for Hydrogen Allow the 1s orbital of one hydrogen atom to overlap with the 1s orbital of a neighboring hydrogen atom

5. © Prentice Hall 2001Chapter 15 Molecular Orbitals for Hydrogen The electrons in a molecule are everywhere The shape we draw is only the surface enclosing a certain percentage of the electron density Highest electron density is directly between the hydrogen nuclei

6. © Prentice Hall 2001Chapter 16 Molecular Orbitals for Hydrogen The result defines a  (sigma) bond between the atoms

7. © Prentice Hall 2001Chapter 17 Molecular Orbitals for Hydrogen

8. © Prentice Hall 2001Chapter 18 Molecular Orbital From p Electrons Molecular orbitals also can be formed from p orbitals

9. © Prentice Hall 2001Chapter 19 End-On Overlap of p Orbitals Leads to  Bonding

10. © Prentice Hall 2001Chapter 110 Side-by-Side Overlap of p Orbitals Leads to  Bonding

11. © Prentice Hall 2001Chapter 111 Hybrid Orbitals Methane, CH 4, has four equivalent carbon-hydrogen bonds

12. © Prentice Hall 2001Chapter 112 Hybrid Orbitals Ground state for carbon is 1s 2 2s 2 2p 2 There are only two partially filled orbitals that are capable of participating in bonding How can four bonds be made? Problem can be solved by promoting one 2s electron to an empty 2p orbital pxpypzspxpypzs pxpypzspxpypzs

13. © Prentice Hall 2001Chapter 113 Hybridization If four bonds were formed from the 2s2p2p2p configuration, we might expect three of the bonds to be at exactly 90 o and the other at any angle

14. © Prentice Hall 2001Chapter 114 Hybridization Theory: Mix the 2s orbital with the three 2p orbitals to form four equivalent hybrid orbitals

15. © Prentice Hall 2001Chapter 115 Hybridization - Tetrahedral Carbon In methane, the four sp 3 hybrid orbitals overlap with s orbitals from four hydrogen atoms to form four equivalent carbon-hydrogen bonds A carbon atom that has sp 3 hybrid orbitals is called a tetrahedral carbon

16. © Prentice Hall 2001Chapter 116 Hybridization - Tetrahedral Carbon The sp 3 hybrid orbital on carbon also can bond with another sp 3 hybrid orbital from a neighboring carbon to form a carbon- carbon single bond

17. © Prentice Hall 2001Chapter 117 sp 2 Hybridization in Ethene Each carbon in ethene (H 2 C=CH 2 ) is bonded to only three atoms To do this, each carbon hybridizes only three orbitals to give sp 2 hybridization

18. © Prentice Hall 2001Chapter 118 sp 2 Hybridization in Ethene

19. © Prentice Hall 2001Chapter 119 sp 2 Hybridization in Ethene The three sp 2 hybrid orbitals all lie in a plane and are oriented at angles of 120 o Such carbons are called trigonal planar carbons

20. © Prentice Hall 2001Chapter 120 sp 2 Hybridization in Ethene The carbon-carbon bond formed from the overlap of an sp 2 orbital on one carbon with an sp 2 orbital on a neighboring carbon atom results in an orbital which is cylindrically symmetric about the carbon-carbon axis

21. © Prentice Hall 2001Chapter 121 sp 2 Hybridization in Ethene A second bond is formed between the two carbon atoms via the side-by-side overlap of the remaining (un-hybridized) p orbitals Electron density accumulates above and below the carbon-carbon axis

22. © Prentice Hall 2001Chapter 122 sp 2 Hybridization in Ethene This second carbon-carbon bond is called a  bond The two p orbitals which overlap side-by-side, must be parallel to each other The four hydrogen atoms therefore must be in the same plane No rotation about a carbon-carbon double bond

23. © Prentice Hall 2001Chapter 123 sp Hybridization in Ethyne Each carbon in ethyne (HC  CH) is bonded to only two atoms To do this, each carbon hybridizes only two orbitals to give sp hybridization

24. © Prentice Hall 2001Chapter 124 sp Hybridization in Ethyne The overlap of the sp hybrid orbitals forms a  bond

25. © Prentice Hall 2001Chapter 125 sp Hybridization in Ethyne The remaining p orbitals overlap side-by- side, forming  bonds with electron density above and below the carbon- carbon axis as well as in front and in back

26. © Prentice Hall 2001Chapter 126 sp Hybridization in Ethyne The two  bonds together form a cylinder of electron density around the  bond

27. © Prentice Hall 2001Chapter 127 Summary of Orbital Hybridization