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Chapter 9 Covalent Bonding: Orbitals

Chapter 9 Covalent Bonding: Orbitals. Hybridization The mixing of atomic orbitals to form special orbitals for bonding. The atoms are responding as needed to give the minimum energy for the molecule. The Valence Orbitals on a Free Carbon Atom: 2s , 2p x , 2p y , and 2p z.

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Chapter 9 Covalent Bonding: Orbitals

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  1. Chapter 9Covalent Bonding: Orbitals Hybridization • The mixing of atomic orbitals to form special orbitals for bonding. • The atoms are responding as needed to give the minimum energyfor the molecule.

  2. The Valence Orbitals on a Free Carbon Atom: 2s, 2px, 2py, and 2pz

  3. The Formation of sp3 Hybrid Orbitals

  4. An Energy-Level Diagram Showing the Formation of Four sp3 Orbitals

  5. Tetrahedral Set of Four sp3 Orbitals

  6. The Nitrogen Atom in Ammonia is sp3 Hybridized

  7. sp3 Hybridization The experimentally known structure of CH4 molecule can be explained if we assume that the carbon atom adopts a special set of atomic orbitals. These new orbital are obtained by combining the 2s and the three 2p orbitals of the carbon atom to produce four identically shaped orbital that are oriented toward the corners of a tetrahedron and are used to bond to the hydrogen atoms. Whenever a set of equivalent tetrahedral atomic orbitals is required by an atom, this model assumes that the atom adopts a set of sp3 orbitals; the atom becomes sp3 hybridized.

  8. The Hybridization of the s, px, and py Atomic Orbitals

  9. An Orbital Energy-Level Diagram for sp2 Hybridization

  10. A sigma () bondcenters along the internuclear axis. • A pi () bondoccupies the space above and below the internuclear axis.

  11. An sp2 Hybridized C Atom

  12. The s Bonds in Ethylene

  13. Sigma and Pi Bonding

  14. The Orbitals for C2H4

  15. When One s Orbital and One p Orbital are Hybridized, a Set of Two sp Orbitals Oriented at 180 Degrees Results

  16. The Hybrid Orbitals in the CO2 Molecule

  17. The Orbital Energy-Level Diagram for the Formation of sp Hybrid Orbitals on Carbon

  18. The Orbitals of an sp Hybridized Carbon Atom

  19. The Orbital Arrangement for an sp2 Hybridized Oxygen Atom

  20. The Orbitals for CO2

  21. The Orbitals for N2

  22. A Set of dsp3 Hybrid Orbitals on a Phosphorus Atom

  23. An Octahedral Set of d2sp3 Orbitals on a Sulfur Atom

  24. The Relationship of the Number of Effective Pairs, Their Spatial Arrangement, and the Hybrid Orbital Set Required

  25. The Localized Electron Model Three Steps: • Draw the Lewis structure(s) • Determine the arrangement of electron pairs (VSEPR model). • Specify the necessary hybrid orbitals.

  26. Molecular Orbitals (MO) • Analagous to atomic orbitals for atoms, MOs are the quantum mechanical solutions to the organization of valence electrons in molecules. • Molecular orbitals have many of the same characteristics as atomic orbitals, such as they can hold two electrons with opposite spins and the square of the molecular orbital wave function indicates electron probability.

  27. The Combination of Hydrogen 1s Atomic Orbitals to Form Molecular Orbitals

  28. The Molecular Orbitals for H2

  29. Types of MOs • bonding: lower in energy than the atomic orbitals from which it is composed. Electrons in this type of orbital will favor the molecule. • antibonding: higher in energy than the atomic orbitals from which it is composed. Electrons in this type of orbital will favor the separated atoms.

  30. Bonding and Antibonding Molecular Orbitals (MOs)

  31. The Molecular Orbital Energy-Level Diagram for the H2 Molecule

  32. The Molecular Orbital Energy-Level Diagram for the H2- Ion

  33. Bond Order (BO) • Difference between the number of bonding electrons and number of antibonding electrons divided by two. • Bonds order is an indication of bond strength. Large bond order means greater bond strength.

  34. The Molecular Orbital Energy-Level Diagram for the He2 Molecule

  35. Bonding in Homonuclear Diatomic Molecules In order to participate in MOs, atomic orbitals must overlap in space. (Therefore, only valence orbitals of atoms contribute significantly to MOs.)

  36. The Relative Sizes of the Lithium 1s and 2s Atomic Orbitals

  37. The Molecular Orbital Energy-Level Diagram for the Li2 Molecule

  38. The Molecular Orbitals from p Atomic Orbitals

  39. The Expected Molecular Orbital Energy-Level Diagram Resulting from the Combination of the 2p Orbitals on Two Boron Atoms

  40. The Expected Molecular Orbital Energy-Level Diagram for the B2 Molecule

  41. Paramagnetism • unpaired electrons • attracted to induced magnetic field • much stronger than diamagnetism

  42. Diamagnetism • paired electrons • repelled from induced magnetic field • much weaker than paramagnetism

  43. Diagram of the Kind of Apparatus Used to Measure the Paramagnetism of a Sample

  44. The Correct Molecular Orbital Energy-Level Diagram for the B2 Molecule

  45. Molecular Orbital Summary of Second Row Diatomics

  46. Outcomes of MO Model • As bond orderincreases, bond energy increases and bond length decreases. • Bond order is not absolutely associated with a particular bond energy. • N2 has a triple bond, and a correspondingly high bond energy. • O2 is paramagnetic. This is predicted by the MO model, not by the LE model, which predicts diamagnetism.

  47. Combining LE and MO Models •  bonds can be described as being localized. •  bonding must be treated as being delocalized.

  48. The Resonance Structures for O3 and NO3-

  49. A Benzene Ring

  50. The Sigma System for Benzene

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