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Similar to Tang 06 valence bond theory and hybridization
Tang 06 valence bond theory and hybridization
- 1. VALENCE BOND THEORY& HYBRIDIZATION
- 2. VALENCE BOND THEORY LinusPauling explain how atoms come together and form molecules with the Valence Bond Theory: – A covalent bond forms when two half-filled orbitals overlap to produce a new combined orbital containing two electrons of opposite spin. – This overlapping results in a decrease in the energy of the atoms forming the bond – The shared electron pair is most likely to be found in the space between the two nuclei of the atoms forming the bonds.
- 3. Ex. H2 H H 1s1s Overlappingof the 1s orbitals Covalent Bond H-H 1s The newly combined orbital will contain an electron pair with opposite spin just like a filled atomic orbital VALENCE BOND THEORY
- 4. In hydrogen fluoridethe 1s orbital of the H will overlap with the half-filled 2p orbital of the F forming a covalent bond H F 2p1s + Overlapping of the1s and 2p orbitals + Covalent Bond H-F + VALENCE BOND THEORY Ex. HF
- 5. According to theValence Bond Theory, how many bonds can carbon form? But, how many bonds does carbon really form? VALENCE BOND THEORY 4
- 6. Example: Methane (CH4) CHH H H C 2p 2s 1s Lewis dot diagram: Carbon makes 4 bonds Energy level diagram of carbon: How can 3 orbitals form 4 bonds? HYBRIDIZATION
- 7. C 2p 2s 1s The orbitals canhybridize with each other to form 4 bonds: 2s and 2p orbitals hybridize Four sp3 hybridized orbitals are formed sp3 sp3 sp3 sp3 Example: Methane (CH4) HYBRIDIZATION
- 8. HYBRIDIZATION THEORY • TheHybridization Theory provides a description of the process involving the combination of atomic orbitals to create new bonding orbitals • A hybrid orbital is created by combining at least two different orbitals to produce maximum bonding opportunities • Hybrid orbitals are created through the promotion of electrons One of carbons 2s electrons is promoted to the empty 2p orbital The result produces 4 unpaired electrons for bonding
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- 12. How do orbitalshybridize? CC 2p 2s 1s C 2p 2s 1s Hybridized orbitals Hybridized orbitals are wider than non-hybridized orbitals Example: Methane (CH4) HYBRIDIZATION
- 13. The 4 bondsfits with the accepted 3D structure of CH4 Example: Methane (CH4) HYBRIDIZATION
- 14. What really happens? Thenucleus of a hydrogen atom attracts one of the lower-energy valence electrons on carbon. This causes an excitation, moving a 2s electron into a 2p orbital. This, however, increases the attraction of the carbon nucleus on the valence electrons (since the nucleus is slightly less shielded) C 2p 2s 1s H nucleus Example: Methane (CH4) HYBRIDIZATION
- 15. What really happens? C 2p 2s 1s sp3hybridized orbitals 4 hydrogen atoms bond, thus filling every orbital to make a stable product Final product: C H H H H Example: Methane (CH4) HYBRIDIZATION
- 16. These are sigmabonds (σ bonds) - a sigma bond is a single, covalent bond - example: sigma bond Example: Methane (CH4) Overlapping of the1s and 2p orbitals + - results from end-to-end overlap HYBRIDIZATION
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- 18. Example: Ethene (C2H4) Structure: sigmabond pi bond -Double bonds are composed of a sigma bond (end-to-end) and a pi (π) bond (side-by-side overlap) -pi are covalent bonds, but are weaker than sigma bonds HYBRIDIZATION
- 19. Example: Ethene (C2H4) C 2p 2s 1s Theorbitals will hybridize to make 3 sigma bonds + 1 pi bond: One 2s and two 2p orbitals hybridize sp2 sp2 sp2 (not hybridized) HYBRIDIZATION
- 20. Example: Ethene (C2H4) Howdo orbitals hybridize? CC 2p 2s 1s C 2p 2s 1s Hybridized orbitals HYBRIDIZATION
- 21. Example: Ethene (C2H4) Howdo the carbons bond in ethene? C C H H H H Two lobes form one π bond The π bond is symmetrical and above the plane and prevents rotation around the axis between the carbon atoms HYBRIDIZATION
- 22. Example: Ethene (C2H4) Todraw it more simply… C C H H H H HYBRIDIZATION
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- 24. Example: Ethyne (C2H2) πbond σ bond π bond Triple bonds are composed of a sigma bond (end-to-end) and two pi (π) bonds (side-by-side) HYBRIDIZATION
- 25. Example: Ethyne (C2H2) C 2p 2s 1s Theorbitals will hybridize to make 2 sigma bonds + 2 pi bonds: One 2s and one 2p orbital hybridizes sp sp (non-hybridized p orbitals) HYBRIDIZATION
- 26. Example: Ethyne (C2H2) CCH H π bond π bond σ bond HYBRIDIZATION
- 27. Example: Ethyne (C2H2) CCH H 1s sp sp sp sp p p p p HYBRIDIZATION
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- 30. Bond Type HybridsPure Bond Distribution Single 4 sp3 0 Hybrids make 4 σ bonds Double 3 sp2 1 p π bond is made from pure orbital, σ is made from a hybrid Triple 2 sp 2 p π bonds are made from both pure orbitals, σ is made from a hybrid http://pages.towson.edu/ladon/carbon.html HYBRIDIZATION Summary: Hybridization of Carbon to Make Multiple Bonds
- 31. HYBRIDIZATION Hybridization theory explainshow boron can make 3 bonds (ex. BCl3) B 2p 2s 1s One 2s and two 2p orbital hybridizes sp2 sp2 (non-hybridized p orbital)sp2
- 32. HYBRIDIZATION Hybridization theory explainshow boron can make 3 bonds (ex. BCl3)
- 33. HYBRIDIZATION Hybridization theory explainshow beryllium can make 2 bonds even though its 2s orbital is full (ex. BeCl2) One electron from 2s is promoted to 2p to form two new hybridized orbitals
- 34. HYBRIDIZATION Hybridization theory explainshow beryllium can make 2 bonds even though its 2s orbital is full (ex. BeCl2)
- 35. HYBRIDIZATION Hybridization theory explainshow sulfur can make 6 bonds (ex. SF6) 1 electron from 3s is promoted to 3p, and 2 electrons from 3p are promoted to 3d 6 sp3d2 hybridized orbitals are formed
- 36. HYBRIDIZATION 1 electron from3s is promoted to 3p, and 2 electrons from 3p are promoted to 3d
- 37. HYBRIDIZATION Hybridization theory explainshow sulfur can make 6 bonds (ex. SF6)
- 38. HYBRIDIZATION Hybridization theory explainshow phosphorus can have a valence of +5 (ex. PCl5) One 3s electron is promoted to 3d, forming 5 hybridized orbitals
- 39. HYBRIDIZATION Hybridization theory explainshow phosphorus can have a valence of +5 (ex. PCl5) One 3s electron is promoted to 3d, forming 5 hybridized orbitals
- 40. HYBRIDIZATION Hybridization theory explainshow phosphorus can have a valence of +5 (ex. PCl5)
- 41. HYBRIDIZATION Summary Number of groups attachedto central atom Hybridization Example Two groups sp BeCl2 Three groups sp2 BCl3 Four groups sp3 CH4 Five groups sp3d PCl5 Six groups sp3d2 SF6
- 42. Homework 1. Use thevalence bond model or hybridization theory to show the bonding in the following molecules: BeH2, BH3, CCl4, PCl5, SF6 2. Page 238 # 1 – 5, 7, 8, 10 HYBRIDIZATION