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VSEPR Theory Types of e - Pairs – Bonding pairs - form bonds – Lone pairs - nonbonding electrons Lone pairs repel more strongly than bonding pairs!!! Courtesy.

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Presentation on theme: "VSEPR Theory Types of e - Pairs – Bonding pairs - form bonds – Lone pairs - nonbonding electrons Lone pairs repel more strongly than bonding pairs!!! Courtesy."— Presentation transcript:

1 VSEPR Theory Types of e - Pairs – Bonding pairs - form bonds – Lone pairs - nonbonding electrons Lone pairs repel more strongly than bonding pairs!!! Courtesy Christy Johannesson

2 VSEPR Theory Lone pairs reduce the bond angle between atoms. Bond Angle Courtesy Christy Johannesson

3 Draw the Lewis Diagram. Tally up e - pairs on central atom. – double/triple bonds = ONE pair Shape is determined by the # of bonding pairs and lone pairs. Determining Molecular Shape Courtesy Christy Johannesson

4 Common Molecular Shapes 2 total 2 bond 0 lone LINEAR 180° BeH 2 Courtesy Christy Johannesson BBA

5 3 total 3 bond 0 lone TRIGONAL PLANAR 120° BF 3 Common Molecular Shapes Courtesy Christy Johannesson B B A B

6 Common Molecular Shapes 3 total 2 bond 1 lone BENT <120° SO 2 Courtesy Christy Johannesson

7 4 total 4 bond 0 lone TETRAHEDRAL 109.5° CH 4 Common Molecular Shapes Courtesy Christy Johannesson B A B B B

8 4 total 3 bond 1 lone TRIGONAL PYRAMIDAL 107° NH 3 Common Molecular Shapes Courtesy Christy Johannesson

9 4 total 2 bond 2 lone BENT 104.5° H2OH2O Common Molecular Shapes Courtesy Christy Johannesson

10 PF 3 4 total 3 bond 1 lone TRIGONAL PYRAMIDAL 107° F P F FExamples Courtesy Christy Johannesson

11 CO 2 O C O 2 total 2 bond 0 lone LINEAR 180° Examples Courtesy Christy Johannesson

12 molecular formula structural formula molecular shape ball-and-stick model CH 4 C H H HH H H H H o C tetrahedron tetrahedral shape of methane C H H H H

13 Methane & Carbon Tetrachloride molecular formula structural formula molecular shape ball-and-stick model CH 4 C H H HH H H H H o C CCl 4 space-filling model C Cl

14 Molecular Geometry H H H H o C Linear Trigonal planar Tetrahedral Trigonal pyramidal Bent o o o H 2 O CH 4 AsCl 3 AsF 5 BeH 2 BF 3 CO o

15 C o H H H H N 107 o H H H.. O o H H.. CH 4, methaneNH 3, ammoniaH 2 O, water.. O O O lone pair electrons O OO O 3, ozone

16 Molecular Shapes Three atoms (AB 2 ) Linear (180 o ) Bent BBA linear Four atoms (AB 3 ) Trigonal planar (120 o ) Trigonal pyramidal T-shaped B B A B trigonal planar Five atoms (AB 4 ) Tetrahedral ( o ) Square planar Seesaw B A B B B tetrahedral Bailar, Moeller, Kleinberg, Guss, Castellion, Metz, Chemistry, 1984, page 313.

17 Bonding and Shape of Molecules Number of Bonds Number of Unshared Pairs ShapeExamples Linear Trigonal planar Tetrahedral Pyramidal Bent BeCl 2 BF 3 CH 4, SiCl 4 NH 3, PCl 3 H 2 O, H 2 S, SCl 2 -Be- B C N : O : : Covalent Structure

18 Molecular Shapes AB 2 Linear AB 3 Trigonal planar AB 4 Tetrahedral AB 5 Trigonal bipyramidal AB 6 Octahedral AB 3 E Angular or Bent AB 3 E Trigonal pyramidal AB 3 E 2 Angular or Bent AB 4 E Irregular tetrahedral (see saw) AB 3 E 2 T-shaped AB 2 E 3 Linear AB 6 E Square pyramidal AB 5 E 2 Square planar

19 The VSEPR Model OO C Linear The Shapes of Some Simple AB n Molecules Bent OO S O Trigonal planar Trigonal pyramidal SF 6.. OO S SO 2.. F F F N Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page 305

20 Molecular Shapes AB 2 Linear AB 3 Trigonal planar AB 2 E Angular or Bent AB 4 Tetrahedral AB 3 E Trigonal pyramidal AB 2 E 2 Angular or Bent

21 Geometry of Covalent Molecules AB n, and AB n E m AB 2 AB 2 E AB 2 E 2 AB 2 E 3 AB 3 AB 3 E AB 3 E 2 AB 4 AB 4 E AB 4 E 2 AB 5 AB 5 E AB Linear Trigonal planar Tetrahedral Trigonal bipyramidal Trigonal planar Tetrahedral Triangular bipyramidal Tetrahedral Triangular bipyramidal Octahedral Triangular bipyramidal Octahedral Linear Angular, or bent Linear Trigonal planar Triangular pyramidal T-shaped Tetrahedral Irregular tetrahedral (or “see-saw”) Square planar Triangular bipyramidal Square pyramidal Octahedral CdBr 2 SnCl 2, PbI 2 OH 2, OF 2, SCl 2, TeI 2 XeF 2 BCl 3, BF 3, GaI 3 NH 3, NF 3, PCl 3, AsBr 3 ClF 3, BrF 3 CH 4, SiCl 4, SnBr 4, ZrI 4 SF 4, SeCl 4, TeBr 4 XeF 4 PF 5, PCl 5 (g), SbF 5 ClF 3, BrF 3, IF 5 SF 6, SeF 6, Te(OH) 6, MoF 6 Type Formula Shared Electron Pairs Unshared Electron Pairs Ideal Geometry Observed Molecular ShapeExamples Bailar, Moeller, Kleinberg, Guss, Castellion, Metz, Chemistry, 1984, page 317.

22 Electron-Domain Geometries Number of Electron Domains Arrangement of Electron Domains Electron-Domain Geometry Predicted Bond Angles Linear Trigonal planar Tetrahedral 180 o 120 o o B B A B B A B B B BBA

23 Number of electron domains Electron-domain geometry Predicted bond angles Tetrahedral Trigonal planar Tetrahedral o 120 o o CCOHH H HO 434 Acetic Acid, CH 3 COOH Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page 314 Hybridization of central atomsp 3 sp 2 none

24 Be H H BeH 2 s p First, the formation of BeH 2 using pure s and p orbitals. The formation of BeH 2 using hybridized orbitals. atomic orbitals Be sp H H sp atomic orbitals hybrid orbitals No overlap = no bond! spp Be HH All hybridized bonds have equal strength and have orbitals with identical energies. BeH 2 Be Be = 1s 2 2s 2

25 Hybrid Orbitals Ground-state Be atom 1s1s2s2s2p2p1s1s2s2s2p2p Be atom with one electron “promoted” s pxpx pypy pzpz sp hybrid orbitals Energy hybridize s orbital p orbital two sp hybrid orbitals sp hybrid orbitals shown together (large lobes only) 1s1ssp2p2p Be atom of BeH 2 orbital diagram HH Be n = 1 n = 2

26 Hybrid Orbitals 2s2s2p2p Ground-state B atom s pxpx pypy pzpz Energy sp 2 2p2p B atom of BH 3 orbital diagram hybridize s orbital 2s2s2p2p B atom with one electron “promoted” sp 2 hybrid orbitals p orbitals sp 2 hybrid orbitals shown together (large lobes only) three sp s hybrid orbitals H H H B

27 s pxpx pypy pzpz Carbon 1s 2 2s 2 2p 2 Carbon could only make two bonds if no hybridization occurs. However, carbon can make four equivalent bonds. sp 3 hybrid orbitals Energy sp 3 C atom of CH 4 orbital diagram B A B B B Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page 321

28 Hybridization Involving d Orbitals 3s 3p 3d promote five sp 3 d orbitals 3d3d F F F P F F A BeBe BeBe BeBe BaBa BaBa Trigonal bipyramidal hybridize degenerate orbitals (all EQUAL) unhybridized P atom P = [Ne]3s 2 3p 3 vacant d orbitals

29 Multiple Bonds 2s 2p 2s 2p sp 2 2p promotehybridize CC H HH H C 2 H 4, ethene one  bond and one  bond H H C C H H      H H C C H H Two lobes of one  bond Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page

30 Multiple Bonds 2s 2p 2s 2p sp 2 2p promotehybridize CC H HH H C 2 H 4, ethene one  bond and one  bond H H C C H H      H H C C H H Two lobes of one  bond Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page CC H H sp 2 H H pp pp

31  bond Internuclear axis pp


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