VSEPR Theory l Types of e Pairs Bonding

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VSEPR Theory l Types of e- Pairs – Bonding pairs - form bonds –

VSEPR Theory l Types of e- Pairs – Bonding pairs - form bonds – Lone pairs - nonbonding electrons Lone pairs repel more strongly than bonding pairs!!! Courtesy Christy Johannesson www. nisd. net/communicationsarts/pages/chem

l Lone VSEPR Theory pairs reduce the bond angle between atoms. Bond Angle Courtesy

l Lone VSEPR Theory pairs reduce the bond angle between atoms. Bond Angle Courtesy Christy Johannesson www. nisd. net/communicationsarts/pages/chem

Determining Molecular Shape l Draw the Lewis Diagram. l Tally up e- pairs on

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

Common Molecular Shapes 2 total 2 bond 0 lone B A B Be. H

Common Molecular Shapes 2 total 2 bond 0 lone B A B Be. H 2 LINEAR 180° Courtesy Christy Johannesson www. nisd. net/communicationsarts/pages/chem

Common Molecular Shapes 3 total 3 bond 0 lone B A B B BF

Common Molecular Shapes 3 total 3 bond 0 lone B A B B BF 3 TRIGONAL PLANAR 120° Courtesy Christy Johannesson www. nisd. net/communicationsarts/pages/chem

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

Common Molecular Shapes 3 total 2 bond 1 lone SO 2 BENT <120° Courtesy Christy Johannesson www. nisd. net/communicationsarts/pages/chem

Common Molecular Shapes B 4 total 4 bond 0 lone A B B B

Common Molecular Shapes B 4 total 4 bond 0 lone A B B B CH 4 TETRAHEDRAL 109. 5° Courtesy Christy Johannesson www. nisd. net/communicationsarts/pages/chem

Common Molecular Shapes 4 total 3 bond 1 lone NH 3 TRIGONAL PYRAMIDAL 107°

Common Molecular Shapes 4 total 3 bond 1 lone NH 3 TRIGONAL PYRAMIDAL 107° Courtesy Christy Johannesson www. nisd. net/communicationsarts/pages/chem

Common Molecular Shapes 4 total 2 bond 2 lone H 2 O BENT 104.

Common Molecular Shapes 4 total 2 bond 2 lone H 2 O BENT 104. 5° Courtesy Christy Johannesson www. nisd. net/communicationsarts/pages/chem

l PF 3 4 total 3 bond 1 lone Examples F P F F

l PF 3 4 total 3 bond 1 lone Examples F P F F TRIGONAL PYRAMIDAL 107° Courtesy Christy Johannesson www. nisd. net/communicationsarts/pages/chem

l CO 2 2 total 2 bond 0 lone Examples O C O LINEAR

l CO 2 2 total 2 bond 0 lone Examples O C O LINEAR 180° Courtesy Christy Johannesson www. nisd. net/communicationsarts/pages/chem

H H CH 4 H C H H molecular formula structural formula H C

H H CH 4 H C H H molecular formula structural formula H C 109. 5 o H H molecular shape H C H H H tetrahedral shape of methane tetrahedron ball-and-stick model

Methane & Carbon Tetrachloride molecular formula structural formula molecular shape H CH 4 H

Methane & Carbon Tetrachloride molecular formula structural formula molecular shape H CH 4 H C ball-and-stick model H H C 109. 5 o H H Cl CCl 4 Cl Cl space-filling model

Molecular Geometry 180 o H H Trigonal planar Linear C 109. 5 o H

Molecular Geometry 180 o H H Trigonal planar Linear C 109. 5 o H H Tetrahedral 107. 3 o Trigonal pyramidal 104. 5 o Bent H 2 O CH 4 As. Cl 3 As. F 5 Be. H 2 BF 3 CO 2

. . C N O H 109. 5 o H H CH 4, methane

. . C N O H 109. 5 o H H CH 4, methane lone pair electrons H 107 o H . . H H H NH 3, ammonia 104. 5 o H 2 O, water . . O O O 3, ozone H O O

Molecular Shapes Three atoms (AB 2) Four atoms (AB 3) • Linear (180 o)

Molecular Shapes Three atoms (AB 2) Four atoms (AB 3) • Linear (180 o) • Bent B A linear B B • Trigonal planar (120 o) • Trigonal pyramidal • T-shaped B A B trigonal planar B Five atoms (AB 4) • Tetrahedral (109. 47 o) • Square planar • Seesaw tetrahedral A B Bailar, Moeller, Kleinberg, Guss, Castellion, Metz, Chemistry, 1984, page 313.

Bonding and Shape of Molecules Number of Unshared Pairs Covalent Structure Shape Examples -Be-

Bonding and Shape of Molecules Number of Unshared Pairs Covalent Structure Shape Examples -Be- Linear Be. Cl 2 Trigonal planar BF 3 2 0 3 0 4 0 C Tetrahedral CH 4, Si. Cl 4 3 1 : Number of Bonds Pyramidal NH 3, PCl 3 2 2 Bent H 2 O, H 2 S, SCl 2 B : N O:

Molecular Shapes AB 2 Linear AB 3 Trigonal planar AB 3 E Angular or

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

The VSEPR Model The Shapes of Some Simple ABn Molecules Linear O C Bent

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

Molecular Shapes AB 2 Linear AB 3 Trigonal planar AB 2 E Angular or

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

Geometry of Covalent Molecules ABn, and ABn. Em Type Formula Shared Electron Pairs Unshared

Geometry of Covalent Molecules ABn, and ABn. Em Type Formula Shared Electron Pairs Unshared Electron Pairs AB 2 E 2 AB 2 E 3 AB 3 E 2 2 3 3 0 1 2 3 0 1 Linear Trigonal planar Tetrahedral Trigonal bipyramidal Trigonal planar Tetrahedral Linear Angular, or bent Linear Trigonal planar Triangular pyramidal Cd. Br 2 Sn. Cl 2, Pb. I 2 OH 2, OF 2, SCl 2, Te. I 2 Xe. F 2 BCl 3, BF 3, Ga. I 3 NH 3, NF 3, PCl 3, As. Br 3 AB 3 E 2 AB 4 3 4 2 0 Triangular bipyramidal Tetrahedral T-shaped Tetrahedral Cl. F 3, Br. F 3 CH 4, Si. Cl 4, Sn. Br 4, Zr. I 4 AB 4 E 4 1 Triangular bipyramidal SF 4, Se. Cl 4, Te. Br 4 AB 4 E 2 AB 5 4 5 2 0 Octahedral Triangular bipyramidal Irregular tetrahedral (or “see-saw”) Square planar Triangular bipyramidal AB 5 E AB 6 5 6 1 0 Octahedral Square pyramidal Octahedral Cl. F 3, Br. F 3, IF 5 SF 6, Se. F 6, Te(OH)6, Mo. F 6 Ideal Geometry Bailar, Moeller, Kleinberg, Guss, Castellion, Metz, Chemistry, 1984, page 317. Observed Molecular Shape Examples Xe. F 4 PF 5, PCl 5(g), Sb. F 5

Electron-Domain Geometries Number of Electron Domains 2 Arrangement of Electron Domains B A B

Electron-Domain Geometries Number of Electron Domains 2 Arrangement of Electron Domains B A B Electron-Domain Geometry Predicted Bond Angles Linear 180 o Trigonal planar 120 o Tetrahedral 109. 5 o B A 3 B B B 4 A B B B

Acetic Acid, CH 3 COOH H H O C C O 3 4 H

Acetic Acid, CH 3 COOH H H O C C O 3 4 H H Number of electron domains Electron-domain geometry Predicted bond angles Hybridization of central atom Brown, Le. May, Bursten, Chemistry The Central Science, 2000, page 314 4 Tetrahedral Trigonal planar Tetrahedral 109. 5 o 120 o 109. 5 o sp 3 sp 2 none

First, the formation of Be. H 2 using pure s and p orbitals. Be

First, the formation of Be. H 2 using pure s and p orbitals. Be = 1 s 22 s 2 H Be. H 2 Be s p atomic orbitals H No overlap = no bond! atomic orbitals The formation of Be. H 2 using hybridized orbitals. atomic orbitals H Be s Be H p H hybrid orbitals H Be s p Be. H 2 Be sp p All hybridized bonds have equal strength and have orbitals with identical energies.

Hybrid Orbitals Ground-state Be atom 1 s 2 s 2 p Be atom with

Hybrid Orbitals Ground-state Be atom 1 s 2 s 2 p Be atom with one electron “promoted” 1 s 2 s 2 p Energy hybrid orbitals px py pz n=2 sp s 1 s sp 2 p Be atom of Be. H 2 orbital diagram n=1 hybridize s orbital H p orbital two sp hybrid orbitals shown together (large lobes only) Be H

Hybrid Orbitals Ground-state B atom 2 s 2 p B atom with one electron

Hybrid Orbitals Ground-state B atom 2 s 2 p B atom with one electron “promoted” 2 s 2 p Energy hybrid orbitals px py pz sp 2 s 2 p B atom of BH 3 orbital diagram H hybridize B s orbital H p orbitals three sps hybrid orbitals sp 2 hybrid orbitals shown together (large lobes only) H

Carbon 1 s 22 p 2 Carbon could only make two bonds if no

Carbon 1 s 22 p 2 Carbon could only make two bonds if no hybridization occurs. However, carbon can make four equivalent bonds. B A B B Energy hybrid orbitals px py B pz s Brown, Le. May, Bursten, Chemistry The Central Science, 2000, page 321 sp 3 C atom of CH 4 orbital diagram

Hybridization Involving d Orbitals promote 3 s 3 p 3 d unhybridized P atom

Hybridization Involving d Orbitals promote 3 s 3 p 3 d unhybridized P atom P = [Ne]3 s 23 p 3 3 s hybridize Ba Be F F five sp 3 d orbitals A 3 d Be F F 3 d vacant d orbitals F P 3 p Be Ba Trigonal bipyramidal degenerate orbitals (all EQUAL)

Multiple Bonds hybridize promote 2 s 2 p sp 2 2 p C 2

Multiple Bonds hybridize promote 2 s 2 p sp 2 2 p C 2 H 4, ethene H H C C H H one s bond and one p bond H H s C s H s C H C s C H H Brown, Le. May, Bursten, Chemistry The Central Science, 2000, page 325 -326 Two lobes of one p bond H

C C Multiple Bonds hybridize promote 2 s 2 p sp 2 C 2

C C Multiple Bonds hybridize promote 2 s 2 p sp 2 C 2 H 4, ethene HH H p sp 2 C 2 p HH p sp 2 C sp 2 H sp 2 p p one s bond and one p bond H H s C s H s C H C s C H H Brown, Le. May, Bursten, Chemistry The Central Science, 2000, page 325 -326 Two lobes of one p bond H HH

p bond Internuclear axis p p

p bond Internuclear axis p p