Molecular Geometry and Polarization

Shapes of Molecules

Valence Shell Electron Pair Repulsion Theory (VSEPR)a. Bonded electronsb. Lone Pairs

1. Linear (180o)BeH2 CO2

2. Trigonal Planar (120o)NO3

-

3. Tetrahedral (109.5o)CH4

4. Trigonal Pyramidal (~107o)NH3

5. Bent (~104.5o)H2O

OH H

SO2

6. Trigonal Bipyramid (120o, 90o)PCl5

7. Octahedral (90o)SF6

Shapes of Molecules

Ex: Multiple Bonds:N2

H2CO

HCNSO2

Shapes of Molecules

Models Activity

SO22+

SO22-

SO2

SO3

SF3-

PF4-

XeCl5+

BrF4-

Predict the molecular geometry of:

SnCl3-

O3

SeCl2

CO32-

SF4

IF5

ClF3

ICl4-

WarmUp

ClF4-

SiCl3-

SO2

SCl4

SeO3

BrCl5

BrCl3

Polar Molecules

1. Polar molecule – Overall, the electrons are attracted more to one end of an entire molecule

2. Non-Polar Molecule – The electrons are spread out evenly over the entire molecule

-/ + Partial (not full) charges

Examples:H2 H2O

CH4 H2CO

H2 H2O

CH4 H2CO

Electron Density

Polar MoleculesBeCl2

NH3

CO2

SO2

SF6

BCl3

CH2Cl2

SCO CH3F

BH2Cl PH3

CHF3 CH2F2

SO3 SO32-

NF3 CH3CHO

Hybrid Orbitals• A mixing of the atomic orbitals (s, p, d, f) of the

central atom• Electrons no longer move in the old orbitals, but

in a new pattern

BeF2

Isolated Be 1s22s2 (Note that all Be: electrons are paired)

To bond Be must unpair some electrons:

Bonded Be 1s22s12p1 •Be•

• Be is called an “sp” hybrid.• Drawings:

Isolated Be BeF2

CH4

Isolated C 1s22s22p2

Bonded C 1s22s12p3

Isolated C

Bonded C sp3

Effect of Lone Pairs

• Lone pairs do count towards hybridization• Ex: H2O

Try BF3

ExamplesCCl4

NH3

PF5

SF6

XeF4

BrF3

PH3

H2S

SF5-

SF4

CO32-

HCNBrCl3

CH4

H2SSO2

SO22-

AsCl5ClF3

KrF4

Hybrid Orbitals and Multiple Bonds

• sigma () bonds – single bonds formed by hybrid orbitals

• pi () bonds – double or triple bonds, not formed by hybrid orbitals

H HH – H C=C :N=N:

H HOne bond One bond plus One bond plus

one bond two bonds

• Consider C2H4

• Each C is sp2

• Double bond does not count toward hybridization

• Consider C2H2

• Each C is sp hybridized• Twobonds do not count toward hybridization

What is the hybridization and bonding types for H2CO? Also, what are the bond angles?

What is the hybridization and bonding types for acetonitrile (shown)? Also, what are the bond

angles?

HH - C -C=N:

H

Delocalized Bonding

• Adjacent multiple bonds can overlap.• Benzene (C6H6)

• All bond lengths are equal

Use hybrid orbital theory to explain why all the bonds in the NO3

- ion are of equal length

12 a) ~110o b) BF3 flat (no lone pair)

21. a) (lin)linb) (tetr)tr. Py c) (Trig bi)ss d) (oh)oh e) (tetr)tetr f) (lin)lin

22 a) (Tetra) Trig. Pyramid b) (Trig planar), Trig pl

c) (Tr. Bipy) T d) (Tetra) Tetra e) (Trig Bipy) lin f) (Tetra) Bent

24 a) i) Octa (sq.planar) ii) Tetrahedral iii) Trig Bipyr.(see-saw)

b) i) Two ii) O iii) Onec) S or Sed) Xe

26. a) 104.5o, 120o b) 109.5o, 120o

c) 107o, 104.5o d) 180o, 109.5o 28. 2 LP (NH2

-, ~109o), 1 LP (NH3, 107o), 0 LP (NH4+,

109o)30. a) ClO2

- (~109.5o, 2LP) NO2- (120o, 1 LP)

b) XeF2 (4 LP around the center)

32. a) Lone Pair on P b) Lone Pair on center O

36. Polar = (b), (c), (e)38.Ortho and meta44. Not enough p suborbitals46. SF2 = sp3, SF4 = sp3d

48. a) sp3 b) sp c) sp2 d) sp3d

e) sp3d2

52. b) N2H4 (sp3), N2 (sp) c) N2 stronger bond

54. a) sp3 (C-H), sp2 (C-O)b) 36 ve c) 26 ve-d) 2 ve- in double e) 8 ve- in lone pairs

56. a) 1, 120o 2, 120o 3, 105o

b) sp2, sp2, sp3

c) 21 bonds

62.

100. In2S (I) [Kr]5s24d10

InS (II) [Kr]5s14d10

In2S3 (III) [Kr]4d10

In(III) is smallest (least mutual electron repul)

In(III) has the highest lattice energy

102.a) C2H3Cl3O2 b) C2H3Cl3O2

c) Structure CCl3CH(OH)2