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Objectives. Objectives OK State summary page Objectives To understand the VSEPR theory model To learn to predict electronic geometries from the number.

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Presentation on theme: "Objectives. Objectives OK State summary page Objectives To understand the VSEPR theory model To learn to predict electronic geometries from the number."— Presentation transcript:

1

2 Objectives

3 OK State summary page Objectives To understand the VSEPR theory model
To learn to predict electronic geometries from the number of regions of high e- density Download VSEPR Charts Here To understand electronic structure and bond angles OK State summary page

4 A. The VSEPR Model Valence shell electron pair repulsion (VSEPR) model Each pair of e-s in a valence shell are significant. e- pairs about the central atom repel each other. They arrange to minimize repulsion forces. Electronic geometry is determined by the number of e- pairs (RHED) about a central atom. Region of high e- density – (RHED) any e- pair or bond I, II, or III Central atom – any atom bonded to > 1 other atom Bonded atom – any atom bonded to a central atom

5 A. Molecular Structure Linear structure – atoms in a line Carbon dioxide CO2 OCTET?

6 A. Molecular Structure Trigonal planar – atoms in a triangle Boron trifluoride BF3 OCTET?

7 A. Molecular Structure Tetrahedral structure methane CH4 OCTET?

8 A. Molecular Structure Trigonal bipyramidal PF5 OCTET? 120o equatorial – 90o axial trigonal bipyramidal

9 A. Molecular Structure Octahedral SF6 OK State Website OCTET? All 90o

10 Rules for using the VSEPR model to predict the e- geometry:
B. The VSEPR Model Rules for using the VSEPR model to predict the e- geometry: Draw the Lewis-Dot Bonded atoms follow octet Central atom doesn’t have to (exceptions) Any extra e-s get paired around central atom 2. Count the regions of high e-density (RHED) (e- pair OR bond I, II, III) about the Central Atom 3. Refer to Table to determine e- geometry

11 B. The VSEPR Model BeCl2 Two Bonds (2 RHED) linear

12 B. The VSEPR Model BF3 Three Bonds (3 RHED) trigonal planar

13 B. The VSEPR Model CCl4 Four Bonds (4 RHEDS) tetrahedral

14 B. The VSEPR Model PF5 Five Bonds (5 RHEDS) Trigonal bipyramidal

15 B. The VSEPR Model SF6 6 Bonds (6 RHEDS) All 90o –octahedral

16 B. The 5 types of electronic geometries

17 B. The VSEPR Model Practice
Draw the Lewis Dot Structure and predict the Electronic Geometry of the following: BeCl2 CH3F SF6 BF3 PCl5 Electronic geometries are 1 of 5 options

18 B. The VSEPR Model Practice
Electronic Geometry: BeCl2 Linear CH3F Tetrahedral SF6 Octahedral BF3 Trigonal Planar PCl5 Trigonal Bipyramidal Electronic geometries are 1 of 5 options

19 H2O NO2- SO3-2 XeF2 ClF3 BrF5 IF4-
A. Molecular Structure Draw the Lewis Dot and Predict the Electronic Geometry of the following: H2O NO2- SO3-2 XeF2 ClF3 BrF5 IF4-

20 XeF2 Trigonal Bipyramidal ClF3 Trigonal Bipyramidal BrF5 Octahedral
A. Molecular Structure Electronic Geometry: H2O Tetrahedral NO2- Trigonal Planar SO3-2 Tetrahedral XeF2 Trigonal Bipyramidal ClF3 Trigonal Bipyramidal BrF5 Octahedral IF4- Octahedral

21 To understand the VSEPR theory model
Objectives Review To understand the VSEPR theory model To learn to predict electronic geometries from the number of regions of high e- density To understand electronic structure and bond angles Work Session: Review Page 433 # 1, 4, 5 (e- geometry)

22 To predict the polarity of a molecule
Objectives To learn to predict MOLECULAR geometries from the number of paired and unpaired e-s To predict the polarity of a molecule To understand the effect of an unshared pair on bond angles OK State summary page

23 A. Molecular Structure The molecular geometry is a three dimensional arrangement of the atoms in a molecule. What do they actually look like? Water - bent

24 How do we predict the Molecular Geometry?
A. Molecular Structure How do we predict the Molecular Geometry? Same as Electronic Geometry, only more options… 1. Draw the Lewis Dot 2. Count the RHEDS 3. Determine the General Formula (ABxUy) 4. Refer to Table

25 A. Molecular Structure AB2U Trig Planar Bent

26 A. Molecular Structure AB3U Tetrahedral Trigonal Pyramidal

27 A. Molecular Structure AB2U2 Tetrahedral Bent

28 A. Molecular Structure AB4U Trigonal Bipyramidal Seesaw

29 A. Molecular Structure AB3U2 Trigonal Bipyramidal T - shaped

30 A. Molecular Structure AB2U3 Trigonal Bipyramidal Linear

31 A. Molecular Structure AB5U Octahedral Square Pyramidal

32 A. Molecular Structure AB4U2 Octahedral Square Planar

33 A. Molecular Geometries
Seesaw

34 H2O Find the General Formula ABxUy I3- O3 ICl3 NH3 IF5 XeF4 SF4
A. Molecular Structure Draw the Lewis Dot and Predict the ELECTRONIC and MOLECULAR Geometry of the following: H2O Find the General Formula ABxUy I3- O3 ICl3 NH3 IF5 XeF4 SF4

35 I3- Trig Bipyramidal Linear O3 Trig Planar Angular
A. Molecular Structure ELECTRONIC and MOLECULAR Geometry H2O Tetrahedral Angular I Trig Bipyramidal Linear O3 Trig Planar Angular ICl3 Trig Bipyramidal T-shaped NH3 Tetrahedral Trig Pyramid IF5 Octa Squ Pyramid XeF4 Octa Squ Planar SF4 Trig Bipyramidal See-Saw

36 Molecular Structures If y=0 in ABxUy, then molecular geom = e- geom
Bent Trigonal Planar

37 BeF2 SO2 BBr3 NH3 CHCl3 BrF5 XeF2
A. Molecular Structure Draw the Lewis Dot and predict both the ELECTRONIC and MOLECULAR Geometry of the following: Show Dipole Moment (3options) BeF2 SO2 BBr3 NH3 CHCl3 BrF5 XeF2

38 SF4 ClF3 XeF4 CH2ClBr SbCl5 SeF6 BI3
A. Molecular Structure Draw the Lewis Dot and predict both the ELECTRONIC and MOLECULAR Geometry of the following: Show the dipole if needed. SF4 ClF3 XeF4 CH2ClBr SbCl5 SeF6 BI3

39 B. Molecular Structure - Polarity
Consider HF and electronegativities:

40 B. Molecular Structure - Polarity
We can use the same analysis on a molecular level to determine if it is polar:

41 B. Molecular Structure - Polarity
Draw the Lewis Dot, analyze each bond, and predict the overall polarity of the molecule: BeBr2 XeBr2 BeFI CH3Cl SbCl5 SeF5Br BFI2

42 B. Molecular Structure - Polarity
Draw or look over the Lewis Dot and predict the overall polarity of the molecule: SF4 ClF3 XeF4 CH3Br SbCl5 NH3 BrI5

43 B. Molecular Structure -
The effect of lone e- pairs on bond angles: Lone pairs of e- repel each other MORE than bonding pairs of e-s thereby REDUCING the bond angles: LP/LP >> LP/BP > BP/BP CH4 NH3 H2O

44 OK State summary page Objectives Review
To learn to predict MOLECULAR geometries from the number of paired and unpaired e-s To predict the polarity of a molecule To understand the effect of an unshared pair on bond angles Work Session: Review Page 433 # 2, 3, #5 Predict the molecular geometry AND tell if the molecule is polar Give an example of one non-polar molecule. OK State summary page

45 To understand the Valence Bond (VB) Theory
Objectives To understand the Valence Bond (VB) Theory To describe HOW the exceptions to the octet rule occur To use the VB theory to predict the orbital hybridization about a central atom

46 B. The VB Theory Let’s consider the orbital diagram for Be Be ______ ______ ______ ______ ______ 1s s p Now, let’s consider BeCl2: Cl—Be—Cl How can it bond if the valence 2s orbital is full? Hybridization of the 2s and one of the 2p suborbitals to form two sp orbitals Be ______ ______ ______ ______ Be ______ 1s sp sp sp 1s sp

47 B. The VB Theory Let’s visualize the hybrid orbitals: s p sp

48 B. The VB Theory Let’s visualize the hybrid orbitals: Be 1s2s sp sp

49 B. The VB Theory The sp hybridization of Be Be 3p of Cl sp sp p of Cl ______ ______ ______ ______ Be ______ ______ ______ ______ 3p of Cl sp sp p of Cl

50 B. The VB Theory Hybridization of other orbitals occurs in a similar fashion: sp2 (3 RHEDS)

51 B. The VB Theory sp3 (4 RHEDS)

52 B. The VB Theory

53 B. The VB Theory sp3d (5 RHEDS)

54 B. The VB Theory Hybridization Summary
Valence Electron Pair Geometry Number of Orbitals Hybrid Orbitals Linear 2 sp Trigonal Planar 3 sp2 Tetrahedral 4 sp3 Trigonal Bipyramidal 5 sp3d Octahedral 6 sp3d2

55 C. The VB Theory Hybridization
Draw or look over the Lewis Dot and Predict the VB Hybridization of the following: H2O I3- O3 ICl3 NH3 IF5 XeF4 SF4

56 C. The VB Theory Hybridization
Draw or look over the Lewis Dot and Predict the VB Hybridization of the following: BeF2 SO2 BBr3 NH3 CHCl3 BrF5 XeF2

57 C. The VB Theory Hybridization
How about Double and triple bonds? C2H σ & 1 π bond C2H σ & 2 π bonds

58 C. The VB Theory Hybridization
C2H σ & 2 π bonds

59 Objectives Review To understand the Valence Bond (VB) Theory To describe HOW the exceptions to the octet rule occur To use the VB theory to predict the orbital hybridization about a central atom Work Session: Draw the Lewis Dot and predict the hybridization about the central atom: AlCl3, NCl3, SiH4, SF6, MgCl2, IF4-, AlH4-, NH4+, PCI3, CIO3-

60 B. The VSEPR Model

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