+

Bonding Part III

Unit 5: BondingMrs. Callender

V SE P

R

+Lesson Essential Question:

How do I Predict Molecular Shape?

+VSEPR stands for….ValenceShellElectronPairRepulsion

The structure around a given atom is determined principally by minimizing electron pair repulsions.

+ How to predict a VSEPR Structure?

1. Draw a Lewis Dot Structure

2. Put pairs as far apart as possible.

3. Determine position of atoms from the way the electron pairs are shared and unshared.

4. Determine the name of the molecular structure from positions of the atoms and electron pairs.

+ Electron Pair Count and Geometry

A number of possibilities – seven pairs on the central atom.

Linear – two pairs on the central atom.

Trigonal – three pairs on the central atom.

Trigonal Bipyramidal – five pairs on the central

atom.

Tetrahedral – four pairs on the central atom.

Octahedral – six pairs on the central atom.

+ How do I figure out the geometry?

Electron Pair #

GeometricalArrangement

Types of e- Pairs

Molecular Shapes Ex’s Ball and Stick

Model

2 Linear,180o

2 BP Linear

BeCl2

Be– 2 valence e-2 Cl – 14 valence e-Total = 16 valence e- C

lBe

Cl

Two Bonding Pair (BP) of electrons and no unbonded pair of electrons fits the Linear criteria.

AX2E0

+Electron Pair #

GeometricalArrangement

Types of e- Pairs

Molecular Shapes Ex’s Ball and Stick

Model

3 Trigonal Planar,120o

3 BP Trigonal Planar

BF3

B– 3 valence e-3 F – 21 valence e-Total = 24 valence e- F B F

FThree Bonding Pair (BP) of electrons and no unbonded pair of electrons fits the Trigonal Planar criteria.AX3E0

+Electron Pair #

GeometricalArrangement

Types of e- Pairs

Molecular Shapes Ex’s Ball and Stick

Model

3 Trigonal Planar,120o

2 BP1 LP

BentSO2

S – 6 valence e-2 O– 12 valence e-Total = 18 valence e- O S O

This structure has resonance so the bonds between the S and O represent 2 Bonding Pairs (BP) of electrons.

One Lone Pair (LP) of electrons.

AX2E1

+Electron Pair #

GeometricalArrangement

Types of e- Pairs

Molecular Shapes Ex’s Ball and Stick

Model

4 Tetrahedral109.5o 4 BP

Tetrahedral CH4

C – 4 valence e-4 H– 4 valence e-Total = 8 valence e-

H CH

HH

4 Bonding Pairs of electrons and no Lone Pair of electrons has this compound as a Tetrahedral.

AX4E0

+Electron Pair #

GeometricalArrangement

Types of e- Pairs

Molecular Shapes Ex’s Ball and Stick

Model

4 Tetrahedral109.5o 3 BP

1 LP

Trigonal Pyramidal NH3

N – 5 valence e-3 H– 3 valence e-Total = 8 valence e-

H N HH

3 Bonding Pairs of electrons and one Lone Pair of electrons has this compound as a Trigonal Pyramidal.

AX3E1

+Electron Pair #

GeometricalArrangement

Types of e- Pairs

Molecular Shapes Ex’s Ball and Stick

Model

4 Tetrahedral109.5o 2 BP

2 LP

BentH2O

2 H – 2 valence e-O– 6 valence e-Total = 8 valence e- H O H

3 Bonding Pairs of electrons and Two Lone Pair of electrons has this compound as a Trigonal Pyramidal.AX2E2

+Electron Pair #

GeometricalArrangement

Types of e- Pairs

Molecular Shapes Ex’s Ball and Stick

Model

5 Trigonal Bipyramida

l120o, 90o

5 BPTrigonal

BipyramidalPCl5

P – 5 valence e- 5 Cl – 35 valence e-Total = 40 valence e-

Cl

PCl

Cl C

lCl

v

5 Bonding Pairs of electrons and no Lone Pair of electrons has this compound as a Trigonal Bipyramidal

Some elements can have EXPANDED Octets which means they can have more than the eight electrons around the central atom.

AX5E0

+Electron Pair #

GeometricalArrangement

Types of e- Pairs

Molecular Shapes Ex’s Ball and Stick

Model

5 Trigonal Bipyramida

l120o, 90o

4 BP1 LP

See-SawSF4

S – 6 valence e-4 F – 28 valence e-Total = 34 valence e-

F SF

FF

v

4 Bonding Pairs of electrons and One Lone Pair of electrons has this compound as a See Saw

Some elements can have EXPANDED Octets which means they can have more than the eight electrons around the central atom.

AX4E1

+Electron Pair #

GeometricalArrangement

Types of e- Pairs

Molecular Shapes Ex’s Ball and Stick

Model

5 Trigonal Bipyramida

l120o, 90o

3 BP2 LP

T-ShapedICl3

I – 7 valence e-3 Cl – 21 valence e-Total = 28 valence e-

Cl

ICl

Cl

3 Bonding Pairs of electrons and Two Lone Pair of electrons has this compound as T-Shaped.

Some elements can have EXPANDED Octets which means they can have more than the eight electrons around the central atom.

AX3E2

+Electron Pair #

GeometricalArrangement

Types of e- Pairs

Molecular Shapes Ex’s Ball and Stick

Model

5 Trigonal Bipyramida

l120o, 90o

2 BP3 LP

LinearI3-1

3 I – 21 valence e--1 charge – 1 valence e-Total = 22 valence e-

I I I 2 Bonding Pairs of electrons and Three Lone Pair of electrons has this compound as Linear.

Some elements can have EXPANDED Octets which means they can have more than the eight electrons around the central atom.

AX2E3

+Electron Pair #

GeometricalArrangement

Types of e- Pairs

Molecular Shapes Ex’s Ball and Stick

Model

6 Octahedral90o 6 BP

Octahedral SF6

S – 6 valence e-6 F – 42 valence e-Total = 48 valence e-

Some elements can have EXPANDED Octets which means they can have more than the eight electrons around the central atom.

F S F F F

F F 6 Bonding Pairs of electrons and no Lone Pair of electrons has this compound as an Octahedral.AX6E0

+Electron Pair #

GeometricalArrangement

Types of e- Pairs

Molecular Shapes Ex’s Ball and Stick

Model

6 Octahedral90o 5 BP

1 LP

Square Pyramid

IF5

I – 7 valence e-5 F – 35 valence e-Total = 42 valence e-

Some elements can have EXPANDED Octets which means they can have more than the eight electrons around the central atom.

F I F F F

F 5 Bonding Pairs of electrons and One Lone Pair of electrons has this compound as a Square Pyramidal.AX5E1

+Electron Pair #

GeometricalArrangement

Types of e- Pairs

Molecular Shapes Ex’s Ball and Stick

Model

6 Octahedral90o 4 BP

2 LP

Square Planar

XeF4

Xe – 8 valence e-4 F – 28 valence e-Total = 32 valence e-

Some elements can have EXPANDED Octets which means they can have more than the eight electrons around the central atom.

FXe

F F F

4 Bonding Pairs of electrons and Two Lone Pair of electrons has this compound as a Square PlanarAX4E2

+Electron Pair #

GeometricalArrangement

Types of e- Pairs

Molecular Shapes Ex’s Ball and Stick

Model

7 Pentagonal Bipyramid 7 BP

Pentagonal Bipyramid

IF7

I – 7 valence e-7 F – 49 valence e-Total = 56 valence e-

Some elements can have EXPANDED Octets which means they can have more than the eight electrons around the central atom.

AX7E0

FIF

F F

F F F

7 Bonding Pairs of electrons and No Lone Pair electrons has this compound as a Pentagonal Bipyramid.

+Electron Pair #

GeometricalArrangement

Types of e- Pairs

Molecular Shapes Ex’s Ball and Stick

Model

7 Pentagonal Bipyramid 6 BP

1 LP

Pentagonal Pyramidal

IOF5-2

I – 7 valence e-5 F – 35 valence e-O – 6 valence e--2 charge – 2 valence e-Total = 50 valence e-Some elements

can have EXPANDED Octets which means they can have more than the eight electrons around the central atom.

AX6E1

IO

F F

F F F

6 Bonding Pairs of electrons and One Lone Pair electrons has this compound as a Pentagonal Pyramidal.

+Dotted Line and Wedge Model

Linear AX2E0

Trigonal Planar AX3E0

Bent AX2E1

+Dotted Line and Wedge Model

Tetrahedral AX4E0

Trigonal Pyramidal AX3E1

Bent AX2E2

+Dotted Line and Wedge Model

Octahedral AX6E0

Square Pyramid AX5E1

Square Planar AX4E2

+Dotted Line and Wedge Model

Pentagonal Bipyramid AX7E0

Pentagonal Pyramid AX6E1