CHEMICAL BONDING

VSEPR Theory

Objectives

◻ Predict the shape of a molecule based on the VSEPR theory.

Warm-Up: Draw Lewis Structures for the following:

IONIC COVALENT

MgI2 CF4

HOMEWORK CHECK

VSEPR

Stands for:

⬜ V-Valence

⬜ S-Shell

⬜ E-Electron

⬜ P-Pair

⬜ R-Repulsion

Basically Electrons don’t like each other very much!

A Few Important Terms:

Central Atom:

Lone Pairs: centralatom

Bonds:

VSEPR: Valence Shell ElectronPair Repulsion

Atoms Attached to the

Central Atom

Lone Pairs on

Central Atom

Shape

4 0 Tetrahedral

3 1 Trigonal Pyramidal

3 0 Trigonal Planar

2 1 or 2 Bent

2

OR a 2 atom molecule

0

H2, N2, HCl for example

Linear

IONIC COMPOUND --------- Lattice (Salt)

Lone pairs = unshared electrons

What About Ionic Structures????

◻ Lattice- Ionic Compounds form a 3D lattice structure when the cations and anions come together via electrostatic attraction.

◻ The Lattice has a repeating structure - NaCl

MOLECULAR GEOMETRY EXPLORATION

CH4Step 1: Draw Lewis Structure

Step 2: Examine Central Atom

Step 3: Count # of atoms bonded around central atom

Step 4: Count # of lone pairs around central atom

Step 5: Determine the Geometry

Example

◻ Draw the Lewis Structure. Predict the shape.

◻ H2O

Example

◻ Draw the Lewis Structure. Predict the shape.

◻ H2O

Atoms bonded = 2

Lone pairs = 2

BENT

Example

◻ Draw the Lewis Structure. Predict the shape.

◻ NH3

Example

◻ Draw the Lewis Structure. Predict the shape.

◻ NH3

Atoms Bonded = 3

Lone Pairs = 1

TRIGONAL PYRAMIDAL

Example

◻ Draw the Lewis Structure. Predict the shape.

◻ CH4

Example

◻ Draw the Lewis Structure. Predict the shape.

◻ CH4

Atoms bonded = 4

Lone pairs = 0

TETRAHEDRAL

Example

◻ Draw the Lewis Structure. Predict the shape.

◻ SO3

Example

◻ Draw the Lewis Structure. Predict the shape.

◻ SO3***** Sulfur is the CENTRAL ATOM

Trigonal Planar

3 atoms bonded to Sulfur

0 lone pairs on Sulfur

You Try

Draw the Lewis Structure &

Predict the Shape of the Following:

◻ AsH3

◻ SiF4

◻ CO2

You Try

Draw the Lewis Structure &

Predict the Shape of the Following:

◻ PF3

◻ SiF4

◻ CO2

Molecule or Ion_______________

# valence

electrons

Lewis Dot

Structure

# Lone

Pairs

# of atoms

Bonded to

central atom

VSEPR

Shape

Are there Ionic

Bonds in the

structure?

Is the molecule or

ion polar? Why?

CH44 + 1 + 1 + 1 + 1=8

0 4 Tetrahedral Yes No. No lone pairs.

All atoms bonded

are identical

CH2F2

NH3Trigonal Pyramidal Yes Yes. There is a

lone pair on the

central atom

AsI33

HCNLinear

N2- - - - - - - - - - - - - - No No. Atoms are

Identical

H2OBent

SCl22

SO3Trigonal Planar

CF2O3

Molecule or Ion_______________

# valence

electrons

Lewis Dot

Structure

# Lone

Pairs

# of atoms

Bonded to

central atom

VSEPR

Shape

Are there Ionic

Bonds in the

structure?

Is the molecule or

ion polar? Why?

HBr- - - - - - - - - - - - - -

SiCl4

CH2O

NO2-1

CO3-2

OH-1- - - - - - - - - - - - - -

SO4-2

CO2

NO3-1

NH4+

Six Shapes Practice

A B C

DE

F

Six Shapes

A B C

DE

F

TRIGONAL PLANARTETRAHEDRAL TRIGONAL PYRAMIDAL

LINEAR

IONIC – LATTICE/SALT

BENT

Try This !!

Exit Ticket

(1) Draw the Lewis Structure for Carbon Dioxide (CO2)

(2) Predict the geometric shape of carbon dioxide

(3) How many lone pairs of electrons are on the central

atom?

(4) Describe the bond(s) between the carbon atom and

the two oxygen atoms.

(5) How many atoms of each type are in 8 Pb(NO3)2 ?

HOMEWORK:

Finish Molecular Geometry Exploration

Quiz: Tuesday 10/8/18

Lewis Structures & VSEPR

Unit 4 TEST Friday 10/12/18