G10_4.4: Molecular Shapes

Molecular Shapes

Lesson 4

Focus Question

What shapes do molecules form?

New Vocabulary

VSEPR model

hybridization

Review Vocabulary

atomic orbital: the region around an atom’s nucleus
that defines an electron’s probable location

Multiple Choice

Region of high probability of finding an electron

• atomic orbital

• ground state

• Heisenberg uncertainty principle

• electron configuration

Multiple Choice

s orbitals are _____shaped

• spherical

• dumbbell

• circular

Multiple Choice

p - orbitals are ______shaped

• spherical

• dumb-belled

• circular

Multiple Choice

VSEPR stands for ________ theory.

• Valence Structure of Electron Pyramids and Regression

• Varied Structures of Electrons Paired and Replaced

• Varied Shell Energy of Protons and Radiation

• Valence Shell Electron Pair Repulsion

VSEPR Model

• The molecular geometry

(shape) of a molecule can be
determined using the Valence
Shell Electron Pair Repulsion
model, or VSEPR model.

• It is based on an arrangement

that minimizes the repulsion of
shared and unshared electron
pairs around the central atom.

VSEPR Model

Bond Angle
• Electron pairs repel each other and cause

molecules to be in fixed positions relative to
each other.

• Unshared electron pairs called LONE PAIRS also determine the shape of a molecule.

• Electron pairs are located in a molecule as far

apart as they can be.

Multiple Choice

 A lone pair is defined as

• A pair of bonding electrons

• One non-bonding electron

• A pair of non-bonding electrons

• A pair of electrons on the central atom

Multiple Choice

The ------ model helps predict the shape of a molecule.

• VESPR

• Electron

• Lewis

Multiple Choice

The model is based on the principle that electron pairs around the central atom ------ each other.

• bond

• attract

• repel

Multiple Choice

The ------ of the molecule determines the properties of the compounds.

• density

• shape

• mass

Hybridization

• Hybridization occurs when two things are combined

and the result has characteristics of both.

• If electrons come from two different atomic orbitals,

such as a p or an s, they must rearrange or combine
into a hybrid orbital with the same shape and energy
level.

Multiple Choice

Which statement is TRUE, based on the diagram provided?

• atomic orbital overlap to produce sigma bond

• s orbital overlap to produce π bond

• s orbital overlap with s orbital to produce sigma bond

• p orbital overlap to produce π bond

Multiple Choice

Diagram below shows

• formation of hybrid orbital

• atomic orbital overlap to produce hybrid orbital

• atomic orbital overlap to form sp hybrid orbital

• s orbital overlap with p orbital to form sp hybrid orbital

Multiple Choice

Which of the statement is TRUE?

• s orbital overlap with p orbitals to form sp hybrid orbital

• s orbital with two p orbitals to form one sp² hybrid orbital

• s orbital with two p orbitals to form two sp² hybrid orbital

• s orbital with two p orbitals to form three sp² hybrid orbital

Multiple Choice

What is the VSEPR theory used to predict?

• Bond Strength

• Polarity

• Molecular Shape

• Electronegativity

Multiple Choice

The covalent bond forms between

• a metal and nonmetal

• a nonmetal and nonmetal

• a metal and metal

Hybridization

• Consider the bonding involved in the methane

molecule (CH4) on the image below.

• The hybrid orbitals in a carbon atom are

shown in blue.

Hybridization

• Carbon initially has only 2

electrons in its p orbital.

• A 1 s electron is promoted

from the s to the p orbital
so a total of 4 unpaired
electrons can be shared.

• These electrons undergo

hybridization, which forms
four hybrid sp3 orbitals that
can bond with 4 hydrogen
atoms.

Multiple Choice

Which molecule will undergo sp³ hybridization?

• CO₂

• NH₃

• SO₃

• NO₂

Multiple Choice

Molecule CO₂

• undergoes sp² hybridisation

• has 2 σ bond and 2 π bond

• undergoes sp³d hybridisation

• is trigonal planar molecule

Hybridization

• The number of atomic orbitals that mix and form the

hybrid orbital equals the total number of electron pairs.

• The number of hybrid orbitals formed equals the

number of atomic orbitals mixed (sigma bonds).

Hybridization

• For example, the table on the next slide shows that AlCl3

has a total of three pairs of electrons and VSEPR predicts
a trigonal planar shape.

• The shape results when one s and two p orbitals on the

central atom, Al, mix and form three identical sp2 hybrid
orbitals.

Multiple Choice

What is the the shape of this molecule according to VSEPR theory?

• Linear

• Tetrahedral

• Trigonal Planar

• Trigonal pyramidal

Multiple Choice

What is the hybridization of a linear molecule?

• sp

• sp²

• sp³

• sp³d

Multiple Choice

What is the hybridization of this molecule shown above

• sp

• sp²

• sp³

• sp⁴

Multiple Choice

Which of the following images represents a Trigonal Planar molecular geometry?

Hybridization

• BeCl2 has two pairs of electrons shared with the

central Be atom. The bonding electrons have
maximum separation and a bond angle of 180. The
shape is linear.

Molecule

Total
Pairs

Shared
Pairs

Lone
Pairs

Hybrid
Orbitals

Molecular Shape

BeCl2
2

2

0

sp

AlCl3
3

3

0

sp2

Multiple Choice

Diagram showing Beryllium atom undergoing hybridization forming

• two sp hybrid orbitals

• sp hybrid orbitals

• one sp hybrid orbitals

• sp² hybrid orbitals

Multiple Choice

Diagram show Beryllium atom undergoing hybridization to form

• BeCI

• BeCI₂

• BeCI₃

• BeCI₄

Hybridization

• Lone pairs also occupy hybrid orbitals.
• Single, double, and triple bonds occupy only one hybrid orbital.

Thus, CO2, with two double bonds, forms sp hybrid orbitals.

Hybridization

• The H2O molecule has sp3 orbitals. There are two

lone pairs on the central oxygen atom in H2O.
Therefore, there must be four hybrid orbitals—two
for bonding and two for lone pairs. The bent shape
is shown on the next slide.

Multiple Choice

In a water (H₂O) molecule, the polar bonds between the oxygen atom and the hydrogen atoms do not cancel out because the molecule is bent.

• True

• False

Hybridization

Molecule

Total
Pairs

Shared
Pairs

Lone
Pairs

Hybrid
Orbitals

Molecular Shape

CH4
4

4

0

sp3

NH3
4

3

1

sp3

H2O

4

2

2

sp3

Hybridization

Molecule

Total
Pairs

Shared
Pairs

Lone
Pairs

Hybrid
Orbitals

Molecular Shape

NbBr5
5

5

0

sp3d

SF6
6

6

0

sp3d2

Multiple Choice

What molecule could this be? 

• BF₃

• CH₄

• H₂O

• CO₂

Multiple Choice

Which of the following shapes has an unshared pairs of electrons on the central atom? 

• Bipyramidal

• Bent

• Trigonal Planar

• Tetrahedral

Multiple Choice

Which of the following is the correct Lewis structure for the compound PBr₃?

• structure A

• structure B

• structure C

• structure D

Multiple Choice

VSEPR theory is to

• determine the number of bonding and lone pairs electrons

• determine the number of ECC

• determine the shape and geometry of molecule

• determine the lewis structure of molecule

Multiple Choice

How many sigma and pi bonds does this have? 

• 3 sigma and 2 pi

• 5 sigma and 5 pi

• 5 sigma and 0 pi

• 0 sigma and 5 pi

Think of the Quiz answers before moving

to the next slide

Quiz

It is based on an arrangement that maximizes the
attraction of shared electrons and the repulsion of
shared electron pairs.

D

It is based on an arrangement that maximizes the
repulsion of shared and unshared electron pairs.

C

It is based on an arrangement that minimizes the
repulsion of shared and unshared electron pairs.

B

It stands for Valence Shell Electron Pair Repulsion.

A

Which of the following is not true of the VSEPR
model?

1.

Quiz

It is based on an arrangement that maximizes the
attraction of shared electrons and the repulsion of
shared electron pairs.

D

It is based on an arrangement that maximizes the
repulsion of shared and unshared electron pairs.

C

It is based on an arrangement that minimizes the
repulsion of shared and unshared electron pairs.

B

It stands for Valence Shell Electron Pair Repulsion.

A

Which of the following is not true of the VSEPR
model?

1.

CORRECT

Quiz

trigonal planar

D

trigonal pyramidal

C

bent

B

tetrahedral

A

A molecule has three single covalent bonds,
one lone pair, and sp3 hybrid orbitals. What is
its likely shape?

2.

Quiz

trigonal planar

D

trigonal pyramidal

C

bent

B

tetrahedral

A

A molecule has three single covalent bonds,
one lone pair, and sp3 hybrid orbitals. What is
its likely shape?

2.

CORRECT

Quiz

180°

D

120°

C

109.5°

B

A

What are the bond angles in a trigonal planar
molecule?

3.

90°

Quiz

180°

D

120°

C

109.5°

B

A

What are the bond angles in a trigonal planar
molecule?

3.

CORRECT

90°

Quiz

octahedral

D

trigonal bipyramidal

C

trigonal pyramidal

B

tetrahedral

A

A molecule has 6 shared pairs of electrons and no
lone pairs of electrons. Its hybrid orbitals are sp3d2.
What is its likely shape?

4.

Quiz

octahedral

D

trigonal bipyramidal

C

trigonal pyramidal

B

tetrahedral

A

A molecule has 6 shared pairs of electrons and no
lone pairs of electrons. Its hybrid orbitals are sp3d2.
What is its likely shape?

4.

CORRECT