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Chapter 8Covalent Bonding

8.1 Molecular Compounds8.2 The Nature of Covalent Bonding

8.3 Bonding Theories

8.4 Polar Bonds and Molecules

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Molecular Shape

What information does a structural formula give you?

Structural formula

It tells us… 1) Which atoms are

bonded to which

2) Whether single, double or triple bonds are used.

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Molecular Shape

A structural formula is two-dimensional, so it does not give us a true representation of the arrangement of atoms. Molecules are 3-D!

Structural formula

3-D Model

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Molecular Shape

Why is the shape of a molecule VERY important?

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The shape of a molecule helps us predict some of its properties.

If water wasn’t “bent” it would have totally different properties.

Molecular Shape

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VSEPR Theory

• What is it? The theory scientist use to predict the shape of molecules.

VSEPR Theory

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VSEPR Theory(What we use to predict the shapes of molecules)

• First concept: Electron Domain

• Page 38-39, Questions 1-10.

VSEPR Theory

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VSEPR Theory: Checkpoint 1

How many electron domains?

VSEPR Theory

4 electron domains

(2 bonding, 2 nonbonding)

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VSEPR Theory: Checkpoint 1

How many electron domains?

VSEPR Theory

3 electron domains

(2 bonding, 1 nonbonding)

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VSEPR Theory: Checkpoint 1

How many electron domains?

VSEPR Theory

2 electron domains

(2 bonding, 0 nonbonding)

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VSEPR Theory: Checkpoint 1

How many electron domains?

VSEPR Theory

6 electron domains

(6 bonding, 0 nonbonding)

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VSEPR Theory: Checkpoint 1

True or False? All covalent bonds (single, double or triple) count as 1 electron domain.

TRUE

VSEPR Theory

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VSEPR Theory: Checkpoint 1

True or False? A non-bonding pair of electrons counts as 1 electron domain.

TRUE

VSEPR Theory

Also called a “lone pair”

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VSEPR Theory: Checkpoint 1

Electron domains (attract/repel) each other.

Repel

VSEPR Theory

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VSEPR Theory (what we use to predict 3-D shapes of molecules)

Valence-Shell Electron-Pair Repulsion theory

• All electron domains around an atom will be positioned as far apart as possible in three-dimensional space.

VSEPR Theory

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VSEPR Theory

• Second concept: Repulsions lead to 3-D Shapes

• Page 39-40, Questions 11-17.

VSEPR Theory

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VSEPR Theory: Checkpoint 2

Why is it possible to get larger angles separating electron domains in three-dimensions versus two-dimensions?

There is more space in three-dimensions than in two-dimensions.

VSEPR Theory

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VSEPR Theory: Checkpoint 2

True or False?Lone pairs and bonding pairs repel each other equally.

False. Lone pairs repelmore strongly.

VSEPR Theory

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VSEPR Theory: Checkpoint 2

Which would repel each other the most?a)Two bonded pairs.b)A bonded pair and a lone pair.c)Two lone pairs.

Two lone pairs.

VSEPR Theory

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Due Today: Finish the worksheet (#1-20)

Homework #1 VSEPR Homework on Page 42

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VSEPR Theory

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VSEPR Theory

2 electron domains 3 electron

domains4 electron domains

LinearTrigonal planar

Tetrahedral

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Trigonal planar

120o

VSEPR Theory

Bent

< 120o

3 electron domains

The name of the shape is determined by looking at the ATOMS only.

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Tetrahedral

109.5o

VSEPR Theory

4 electron domains

A tetrahedron is a 3-D shape with 4 sides

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Trigonal pyramid

107o

VSEPR Theory

4 electron domains

The name of the shape is determined by looking at the ATOMS only.

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Bent

104.5o

VSEPR Theory

4 electron domains

The name of the shape is determined by looking at the ATOMS only.

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Trigonal bipyramid

120o, 90o

VSEPR Theory

5 electron domains

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Seesaw

120o, 90o

VSEPR Theory

5 electron domains

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T-shaped

90o

VSEPR Theory

5 electron domains

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Octahedral

90o

VSEPR Theory

6 electron domains

An octahedron is a 3-D shape with 8 sides.

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Square pyramid

90o

VSEPR Theory

6 electron domains

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Square planar

90o

VSEPR Theory

6 electron domains

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What causes valence-electron pairs to stay as far apart as possible?

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What causes valence-electron pairs to stay as far apart as possible?

The repulsion between electron pairs due to their negative charges causes valence-electron pairs to stay as far apart as possible.

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Shared electrons and the valence electrons that are not shared affect the shape of a molecular compound, as the valence electrons stay as far apart from each other as possible.

BIG IDEA

Bonding and Interactions

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END OF 8.3

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