6.1 - Shapes of molecules and ions

Question 1

What is the electron-pair theory used for?

Answer 1

It is used in chemistry for explaining and predicting the shapes of molecules and polyatomic ions

Question 2

What is the electron-pair theory?

Answer 2

• The electron pairs surrounding a central atom determine the shape of the molecule or ion
• The electron pairs repel one another so that they are arranged as far apart as possible
• The arrangement of electron pairs minimised repulsion and thus holds the bonded atoms in a definite shape
• Different numbers of electron pairs result in different shapes

Question 3

What does a solid line represent?

Answer 3

A bond in the plane of the paper

Question 4

What does a solid wedge represent?

Answer 4

A bond that comes out of the plane of the paper

Question 5

What does a dotted wedge represent?

Answer 5

A bond that goes into the plane of the paper

Question 6

Describe the shape and bond angle of a tetrahedral shape

Answer 6

• 4 Bonded pairs
• 0 Lone pairs
• 109.5°

Question 7

Describe the shape and bond angle of a pyramidal shape

Answer 7

• 3 Bonded pairs
• 1 Lone pair
• 107°

Question 8

Describe the shape and bond angle of non-linear shape

Answer 8

• 2 Bonded pairs
• 2 Lone pairs
• 104.5°

Question 9

Describe the shape and bond angle of linear shape

Answer 9

• 2 bonding regions
• 180°

Question 10

Describe the shape and bond angle of trigonal planar shape

Answer 10

• 3 bonding regions
• 120°

Question 11

Describe the shape and bond angle of octahedral shape

Answer 11

• 6 bonding regions
• 90°