Shapes of molecules

Question 1

How do we predict the shape of a molecule

Answer 1

By using electron pair repulsion theory

Question 2

Describe what is meant by electron pair repulsion theory

Answer 2

• Each pair of electrons around the atom repels all the other pairs
• Pairs of electrons take up positions, far away from each other as possible, in order to minimise repulsion

Question 3

The type of molecule that has an 180 degree bond angle, and 2 pairs of electrons is called

Answer 3

A linear molecule

Question 4

The type of molecule that has an 120 degree bond angle, and 3 pairs of electrons, is called

Answer 4

A trigonal planar molecule

Question 5

The type of molecule that has an 109 degree bond angle, and 4 pairs of electron is called

Answer 5

• A tetrahedral molecule

Question 6

The type of molecule that has an 120 degree bond angle and 5 pairs of electrons is called

Answer 6

A trigonal pyramid

Question 7

The type of molecules that has a 90 degree bond angle and 8 pairs of electrons is called

Answer 7

An octahedral molecule

Question 8

Name 3 examples where lone pairs affects shape

Answer 8

• Ammonia
• Water
• Chlorine tetraflouride ion

Question 9

Do lone pairs or bonding pairs of electrons have a greater repulsion

Answer 9

Lone pairs

Question 10

Describe how to get from a tetrahedral molecule to a pyramidal molecule

Answer 10

Replace one bonding pair with a lone pair

Question 11

Describe how to get from a tetrahedral molecule to a v-shaped molecule

Answer 11

Replace another bonding pair with a lone pair

Question 12

What are v-shaped molecules also known as

Answer 12

Non-linear