6.1 - Shapes of Molecules & Ions

Question 1

What is the electron pair repulsion theory?

Answer 1

• Since electrons have -ve charges, electron pairs repel each other
• Electron pairs determine the shapes of molecules, they repel each other as fr as possible to minimise repulsion
• Different numbers of electron pairs result in different shapes

Question 2

What do the 3 types of wedges represent?

Answer 2

A solid straight line represents a bond on the plane of the paper

A solid wedge shape represents a bond coming out of the plane of the paper

A dashed wedge shape represents a bond going into the plane of the paper

Question 3

What are the differences between bonded electron pairs and lone electron pairs?

Answer 3

• Lone pair electrons are closer to the central atoms, they occupy more space than a bonded pair
• Therefore lone pairs repel more than bonded pairs
• Per lone pair in an atom, the bond angle reduces by 2.5 degrees

Question 4

For a molecule with 2 bonded electron pairs/regions, give the name of the shape and its bond angle.

Answer 4

Shape: Linear
Angle: 180

Question 5

For a molecule with 3 bonded electron pairs/regions, give the name of the shape and its bond angle.

Answer 5

Shape: Trigonal planar
Angle: 120

Question 6

For a molecule with 4 bonded electron pairs/regions, give the name of the shape and its bond angle.

Answer 6

Shape: Tetrahedral
Angle: 109.5

Question 7

For a molecule with 3 bond pairs and 1 lone pair (4 electron regions), give the name of the shape and its bond angle.

Answer 7

Shape: Pyramidal
Angle: 107

Question 8

For a molecule with 2 bond pairs and 2 lone pair (4 electron regions), give the name of the shape and its bond angle.

Answer 8

Shape: Non-linear (bent)
Angle: 104.5

Question 9

Does the electron pair repulsion theory apply to ions as well?

Answer 9

Yes