6.1 : Shapes of Molecules and Ions

Question 1

Why do molecules form different shapes?

Answer 1

The electron pairs repel one another so that they are arranged as far apart as possible.

This arrangement minimises repulsion and thus holds the bonded atoms in a certain shape.

Question 2

What is the shape and bond angle of a molecule with 4 bonded pairs of electrons? Is it symmetrical?

Answer 2

Tetrahedral
109.5

It is symmetrical

Question 3

What do the different lines represent in a 3D drawing?

Answer 3

Solid line = bond in the plane of the paper

Solid wedge = comes out of the plane of the paper

Dashed wedge = goes into the plane of the paper

Question 4

What is the difference in repulsion between bonded pair and lone pair electrons?

Answer 4

Lone pair = slightly closer to the central atom = occupies more space

Therefore it repels mor strongly that a bonded pair.

Question 5

What is the shape and bond angle of a molecule with 3 bonded pairs and 1 lone pair?

Answer 5

Pyramidal

107°

Question 6

What is the shape and bond angle of a molecule with 2 bonded pairs and 2 lone pairs?

Answer 6

non - linear

104.5°

Question 7

What is the shape and bond angle of a molecule with 2 bonded pairs of electrons?

Answer 7

Linear

180°

Question 8

What is the shape and bond angle of a molecule with 3 bonded pairs of electrons?

Answer 8

Trigonal planar

120°

Question 9

What is the shape and bond angle of a molecule with 6 bonded pairs of electrons?

Answer 9

Octahedral

90°