Topic 2: Metalic Bonding And Shapes

Question 1

Describe the bonding in platinum

Answer 1

Metal cations in a sea of delocalised electrons
Metallic bonding is the electrostatic forces of attraction between cations and electrons

Question 2

Explain why the bond angle in water is less than the bond angle in ammonia

Answer 2

Oxygen has one more lone pair than nitrogen (O has 2 N has 1)
Lone pair - lone pair repulsion is greater so reduces bond angle

Question 3

Predict the bond angle in chloric (1) acid and explain answer

Answer 3

104.5

2 bond pairs and 2 lone pairs of electrons in a valence shell of oxygen atoms
Valence electron pairs at minimum repulsion
Lone pair repulsion is greater than bond pair repulsion
Tetrahedral bond angle is reduced

Question 4

Ammonia and boron triflouride react to form a compound NH3BF3 which contains a dative covalent bond.
Each of the molecules, NH3 and BF3 has a different feature of its electronic structure that allows this to happen. Use these two different features to explain how a dative covalent bond is formed

Answer 4

Donation of a lone pair of electrons from the nitrogen atom to the boron atom which is electron deficient (only 6 es on outer shell)

Question 5

Using electron pair repulsion theory, explain the shape of the SnCl2 molecule

Answer 5

The shape is BENT as the 3 electron pairs on Sn repel one another

Question 6

Explain why a phosphorus (III) chloride molecule has a pyramidal shape and a bond angle less than 109.5

Answer 6

Pyramidal there are 4 pairs : 3 bonding pairs and 1 lone pair of electrons around the central P atom and these are arranged to minimise repulsion
The bond angle is less than 109.5 as lone pair- bond pair repulsion is greater than bond pair - bond pair repulsion