Topic 4&14 Chemical Bonding and Structure (4.5, 14.1, 14.2)

Question 1

4.5 What is metallic bonding?

Answer 1

Electrostatic attraction between a lattice of positive ions and delocalised electrons

Question 2

4.5 How does the charge and size of the ions relate to metallic bond strength?

Answer 2

More delocalised electrons= higher charge and smaller cation= stronger bond (also higher mp & bp)

Question 3

4.5 Why are metals malleable?

Answer 3

Ions are free to slide over each other in a sea of delocalised electrons

Question 4

4.5 For conductivity to occur, substances must possess…

Answer 4

Electrons or ions that are free to move and metals contain delocalised electrons so they are excellent conductors

Question 5

4.5 What property of metals allow thermal conductivity?

Answer 5

Delocalised electrons and closely packed cations allow transfer of heat energy

Question 6

4.5 What are alloys?

Answer 6

Metal made by combining two or more metallic elements with non-directional bonding (due to different element sizes, makes it more difficult for atoms to slide over each other)

Question 7

4.5 Comparison of metals and alloys?

Answer 7

Alloys are less malleable and doesn’t slip under stress, they are also more chemically stable, stronger and more resistant to corrosion (because of non-directional bonding)

Question 8

4.5 How does the charge and size of the ions relate to metallic bond strength?

Answer 8

More delocalised electrons= higher charge and smaller cation= stronger bond (also higher mp & bp)

Question 9

4.5 Why are metals malleable?

Answer 9

Ions are free to slide over each other in a sea of delocalised electrons

Question 10

4.5 For conductivity to occur, substances must possess…

Answer 10

Electrons or ions that are free to move and metals contain delocalised electrons so they are excellent conductors

Question 11

4.5 What property of metals allow thermal conductivity?

Answer 11

Delocalised electrons and closely packed cations allow transfer of heat energy

Question 12

4.5 What are some examples of alloys and what is the composition?

Answer 12

Steel (iron, carbon and other elements)
Sterling silver (silver and copper)
Brass (copper and zinc)

Question 13

4 Arrange the three intramolecular forces in order of increasing strength and give reason.

Answer 13

Metallic < Ionic < Covalent
Metallic is the weakest because it involves 2 weak electronegative atoms white covalent has 2 strong ones, ionic has 1 each.

Question 14

4 What affects the bond strengths of each of the intramolecular forces?

Answer 14

• Covalent: bond lengths, shorter= stronger
• Ionic: smaller ions and greater charge on the ions= greater attraction
• Metallic: more positive the nucleus and more electrons= better

Question 15

4 Arrange the three intermolecular forces in order of increasing strength and give reason.

Answer 15

London < Dipole-diple < Hydrogen
London is the weakest because it is only present in non-polar molecules, dipole-dipole involves 2 polar molecules, hydrogen bonding has 1 highly en element and H.

Question 16

4 What affects the bond strengths of each of the intermolecular forces?

Answer 16

• Hydrogen: more polar= stronger
• Dipole-dipole: more polar= stronger
• London: more electrons= stronger