2 Bonding 3

Question 1

Describe the main features of metals in terms of their structure

Answer 1

Positive metal ions arranged in layers with delocalised electrons

Question 2

Explain why metals can conduct electricity

Answer 2

Delocalised electrons are free to carry charge

Question 3

Explain why pure metals are soft

Answer 3

Layers of metal ions are free to slide over each other

Question 4

What is an alloy?

Answer 4

A mixture of two or more elements, at least one of which is a metal

Question 5

Give a reason for alloying a metal

Answer 5

To make it harder, to make it less reactive

Question 6

Explain why alloys can be harder than pure metals

Answer 6

Different size of atoms disturb the layers to stop them sliding over each other

Question 7

What are the three types of chemical bond?

Answer 7

Ionic, covalent and metallic

Question 8

Which type of bonding involves electrostatic attractions between oppositely charged ions?

Answer 8

Ionic

Question 9

What is the definition of a covalent bond?

Answer 9

A shared pair of electrons

Question 10

Why is aluminium a better electrical conductor than sodium?

Answer 10

Aluminium is in group 3, so each atom contributes 3 electrons to the delocalised sea of electrons, leaving behind a 3+ ion. There are more electrons in the sea than sodium, so it is a better conductor.

Question 11

Why are alloys stronger than pure metals?

Answer 11

There are different sized atoms in the structure which distorts the layers and stops them being able to slide over each other.

Question 12

Put these bonds in order of strength starting with the weakest: ionic, covalent, metallic

Answer 12

Weakest metallic, then ionic, covalent strongest

Question 13

How does the charge on the ions produced by the metals in groups 1, 2 and 3 relate to their group number?

Answer 13

It is positive and the same as the group number

Question 14

How the charge on the ions produced by the non-metals in groups 5, 6 and 7 realte to their group number.

Answer 14

It is equal to the group number minus 8.

Question 15

Describe the structure of sodium chloride and explain why it has a high boiling point.

Answer 15

It is a 3D lattice of 1+ sodium ions and 1- chloride ions. The electrostatic force between the oppositely charged ions is high, so the bonds are strong. There are many bonds. A lot of energy is needed to overcome the ionic bonds.

Question 16

What type of structures do water, ammonia and iodine have?

Answer 16

Simple molecular (or simple molecules)

Question 17

What are the three states of matter?

Answer 17

solid, liquid and gas

Question 18

What type of bonds hold the long chain together in polymers?

Answer 18

Covalent

Question 19

How many bonds does each carbon have in graphite?

Answer 19

3

Question 20

What is graphene made from? Describe its structure.

Answer 20

A single layer of carbon atoms in a graphitre structure.

Question 21

Ammonia is a liquid between -77.7 oC and
-33.3oC. Use the kinetic theory to explain
the three states of matter in this case.

Answer 21

Below -77.7 degrees the particles are close together and only vibrate, ammonia is a solid. If the temperature is above -77.7 degrees but below -33.3 the particles are close together but able to move, ammonia is a liquid. Above -33.3 the forces between the molecules have been overcome and they are free to move around, ammonia is a gas.

Question 22

Diamond coating would make smartphones and tablets far stronger but would remove their touch-screen capability. Use your knowledge of bonding to explain why.

Answer 22

Diamond is a giant covalent structure. All the electrons are shared in bonds and not able to move and carry charge. If the screen has a diamond coating it cannot conduct and will not work.

Question 23

Explain why the ball and stick model is not a true representation of the structure of an ionic compound.

Answer 23

The ions are not spread apart they are close together, so the sticks are misleading. The ions are not always ball shaped and may be different sizes, so the balls are also misleading.

Question 24

Sulphur hexafluoride SF6 is an insulating gas. Suggest the type of bonding present and explain why it is gaseous at STP (Standard Temperature and Pressure).

Answer 24

Covalent bonding as S and F are non-metals. There ould be weak intermolecular forces between each molecule.