3 - Structure and bonding

Question 1

What is ionic bonding?

Answer 1

Ionic bonds are formed between a metal and a non-metal. The ions are held together by electrostatic forces in a giant lattice structure.

Question 2

Why do ionic compounds have high melting & boiling points?

Answer 2

It takes a lot of energy to break the strong electrostatic forces between the ions.

Question 3

What are the properties & features of ionic solids?

Answer 3

• Fixed in a giant lattice
• Vibrate but cannot move
• Don’t conduct electricity

Question 4

What are the properties & features of molten ionic compounds?

Answer 4

• Free ions

- Conducts electricity

Question 5

What are the properties & features of ionic compounds in solution?

Answer 5

• Water separates ions from the lattice
• Free ions
• Conducts electricity

Question 6

What is covalent bonding?

Answer 6

Covalent bonds are formed when non-metals react and share their electrons.

Question 7

What are polymers?

Answer 7

Long chains of molecules that have high melting & boiling points because their intermolecular forces are stronger due to their large size.

Question 8

What is a giant covalent structure?

Answer 8

Huge networks of atoms held together by strong covalent bonds

Question 9

What are some substances that are giant covalent structures?

Answer 9

• Diamond
• Graphite
• Silicon dioxide (silica)

Question 10

What are the properties of giant covalent structures?

Answer 10

• High melting & boiling points
• Insoluble
• Hard
• Don’t carry charge, except graphite

Question 11

What are the structures of diamond and graphite?

Answer 11

Diamond = each carbon is bonded to 4 other carbons
Graphite = each carbon is bonded to 3 other carbons

Question 12

Why can graphite conduct electricity & heat?

Answer 12

Only three electrons are shared, so there is one mobile, delocalised electron left over that carries charge. The electrons transfer heat to the layers of graphite as they speed up.

Question 13

What are fullerenes?

Answer 13

A hollow cage of 60 or more atoms.

Question 14

What are cylindrical fullerenes?

Answer 14

Carbon nanotubes that form thin cylinders with high resistance to tension. They are used to make tennis rackets. They conduct electricity & heat as they have similar bonds to graphite.

Question 15

What are fullerenes used for?

Answer 15

• Drug delivery
• Lubricants
• Catalysts

Question 16

What are the properties of graphene?

Answer 16

• Low density
• Strong
• Most reactive form of carbon
• Conductor of heat & electricity

Question 17

Why can metals form crystals?

Answer 17

They are built up in a regular pattern of layers.

Question 18

What is metallic bonding?

Answer 18

Metallic bonds are formed as the strong electrostatic forces between the free delocalised electrons and the positive metal ions attract each other.

Question 19

Why are metals malleable and ductile?

Answer 19

The layers of atoms easily slide over each other.

Question 20

What is particulate matter?

Answer 20

Larger particles like pollutants, dust or pollen

Question 21

Why do nanoparticles cause a faster rate of reaction?

Answer 21

They have a larger surface area to volume ratio.

Question 22

What are nanoparticles used for?

Answer 22

• Titanium oxide nanoparticles react with sun to break down dirt on glass
• Titanium oxide & zinc oxide can be coated with silica to block UV rays
• In cosmetics, they absorb better into the skin
• Deliver drugs directly to the source
• Silver nanoparticles are antimicrobial
• Nanotubes can be used in mini electronic circuits
• Nanotech suits are thin, flexible, tough & contain biosensors

Question 23

What are the cons of nanoparticles?

Answer 23

• Prone to explosion due to fast rate of reaction

- Inhaling could damage lungs or affect cells if enter bloodstream

Question 24

What is the difference between nanocages and nanotubes?

Answer 24

Nanocages carry drugs, nanotubes reinforce materials