Unit 3 Part 6 - 2.2.7 - Covalent network structure

Question 1

What are covalent network structures also known as?

Answer 1

Giant molecular or macromolecular structures

Question 2

What is a covalent network structure?

Answer 2

The crystal thats a single molecule w/ a regular repeating pattern of covalent bond, so has no finite size

Question 3

What are allotropes?

Answer 3

They have different bonding and structural patterns of the same elements in the same physical state
- Therefore have diff chemical and physical properties

Question 4

What are the different types of allotropes of carbon?

Answer 4

1. Diamond
2. Graphite
3. Graphene
4. C60 Fullerene

Question 5

Structure of diamond?

Answer 5

1. Each c atom = SP3 hybridized
2. Covalently bonded with 4 others
3. Tetrahedral
4. Bond angle of 109.5

Question 6

Electrical conductivity of diamond?

Answer 6

Doesn’t conduct electricity
- All electrons bonded = non-mobile

Question 7

Thermal conductivity of diamond?

Answer 7

V efficient thermal conductor
- Better than metals

Question 8

Appearance of diamond?

Answer 8

V transparent and lustrous crystal

Question 9

Physical and chemical properties of diamond?

Answer 9

1. Hardest known natural substance
2. Brittle
3. V high M.P

Question 10

Uses of diamond?

Answer 10

1. Grinding/ cutting glass
2. Jewellery

Question 11

Structure of Graphite?

Answer 11

1. Each c atom = SP2
   - Covalently bonded to 3 forming hexagons
2. Bond angle =120

Question 12

What happens to the remaining valence electron on each carbon in graphite?

Answer 12

They are delocalized so it can move freely across layer

Question 13

What are the layers in graphite held by?

Answer 13

Weak London dispersion forces

Question 14

Electrical conductivity of Graphite?

Answer 14

Good conductor
- Has 1 non-bonded, delocalized electron per atom that provides electron mobility

Question 15

Thermal conductivity of Graphite?

Answer 15

Not good conductor

Question 16

Physical and chemical properties of Graphite?

Answer 16

1. Soft and slipper
   - B/c of slippage of layers over each other
2. Brittle
3. V high M.P
4. Most stable allotrope of carbon

Question 17

Uses of Graphite?

Answer 17

1. Dry lubricant
2. Pencils

Question 18

Structure of Graphite?

Answer 18

1. Each c atom = SP2
   - Covalently bonded to three others making hexagobs
2. Bond angles of 120
3. Single layer (2D)
4. Remaining valanece electron is delocalized

Question 19

Conductor of graphene?

Answer 19

V goo conductor
- One delocalized electron per atom gives electron mobility for all layers

Question 20

Thermal conductivity of graphene?

Answer 20

Best conductivity

Question 21

Appearance of graphene?

Answer 21

Basically transparent

Question 22

Physical and chemical properties of graphene?

Answer 22

1. Thinnest material ever
2. Strongest material ever
3. V flexible
4. V high M.P

Question 23

Uses of graphene?

Answer 23

Transmission electron microscopy grids

Question 24

Structure of C60 Fullerene?

Answer 24

1. Each c atom = SP2
   - Bonded to sphere of 60 c atoms making 12 pentagons and 30 hex
2. Closed sphere cage

Question 25

Why is 60Fullerene not a giant molecule?

Answer 25

B/c it has a fixed formula

Question 26

Electrical conductivity of c60Fullerene?

Answer 26

Poor - Little electron movement in delocalized electrons

Question 27

Thermal conductivity of c60Fullerene?

Answer 27

V low

Question 28

Appearance of C60 Fullere?

Answer 28

Black powder

Question 29

Physical and chemical properties of c60Fullerene?

Answer 29

1. V light +strong 2. Reacts w/ K to make super conducting crystalline material 3. Low M.P

Question 30

What is nanotechnology?

Answer 30

The study that deals w/ the atomic scale manipulation of matter