C3 - Structure and bonding

Question 1

How are covalent bonds formed?

Answer 1

By atoms sharing electrons

Question 2

What forms covalent bonds?

Answer 2

Non-metals

Question 3

Describe the structure and bonding of a giant covalent substance

Answer 3

Billions of atoms bonded together by strong covalent bonds

Question 4

Describe the structure and bonding of small molecules

Answer 4

• Small numbers of atoms form molecules with strong covalent bonds between them
• Weak IMF between the molecules

Question 5

Describe the structure and bonding of polymers

Answer 5

• Identical molecules joined together by strong covalent bonds in chains
• Weak IMF between chains

Question 6

Why do giant covalent substances have high melting point?

Answer 6

It takes a lot of energy to break the strong covalent bonds between the atom

Question 7

Why do small molecules have low melting points?

Answer 7

Only a small amount of energy is needed to break the weak IMF between molecules

Question 8

Why do large molecules have higher melting and boiling points than small molecules?

Answer 8

Large molecules have stronger IMF so require more energy to break

Question 9

Why do most covalent substances not conduct electricity?

Answer 9

They don’t have delocalised electrons or ions

Question 10

Describe the structure and bonding in graphite

Answer 10

• Each carbon is bonded to three others
• Hexagonal rings in layers
• Delocalised electrons
• Weak forces between layers

Question 11

Why can graphite conduct electricity?

Answer 11

The delocalised electrons are free to move and carry a charge through the substance

Question 12

Why is graphite soft?

Answer 12

Layers aren’t bonded so can slide over each other

Question 13

What is graphene?

Answer 13

One layer of graphite

Question 14

What is a fullerene?

Answer 14

A hollow cage of carbon atoms arranged as a sphere or tube

Question 15

What is a nanotube?

Answer 15

A hollow cylinder of carbon atoms

Question 16

Give two properties of nanotubes

Answer 16

High tensile strength, conducts electricity

Question 17

Give three uses of fullerenes

Answer 17

Lubricants, drug delivery, electronics

Question 18

What is an ion?

Answer 18

An atom that has gained or lost electrons

Question 19

What types of elements form ionic bonds?

Answer 19

Metals and non-metals

Question 20

What charges do elements in group 7 form?

Answer 20

-1

Question 21

What charges do elements in group 1 form?

Answer 21

+1

Question 22

What force holds oppositely charged ions together?

Answer 22

Electrostatic force of attraction

Question 23

Describe the structure of a giant ionic lattice

Answer 23

• Regular
• Alternating positive and negative ions
• Electrostatic forces of attraction

Question 24

Why do ionic substances have high melting points?

Answer 24

Electrostatic forces of attraction are strong and require lots of energy to break

Question 25

Why don't ionic substances conduct electricity when solid?

Answer 25

The ions are fixed in position so can't move. There aren't any delocalised electrons

Question 26

When can ionic substances conduct electricity and why?

Answer 26

When liquid or aqueous. The ions are now free to move and carry a charge

Question 27

Describe the structure of a pure metal

Answer 27

- Layers of positive ions - Delocalised electrons

Question 28

Describe bonding in a pure metal

Answer 28

Strong electrostatic forces of attraction between metal ions and delocalised electrons

Question 29

Why are pure metals malleable?

Answer 29

The layers can slide over each other easily

Question 30

Why do metals have high melting/boiling points?

Answer 30

Electrostatic forces of attraction are strong and require lots of energy to break

Question 31

Why can metals conduct electricity?

Answer 31

The delocalised electrons are free to move and carry a charge through the substance

Question 32

Compare transition metals to groups 1

Answer 32

- TM are harder, stronger, denser and have higher mp/bp - G1 - More reactive

Question 33

What is an alloy?

Answer 33

Mixture of a metal and another element

Question 34

Why are alloys harder than pure metals?

Answer 34

- Different sized atoms disturb the layers - Can't slide anymore

Question 35

How big are nanoparticles?

Answer 35

1-100 nanometres (nm)

Question 36

How are nanoparticles different to bulk materials?

Answer 36

Nanoparticles have a much higher surface area to volume ratio

Question 37

What are nanoparticles used for?

Answer 37

Healthcare, electronics, cosmetics, catalysts

Question 38

How big are fine particles?

Answer 38

100 - 2500 nanometres (nm)

Question 39

How big are coarse particles?

Answer 39

2500 - 10,000 nm (2.5 x 10^-6 - 1 x 10^-5)