⚠ 2. Bonding, structure, and the properties of matter

Question 1

Three types of chemical bonds

Answer 1

• Ionic
• Covalent
• Metallic

Question 2

Where are the electrostatic forces of attraction in ionic bonds?

Answer 2

Strong electrostatic forces of attraction between the oppositely charged ions

Question 3

Where are the electrostatic forces of attraction in covalent bonds?

Answer 3

Nuclei of two atoms and a shared pair of electrons

Question 4

Where are the electrostatic forces of attraction in metallic bonds?

Answer 4

Nuclei of atoms and delocalised electrons

Question 5

What is an ion?

Answer 5

An atom with a positive or negative charge that has gained or lost electrons to obtain a full outer shell

Question 6

Explain Ionic Bonding in terms of metals and non metals

Answer 6

• When a metal atom reacts with a non-metal atom, electrons in the outer shell of the metal atom are transferred.
• Metal atoms lose electrons to become positively charged ions. Non-metal atoms gain electrons to become negatively charged ions.

Question 7

Dot and Cross Diagram

& Limitations

Question 8

Ionic Compounds & Properties

Answer 8

• Form Giant regular structures known as a giant ionic lattice
• Strong electrostatic forces of attraction in all directions between oppositely charged ions
• High melting & boiling points because lots of energy is needed to break down the strong bonds
• Can only conduct electricity in molten or liquid form because the ions are free to move so charge can flow

Question 9

Ball and Stick Diagram

& Limitations

Question 10

2D + 3D Diagrams

& Limitations

Question 11

What is Covalent Bonding?

Answer 11

The sharing of pairs of electrons between non-metal atoms

Note: A molecule is a group of two or more atoms joined together by covalent bonds

Question 12

Which type of bond are molecules?

Answer 12

Covalent bonds

Question 13

Properties of Covalent Bonds

& small molecules

Answer 13

• Covalent Bonds are strong bonds
• Covalent Bonds have weak intermolecular forces
• Small molecules are usually gases or liquids that have low melting or boiling points because the weak intermolecular forces are easily overcome
• The larger the molecules are, the stronger the intermolecular forces, so the melting and boiling points increase
• They cannot conduct electricity because the molecules have no overall charge

Question 14

Giant Covalent Structures & Properties

Answer 14

They are many atoms joined together by covalent bonds in a giant lattice structure
- High melting and boiling points as there are a large number of bonds to be broken in a giant covalent structure, and all the bonds are linked by strong covalent bonds

Question 15

Examples of Giant Covalent Structures

Answer 15

Diamond, Graphite ( + graphene ), and silicon dioxide

Question 16

Diamond & Properties

Answer 16

• A giant covalent structure
• Each carbon atom is bonded with 4 other carbon atoms
• Does not conduct electricity
• Rigid network held together by stong covalent bonds, so:
  • It is hard enough to resist forces that could distort the structure
  • It has a very high melting and boiling point

Question 17

Graphite & Properties

Answer 17

• A giant covalent structure
• Has hexagonal rings in layers
• There are weak intermolecular forces between the layers which means that the layers can slide past each other - making graphite soft and slippery
• Each carbon atom is bonded with 3 other carbon atoms
• Carbon has 4 electrons - 3 are bonded - so there is one delocalised electron for each carbon atom in graphite
• Delocalised electrons mean that they are free to move so they can conduct electricity and heat

Question 18

Graphene & Properties

Answer 18

A single layer of graphite so it is transparent and flexible

• Strong covalent bonds which means:

• High melting point
• Very strong - useful for making composites

• Has delocalised electrons so it conducts electricity - useful in electronics

Question 19

Fullerenes

& Examples

Answer 19

Molecules of carbon atoms with hollow shapes ( such as tubes, balls and cages )

• Fullerenes have a structure of hexagonal rings with 5, 6 or 7 carbon atoms

Examples: Buckministerfullerene (C60), Carbon Nanotubes

Question 20

Buckministerfullerene

Answer 20

• Consists of 60 carbon atoms
• Each atom bonded to 3 other carbon atoms
• Arranged in rings of 5-6 atoms (pentagons & hexagons)
• Weak intermolecular forces between the molecules of buckministerfullerene, so it is slippery
• Because it is slippery and spherical, it is useful for lubricants

Question 21

Carbon Nanotubes

Answer 21

• Cylindrical fullerenes
• Very high length to diameter ratios - ( Very long compared to their width )
• This makes them useful for nanotechnology, electronics and materials (they conduct electricity)

Question 22

Polymers

Answer 22

• Polymers have very large molecules
• They are linked to other atoms by strong covalent bonds
• The intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature.

Question 23

What is metallic bonding?

• How are they organised?
• Talk about their attraction

Answer 23

Metallic bonding is the bonding of metal atoms

• It consists of a giant structure of metal atoms - which are positive ions - and a sea of delocalised electrons which are free to move through the structure
• The sharing of delocalised electrons results in strong metallic bonds.

Question 24

Properties of metals

Answer 24

• High melting and boiling points as lots of energy required to break a number of strong metallic bonds
• Metals are good conductors of electricity because the delocalised electrons in the metal carry electrical charge through the metal.
• Metals are good conductors of thermal energy because energy is transferred by the delocalised electrons.
• Particles in pure metals have a regular arrangement and size, so the layers are able to slide over each other, resulting in them being malleable (bent) and ductile (pulled/shaped)

Question 25

Alloys

• What is it?
• Why is it used?
• An example

Answer 25

• An alloy is a mixture of two or more elements
• Pure metals are too soft for many uses due to their regular arrangement and size
• They are mixed with other metals to make alloys, which are harder because the different-sized atoms distort the layers to slide over each other
• Steel is an alloy made of iron and small amounts of carbon

Question 26

Nanoscience & Nanoparticles

Answer 26

• Nanoscience is the study of structures that are between 1 and 100 nanometres (nm) in size.
• Nanoparticles are only a few hundred atoms in size
• They have a high surface area to volume ratio

Question 27

Nanoparticle Uses

Advantages & Disadvantages

Answer 27

• Electronics - They have high length to diameter ratio
• Sun Creams - They are small in size so are invisible to skin. However, it is difficult to see where it has been applied as it is invisible to skin
• Deodorants - High surface area to volume ratio
• Catalysts - High surface area to volume ratio

Question 28

Where does ionic bonding occur?

Answer 28

Occurs in compounds formed of metals combining with non-metals

Question 29

Where does covalent bonding occur?

Answer 29

Occurs in compounds of non metals

Question 30

Where does metallic bonding occur?

Answer 30

Occurs in metallic elements and alloys