4 — chemical bonding, structure and properties of materials

Question 1

Interaction differences betw ionic bonding, metallic bonding and covalent bonding

Answer 1

IB: between cations (metal) and anions (non-metals)

MB: within metal

CB: betw non-metal and non-metal

Question 2

Structure and bonding differences betw ionic bonding, metallic bonding and covalent bonding

Answer 2

IB: giant ionic lattice structure — strong electrostatic forces of attraction between oppositely-charged ions

MB: giant metallic structure — strong electrostatic forces of attraction between positively-charged ions and ‘sea of delocalised mobile electrons’

CB:
simple molecular structure — atoms r held tgt by strong covalent forces but weak intermolecular forces of attraction

Giant covalent structure (eg diamond graphite and silicon dioxide) — strong covalent bonds between atom

Question 3

Difference between melting and boiling points

Answer 3

IB: high melting and boiling point.
- x has a giant ionic structure and hence large amount of energy is needed to overcome the strong electrostatic forces of attraction between oppositely-charged ions

MB: high melting and boiling point
- x has a giant metallic structure and hence large amount of energy is needed to overcome the strong electrostatic forces of attraction between positive metal ions and ‘sea of mobile electrons’

CB:
- low melting and boiling point
- x has a simple molecular structure thus small amount of energy is needed to overcome the weak intermolecular forces of attraction

• high melting and boiling point
• large amount of energy is needed to break the strong covalent bonds between atoms

Question 4

Solubility

Answer 4

IB:
- usually soluble in water but insoluble in organic solvents
- water molecules r attracted to ions which weakens the electrostatic forces betw ions
- ions r pulled from lattice structure and compound dissolves to form aqueous solution

MB: insoluble in both organic solvents and water

CB:
- soluble in organic solvents; insoluble in water

• insoluble in both organic solvents and water

Question 5

Electrical conductivity

Answer 5

IB: conducts electricity in aq and molten state
- due to presence of mobile ions as cations and anions r free to move around
- in solid state, ions vibrate at fixed position and r immobile, hence, there r no mobile ions

MB: conducts electricity in solid state
- presence of ‘sea of delocalised mobile electrons’, thus presence of mobile electrons allow metals to conduct electricity

CB: no electrical conductivity due to absence of mobile ions or mobile electrons

• EXCEPTIONS:
• simple molecular structure: some substances dissociate in water to form aq solutions that conduct electricity
• giant covalent structure — graphite: three strong covalent bonds per carbon atom, fourth outer electron is delocalised hence presence of delocalised mobile electron enables graphite to conduct electricity

Question 6

Extra properties of giant ionic structure

Answer 6

IB: hard but brittle
- the strong electrostatic forces of attraction betw opp-charged ions makes ionic compounds resistant to deforming and hence they tend to be hard
1. When enough force is applied, ions move away from lattice positions and ions of same charge approach each other
2. Repulsive forces betw ions of same charge becomes larger than attractive forces
3. Ionic lattice is deformed of structure and thus shatters

Question 7

Extra properties of giant metallic structures

Answer 7

Malleable and ductile
- malleable: can be hammered, bent or flattened into thin sheets
- ductile: pulled into wire without breaking
- pure metals have a regular structure. The layers of atoms can slide over one another easily without disrupting the metallic bonding when enough force is applied.

Good conductors of heat
- ions are closely packed, proximity of ions allows transfer of heat by vibration quickly from 1 ion to another. Movement of mobile electrons further speed up rate of transfer

Question 8

Extra properties of giant covalent structure

Answer 8

Diamond: hard
- giant molecular structure
- large amount of energy is needed to break the strong covalent bonds betw atoms

Graphite: soft and slippery
- layers of carbon atoms r held tgt by weak intermolecular forces of attraction
- layers of carbon atoms can slide over each other easily
- small amount of energy is needed to overcome the weak intermolecular forces of attraction betw layers of carbon atoms

Question 9

Differences betw bonding diagrams for IB, MB and CB

Answer 9

Go draw it out.