Ionic bonding is the electrostatic attraction between positive and negative ions. It is a relatively strong attraction.

• They are held together in a giant lattice.
• It's a regular structure that extends in all directions in a substance.
• Electrostatic attraction between positive and negative ions holds the structure together.

• High melting and boiling point (strong electrostatic forces between oppositely charged ions)
• Do not conduct electricity when solid (ions in fixed positions).
• Conduct when molten or dissolved in water - ions are free to move.

Reaction of a metal with a non-metal.
Electron transfer occurs - metal gives away its outer shell electrons to non-metal.
Mg is in Group II, so has 2 available outer shell electrons.
O is in Group VI, so can accept 2 electrons to get a full outer shell configuration.
Mg becomes Mg^2+ and O becomes 0^2- (oxide).

How are ionic compounds formed? Explain in terms of MgO case

Covalent bond is a shared pair of electrons between two atoms

- Do not conduct electricity (no ions)
- Small molecules
- Weak intermolecular forces, therefore:
- Low melting and boiling points

Describe the structure and properties of simple molecular covalent substances 

They increase. That causes melting/boiling points to increase as well (more energy needed to overcome these forces)

How do intermolecular forces change as the mass/size of the molecule increases?

-Polymers are very large molecules (>100s, 1000s of atoms) with atoms linked by covalent bonds.
-Thermosoftening polymers - special type of polymers; they melt/soften when heated. There are no bonds between polymer chains. Strong intermolecular forces ensure that the structure is solid at room temperature. These forces are overcome with heating - polymer melts.

What are polymers? What are thermosoftening polymers?

-Solids, atoms covalently bonded together in a giant lattice.
- High melting/boiling points - strong covalent bonds.
- Mostly don't conduct electricity (no delocalised é)
- Diamond, graphite, silicon dioxide.

What are giant covalent substances? Give examples 

- four, strong covalent bonds for each carbon atom
- very hard (Strong bonds)
- very high melting point (strong bonds)
- does not conduct (no delocalised electrons)

Describe the properties of diamond (allotrope of carbon)

- three covalent bonds for each carbon atom
- layers of hexagonal rings
- high melting point
- layers free to slide as weak intermolecular forces between layers; soft, can be used as a lubricant
- conduct thermal and electricity due to one delocalised electron per each carbon atom

Describe the properties of graphite (allotrope of carbon)

- hollow shaped molecules
- based on hexagonal rings but may have 5/7-carbon rings
- C60 has spherical shape, simple
molecular structure (Buckminsterfullerene)

Describe the properties of fullerenes (allotrope of carbon)

- cylindrical fullerene with high length to diameter ratio
-High tensile strength (strong bonds)
-Conductivity (deloc. electrons)

Describe the properties of nanotubes (allotrope of carbon)

Describe the properties of graphene (allotrope of carbon)

Forces of attraction between delocalised electrons and nuclei of metal ions.

- High melting/boiling points (strong forces of attraction)
-Good conductors of heat and electricity (delocalised electrons)
- Malleable, soft (layers of atoms can slide over each other whilst maintaining the attraction forces)

Alloys:
- mixtures of metal with other elements, usually metals
-different sizes of atoms distorts the layers, so they can't slide over each other, therefore alloys are harder than pure metals

What are alloys? Why are they harder than pure metals?

Low, because of weak intermolecular forces between molecules 

Simple Covalent compounds boiling and melting points 

High, because of giant lattice of ions with strong forces between oppositely charged ions

Ionic compounds  boiling and melting points

High, strong electrostatic forces between positive ions and delocalised electrons 

Metallic compounds boiling and melting points 

Simple covalent molecules conductivity when solid

Diamond and sand conductivity when solid (Giant covalent)

Good, as free delocalised electrons between layers can move through the structure 

Bonding and structure

Flashcards

year 9 chemistry

GCSE AQA Chemistry paper 2

year 8 chem flashcards /questions

Bonding and structure

Flashcards

year 9 chemistry

GCSE AQA Chemistry paper 2

year 8 chem flashcards /questions