3 - Structure and bonding Flashcards
What is ionic bonding?
Ionic bonds are formed between a metal and a non-metal. The ions are held together by electrostatic forces in a giant lattice structure.
Why do ionic compounds have high melting & boiling points?
It takes a lot of energy to break the strong electrostatic forces between the ions.
What are the properties & features of ionic solids?
- Fixed in a giant lattice
- Vibrate but cannot move
- Don’t conduct electricity
What are the properties & features of molten ionic compounds?
- Free ions
- Conducts electricity
What are the properties & features of ionic compounds in solution?
- Water separates ions from the lattice
- Free ions
- Conducts electricity
What is covalent bonding?
Covalent bonds are formed when non-metals react and share their electrons.
What are polymers?
Long chains of molecules that have high melting & boiling points because their intermolecular forces are stronger due to their large size.
What is a giant covalent structure?
Huge networks of atoms held together by strong covalent bonds
What are some substances that are giant covalent structures?
- Diamond
- Graphite
- Silicon dioxide (silica)
What are the properties of giant covalent structures?
- High melting & boiling points
- Insoluble
- Hard
- Don’t carry charge, except graphite
What are the structures of diamond and graphite?
Diamond = each carbon is bonded to 4 other carbons Graphite = each carbon is bonded to 3 other carbons
Why can graphite conduct electricity & heat?
Only three electrons are shared, so there is one mobile, delocalised electron left over that carries charge. The electrons transfer heat to the layers of graphite as they speed up.
What are fullerenes?
A hollow cage of 60 or more atoms.
What are cylindrical fullerenes?
Carbon nanotubes that form thin cylinders with high resistance to tension. They are used to make tennis rackets. They conduct electricity & heat as they have similar bonds to graphite.
What are fullerenes used for?
- Drug delivery
- Lubricants
- Catalysts
What are the properties of graphene?
- Low density
- Strong
- Most reactive form of carbon
- Conductor of heat & electricity
Why can metals form crystals?
They are built up in a regular pattern of layers.
What is metallic bonding?
Metallic bonds are formed as the strong electrostatic forces between the free delocalised electrons and the positive metal ions attract each other.
Why are metals malleable and ductile?
The layers of atoms easily slide over each other.
What is particulate matter?
Larger particles like pollutants, dust or pollen
Why do nanoparticles cause a faster rate of reaction?
They have a larger surface area to volume ratio.
What are nanoparticles used for?
- Titanium oxide nanoparticles react with sun to break down dirt on glass
- Titanium oxide & zinc oxide can be coated with silica to block UV rays
- In cosmetics, they absorb better into the skin
- Deliver drugs directly to the source
- Silver nanoparticles are antimicrobial
- Nanotubes can be used in mini electronic circuits
- Nanotech suits are thin, flexible, tough & contain biosensors
What are the cons of nanoparticles?
- Prone to explosion due to fast rate of reaction
- Inhaling could damage lungs or affect cells if enter bloodstream
What is the difference between nanocages and nanotubes?
Nanocages carry drugs, nanotubes reinforce materials
