Foundation tier Flashcards
How are covalent Bonds formed?
Sharing of electrons
Which type of atoms form covalent bonds between them?
Non-metals
What are the two structures that arise from covalently bonded non-metals?
small molecules - strong covalent bonds between atoms and weak intermolecular forces between molecules.
Giant covalent Lattice - strong covalent bonds throughout the structure.
Why do giant covalent substances have high melting and boiling points?
It takes alot of energy to overcome the strong covalent bonds between the atoms.
Why do small molecules have low melting and boiling points?
Only a small amount of energy is needed to overcome the weak intermolecular forces between molecules.
Why does the melting and boiling point increase as the small molecules get bigger?
The weak intermolecular forces between the molecules get stronger.
Why do most covalent substances not conduct electricity?
They do not have delocalised electrons.
Describe the structure and bonding in graphite?
Each carbon is bonded to three other carbon atoms.
They arranged in hexagonal rings in layers.
It has delocalised electrons
It has weak intermolecular forces between the layers but Strong covalent bonds within each layer.
Why is graphite soft?
The layers slide over each other.
What is graphene?
One layer of graphite
Give two properties of graphene?
Strong, conducts electricity, light
What is a fullerene?
An allotrope of carbon - a hollow cage arranged as a sphere or tube
What is a nanotube?
A hollow cylinder of carbon atoms
Give two properties of nanotubes?
High tensile strength, conduct electricity.
Give three uses of fullerenes?
lubricants, drug delivery, high-tech electronics.
