Covalent bond
- non-metal + non-metal
- shared pair of electrons
Ionic bond
- non-metal + metal
- attraction between oppositely charged ions
Metallic bond
- metal + metal
- positive metal ions + delocalised electrons
Ionic compounds structure
Giant ionic lattice
What makes up a giant lattice
Strong electromagnetic forces of attraction between oppositely charged ions
Ionic bonds all have
High melting points
High boiling points
What happens when ionic compounds melt?
Ions are free to move and carry electric charge
How are covalent bonds made
+ charged nuclei of bonded atoms are attracted to the shared pair of electrons by electrostatic forces - making them very strong
what are simple molecular substances made up of?
molecules containing atoms joined together by covalent bonds
strong covalent bonds =
forces of attraction are weak
do molecular compounds conduct electricity?
no, they are not charged so there are no free electrons or ions
polymer
large, chain-like molecules composed of repeating smaller units called monomers
linked together by strong covalent bonds
why are most polymers solid at room temperature?
intermolecular forces between polymer molecules are larger than between simple covalent molecules, so more energy is needed to break them
diamond covalent structure
each carbon atom forms 4 covalent bonds in a very rigid structure
graphite covalent structure
each carbon atom forms 3 covalent bonds to create layers of hexagons.
each carbon atom also has 1 delocalised electron
silicon dioxide covalent structure
‘silica’
what sand is made of
each grain of sand is 1 giant structure of silicon and oxygen
graphene
1 layer of graphite
fullerenes use
‘cage’ other molecules
forms around another atom or molecule which is then trapped inside
can be used to deliver drug into body
what are fullerenes
molecules of carbon shaped like closed tubes or hollow balls
alloy
mixture of 2 or more metals, or a metal and another element
