2.2 Simple molecules
Atoms within molecules are held togehter by strong covalent bonds, these bonds only act between atoms within molecules so simple molecules have little attraction for each other.
Substances made of simple molecules have realtivley low melting points and boiling points.
they do not conduct electricity because the molecules dont have an overall charge so they cant carry one.
2.3 Giant covalent structures
Giant covalent structures or macromolecules.
Every atom is bonded to sevelra other atoms by stong covalent bonds therefore they have high melting and boiling points because it takes a huge amount of energy to break down the lattice structure.
DIAMONDS - Formed of carbon and has a 3D giant structure. Every carbon atom is covalently bonded by 4 other atoms, this makes it hard and transparent. Silicon dioxide (sillica) has a similar structure.
GRAPHITE - Formed of carbon atoms and is covalently bonded by three other carbo atoms in a giant flat 2d layers. NO covalent bonds between layers making graphite slipperey and grey because the layers slide over each other. Graphite can conduct electricity.