Covalent substances

Simple molecular substances
1. The atoms form very strong covalent bonds to form small molecules of several atoms.
2. By contrast, the forces of attraction between these molecules are very weak.
3. The result of these week intermolecular forces is that the melting and boiling points are very low.
  1. This is because the molecules are easily parted from each other.
4. Most molecular substances are gasses or liquids at room temperature, but they can be solids.
5. Molecular substances don't conduct electricity - there are no ions so no electrical charge.
Giant covalent structure (macromolecules)
1. These are similar to giant ionic structures (lattices) except that there is no charged ions.
2. All the atoms are bonded to each other by strong covalent bonds.
3. They have very high melting and boiling points.
4. They don't conduct electricity (except from graphite)
5. The main examples are diamond and graphite, which are only made from carbon atoms.
6. Diamond
  1. Each carbon atom forms 4 covalent bonds in a very rigid structure.
    1. This makes diamond very hard.
7. Graphite
  1. Each carbon atom forms 3 covalent bonds. This creates layers which are free to slide over each other.
    1. This makes graphite soft and slippery.
  2. The layers are held together so loosely that they can be rubbed off onto paper (pencil).
  3. Graphite is the only non-metal which is a good conductor of heat and electricity.
    1. Each carbon atom has 1 delocalised (free) electron and its these free electrons that conduct the electricity and heat.

Next up

Covalent substances

Description

Resource summary

Similar

	Created by jessica-gollop about 11 years ago