- A bond between two non-metal atoms. They bond by sharing electrons to complete their outer energy levels.
- They are held together by strong forces of attraction of the shared electrons to the nuclei.
- This can be expressed for molecules in diagrams:
e.g. Methane CH4
- There are two types of covalent structures:
- Simple molecular structures
- Giant covalent structures
Simple Molecular Structures
- Simple molecular structures are held together by weak intermolecular forces, formed when e- move towards one end of the atom.
Properties of Simple Molecular Structures
- Low MP & BP - Weak intermolecular forces easily overcome
- Does not conduct electricity
- Does not dissolve in water, but may in some organic solvents.
Giant Covalent Structures
- Held together by many strong covalent bonds, which require energy to break, meaning high MP & BP.
- Graphite - Each carbon atom is bonded to three other carbon atoms.
- The layers are held together by weak intermolecular forces - therefore soft, slippery substance
- Graphite can be used as lubricant due to its structure.
- Diamond - Each carbon atom has a complete outer energy level and is bonded to four other carbon atoms.
- It is the hardest known substance, is used for cutting. It has a high MP due to the many strong covalent bonds.