Forming bonds (AQA GCSE Chemistry): Revision Notes
Forming bonds
What are chemical bonds?
Noble gases are unreactive because they have full outer electron shells. But atoms of other elements need to form bonds to get full outer shells. There are three main types of strong chemical bonds.
Ionic bonds
Ionic bonds form when metals react with non-metals.
How ionic bonds work:
- Metal atoms lose their outer electrons
- These electrons transfer to the non-metal atoms
- This creates oppositely charged ions
- The metal becomes a positive ion
- The non-metal becomes a negative ion
- The opposite charges attract strongly
Example: Sodium and Chlorine Reaction
When sodium reacts with chlorine, sodium loses an electron and chlorine gains it. This makes and ions that attract each other.
Key fact: Ionic bonds are very strong.
Covalent bonds
Covalent bonds form when non-metal atoms join with other non-metal atoms.
How covalent bonds work:
- The atoms share electrons between them
- This sharing gives both atoms a full outer shell
- The shared electrons create a strong bond
- Covalent bonds are found in non-metal elements and compounds
Example: Hydrogen Chloride Formation
In hydrogen chloride (), hydrogen and chlorine share electrons.
Key fact: Covalent bonds between atoms are strong.
Metallic bonds
Metallic bonds form in metals and metal alloys.
How metallic bonds work:
- Metal atoms lose their outer shell electrons
- This creates positive metal ions
- The ions arrange in a regular 3D pattern called a lattice
- The electrons can move freely throughout the lattice
- This creates strong bonding between the ions and electrons
Key fact: Metallic bonds are strong.
Naming simple compounds
When you know what elements are in a compound, you can name it:
Examples of Simple Compound Names
- Hydrogen sulfide () - contains hydrogen and sulphur only
- Potassium nitrate () - contains potassium, nitrogen and oxygen
You need to know the names and symbols of the first 20 elements, plus compounds made from Group 1 and Group 7 elements.
Key Points to Remember:
- Ionic bonds form between metals and non-metals through electron transfer
- Covalent bonds form between non-metals through electron sharing
- Metallic bonds form in metals with freely moving electrons in a lattice
- All three types of bonds are strong
- Noble gases don't need to bond because they already have full outer shells